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FORECASTERS FRET, SNOW-LOVERS SULK, CRITICS CONDEMN...AS ONE STORM FIZZLES ANOTHER RIDES A VERY FINE LINE FOR LATE THIS WEEK

Welcome to the weather blog - a regular Monday through Friday discussion of the weather!  While the discussions usually will only come on days I'm working, I'll issue special updates when the weather warrants.  I will always post to let you know when no discussion is expected if I'm away on vacation, etc. - if no update is here and no info is available, that likely means the server has temporarily gone on the fritz and I will update as soon as technically possible.  You'll find a quick weather synopsis linked to the daily forecast at the top of the page, a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow by mid-afternoon. My email is contact@mattnoyes.net.  This blog is for you, so I hope you enjoy it!  -Matt Noyes

General Weather Summary:

Heartbreaking!  That's the best description for Southern New England snow lovers (and meteorologists) awakening to much less snow than was predicted to fall by Wednesday morning.  Instead of bands of widespread snow with a developing storm tapping Atlantic moisture, localized bursts of snow were all we could muster, delivering an inch or two to some, a dusting to many, and nothing at all to others.  For yours truly, I awakened extra-early to face the early-morning drive in, and ran to the window like a schoolboy, with my eager smile quickly wiped away to find barely a flake had fallen outside my window.  On a brighter note, this extra time was handy when I realized halfway to work that I'd forgotten my suit jacket and tie, and had to go back home to get 'em!  While the missed snow event is a blessing for some, it is undoubtely a curse for others whose livelihood depends on clearing snow, and while treatments were required for many areas, I'm aware of the headaches the LACK of snow has caused many folks.  The cause of this forecast "bust" was the sluggish nature of the energy center to pick up Atlantic moisture as it passed south of New England, not picking up necessary moisture until it was south of Block Island - too late to deliver appreciable snow.

Later Wednesday, as the storm pulls quickly away from New England, a few snow showers are likely to linger in the mountains while the remainder of New England finds breaks of sun and breezy, cool conditions.  This break in the action will last into Thursday, after a partly cloudy and cold Wednesday night with a noticeable increase in clouds late, before another disturbance moves toward New England later Thursday.  Contrary to its predecessors, this storm will have plenty of moisture thanks to a track that will bring the storm near the Gulf of Mexico coastline before it prepares to wrap northward and redevelops off the Atlantic Seaboard.  The most likely scenario is for snow to overspread some of New England Thursday night well in advance of the main storm center, then become heavier heading into Friday.  At this point - given ocean water temperatures still running in the 40s in the open ocean south and east of New England - it's likely that at least some warm air will be carried northward with this storm that may result in a mix with and perhaps change to rain in far southeastern New England on Friday.  I'm not sold on this warmth penetrating too far north, though, largely because of what I discussed at the start of this discussion, which is the cold airmass well in place across Northern New England.  This is not only cold but also quite dense and stubborn and will not budge even with approach of warmth from the south.  The result will likely be for easterly winds to become more northeasterly Thursday night into Friday, resulting in a very slow northward progression of any rain/snow line.  That said, I'm also not completely sold on bringing gobs of precipitation into New England.  Though we have a deep "trough," or dip in the jet stream, that keeps us cold, this also keeps storms rather flat.  With a recent pattern of keeping storms to our south, it would take a significant deviation in the storm track to bring the snow shield deep into New England, and that's a tough sell to make when I'm still looking at a broad trough that would favor southward suppression of the storm.  At this point, therefore, I'm willing to bring snow showers that will morph into a shield of snow Thursday night into early Friday, though I'm not sold on more than a few inches in the higher amounts, except perhaps in Southeastern New England, just on the cold side of the rain/snow line where locally higher amounts could occur.  That's not a hard and fast forecast for the storm so much as my thoughts on how it should evolve, given the pattern.  With New England riding so close to such deep moisture, it's still a bit early for any numbers to start flying around in forecasts.

This weekend will bring another disturbance Friday night - capable of a few renewed snow showers - then colder air gradually moving southward through New England on Saturday with an active wind, but mostly dry in many areas excepting snow showers in the Northern Mountains.  Another disturbance Saturday night will move over New England and drag an associated reinforcing surge of cold air at the surface, perhaps bringing a few more snow showers for many overnight Saturday night, then locking in the cold for Sunday.

In the longer range, the second and third weeks of February will bring a shift in the pattern that will result in shrinking the overall coverage of deep cold over the Lower 48, but will also help to nudge the axis of coldest air west just a bit, over the Great Lakes and Ohio Valley, which would allow moisture to stream northward over the Eastern Seaboard.  In essence, this should theoretically allow for the storms that have been blasting off just off the coastline the past few weeks to begin taking off near or over the coastline as we round the corner into February.  This is something worth watching.

For what it's worth, I was skiing last weekend in New Hampshire and the conditions were fantastic, and reports from ALL New England states are just as stellar.  Anyone considering not skiing because of fear of conditions is worried for no reason - the man-made conditions are amazing and worth the trip.  No, I'm not being paid by the ski areas to say it - just a long-time New England skier who loves to share the news!

Have a great hump day!

Matt

Matt's Technical Meteorological Discussion: Updated Wednesday, January 31 at 2:10 PM

What a bust!  There are two sides to a busted forecast - one is the public side and the other is the technical.  I am all about being willing to apologize on the public side, and acknowledge where a forecast went wrong, as long as it doesn't take away from your ability to adequately cover the weather that lay ahead.  From a technical standpoint, this discussion was written briefly yesterday but with authority - that is, I felt quite certain of how the situation would unfold.  Oddly enough, I was reminded by fellow meteorologist Jodie Frazee here at NECN of my comments at the end of the day..."Of course, you know, there is another possibility with this storm.  This shows low potential of a center-jump that would nearly bypass New England entirely."  With such a rushed discussion, this never made it in yesterday, but truth be told I would have dismissed the possibility as remote, anyway.  That said, the reason for any concern at all was the channeled nature of the vorticity.  Experience has shown that a fast moving and relatively channeled vort will only produce appreciable precipitation in bursts, or along the thin ribbon of PVA that precedes it.  That was the case in this event, which meant the resultant low level center was also very compact, and therefore moisture entrainment was limited.  An interesting question is: If we are going to give respect to the channeled nature of the vorticity, does that mean we should use the same caution for later this week?  The answer is probably yes.

In the short term, instability is combining with orographic lift and more importantly dynamic lift ahead of a shortwave straddling the Canada border Wed afternoon to create increasing convective snow showers along the Green and White Mountains.  These will continue until evening passage of the shortwave, then diminish.  Elsewhere, a quiet afternoon and evening - have gone with PC conditions overnight given diminishing low level clouds early but increasing middle and high altitude clouds later.  With warm and moist advection at almost all levels of the atmosphere, and into a cold antecedent airmass, on Thursday, I'm expecting plenty of clouds at many levels.  Some breaks of sun are likely to be found between these from time to time, but I don't think they will be the remembered feature of the day.  Additionally, with a gradual and widespread warm and moist advection, overall weak isentropic lift will aid in scattered snow showers as the lower atmosphere moistens later in the day and Thu eve.  Overnight Thu Ngt is when things turn a bit more interesting with the approach of the Srn stream shortwave.  The assoc sfc cyclone will have interacted with Gulf moisture, and this will be a juicy storm and, of course, the question is whether this moisture streams northward into NewEng.  To simply follow the QPF or RH fields of the models would be maddening over the course of the week, and instead we need to look at the synoptic pattern.  We know, of course, that a strong upper low remains near Hudson Bay with a large trough over the Eastern 2/3 of the United States.  The situation isn't just this simple, however.  Upstream we find very strong positive height anomalies associated with the Alaskan ridge - the same ridge we looked at together several weeks ago that would be building and sending deep cold our way.  Build it did, and today Alaska is sitting in what is record warmth at 850 mb, as the 850 mb temp soared to +8 C at Fairbanks when hurricane force winds blasted warmth deep into Alaska.  In addition to setting up Chinook winds in Alaska in January (wow), this also is a sign of just how amplified our weather pattern is, especially when one considers that Fairbanks was in the depths of tremendous cold just three to four weeks ago.

So what does all of this mean for us?  What it means is fast north to south flow around the east side of that Alaskan ridge, taking shortwaves and racing them from Western Canada to the Rockies and SW US quickly.  But the broad nature of the trough extends from the SW US all the way to the Eastern Seaboard, and with negative height anomalies even over the Central Atlantic, it's very hard to turn anything significantly northward.  In fact, if we were to forecast only by the 500 mb flow and vort maxes, we'd wonder how to get more than just the northern shield of a storm into NewEng, thanks largely to the relatively flat and fast flow from the Southern Rockies to the Nrn Mid-Atlantic coastline.  In this fast flow with tight packing of isoheights, vorticity remains channeled, making it even more difficult to bring precip north.

This leaves us with a setup that brings enuf isentropic lift for at least light precip Thu Ngt, then by late Thu Ngt/early Fri the approach of the channeled vort should bring a period of slightly more significant precip, but does not extend very far northward and therefore will be difficult to pull much precip northwest.  This is likely a big reason of why we're witnessing a southern trend in the guidance, and while a southward suppression does look good for the bulk of the moisture, this channeled vort should still be able to provide enuf lift to extend the precip shield into Srn NewEng - esp Ern areas - and I've held onto the potential for a few inches of snow in parts of Srn NewEng.  Given the longwave pattern, however, I'm unable to bite on more than that at this point.

By Fri afternoon this first shot is likely gone as the storm remains progressive until slowing and bombing in Ern Canada, but another vort max will zip east from the Great Lakes Fri ngt and may bring another round of snow showers.  In fact, the vorticity advection is actually better with the Fri ngt shortwave than it is Thu ngt into Fri!  This serves as a reminder that we are, to some extent, making a mountain out of a molehill with the Thu Ngt/Fri event, giving credence to the moisture availability just south of us but having trouble acknowledging that there just aren't enough favorable dynamics over NewEng to make it work.

The combo of the Fri ngt vort max and the strengthening storm in Ern Canada will bring a steady wind and a steady flow of colder air into NewEng on Sat, though the more impressive arctic chill will lurk behind an arctic front that will be stationary north of NY and on the move east across the Great Lakes.  This front should move thru with another vort Sat ngt, and will usher in colder air for Sun.

Another burst of deep cold appears en route for next Tue...but the question is whether we have anything hidden in the details to contend with as that arctic air works south.  The longwave pattern appears favorable Sunday night for a wave to develop along or just ahead of the southward surge of arctic air, and this has peaked my interest for Sunday night/Monday.  Right now, there's limited support from guidance, but the combination of a trof axis to our west, a shortwave rotating around the base of the trof, and the arctic front pressing south marks it as an alert for the synoptic pattern before the cold comes on strong for the middle of next week.

Have a great Wednesday.

Matt

Tuesday's Discussion:

1:10 PM:  Literally on my way out the door for an appearance but wanted to get a few thoughts down.  For tonight's event, the great satellite presentation speaks for itself as buzzsaw vort max spins east and has great signature - even a super radar presentation right at the center of the vortex for a time this morning.  Amazing!  There should be no doubt of the integrity of this circulation as it moves east, and I'm quite comfortable with it developing healthy bands of snow.  Ratios should be just under 20:1 on average with omega on the cold end of the dendritic crystal growth spectrum, tho cold thru the lower atmosphere, too, which reduces potential for aggregation, thereby cutting back on ratios from what they could be, which would have been even higher.  I like the NMM representation given weak to moderate frontogenic forcing that should keep a rather contiguous west to east band of precip out of Upstate NY and across NewEng.  Amounts will obviously be increased as Atlantic moisture is finally tapped by this vortex - it's already shown response to Great Lake moisture today.  850-500 mb lapse rates are strong and steep late tonight, tho this passes over most of Ern MA just prior to a llvl easterly flow developing.  Over Cape Cod, the two come dangerously close to being in the same place at the same time which would mean a burst of heavy convective snows early tomorrow morning.  Have adlibbed a 6" CHH or ACK, but concern is there for all of SE MA if this instabillity is tapped sooner.  System will be progressive, but worth noting that in-house mesoscale model is really harping on mesolow development on north end of inverted trof along coast of ME - a Norlun feature of sorts.  I can find no additional support for that feature at this time and have not included it in the forecast, but you can bet I'll be glued to sat and radar for any signature first thing in the morning.  Otherwise, progressive nature brings breaks in clouds by mid-morning most spots.  I know the models have been trending south on the Thu Ngt/Fri storm in 12Z runs - I also know I wanted to have more time to look at that storm today and that's not going to happen except to say that I would NOT flip and flop with the models on this one.  Yes, the southward trend should be somewhat correct given the history of carrying storms to our south, but Southern New England still looks like a good bet at getting into some of this snow shield.

Matt

Monday's Discussion:

1:30 PM:  Cape Cod squalls began as Eastern MA snow showers along trof - showing some weak evidence of Norlun characteristics earlier today with instabililty above trof, though losing those characteristics now - and primary mechanism now appears to be ocean enhancement.  Most accumulation is done with this band after some localized rates around Chatham approaching 1"/hr early Mon AM.  Drier air evidenced across remainder of NewEng is coupling with downsloping flow for decent sun.

Though I don't expect all clouds to dissipate Monday night with one vort max pivoting across the Canadian border and another sliding east-northeast out of Upstate NY.  Ci deck likely to come in ahead of latter vort from midnight onward, though at the sfc winds will slacken.  NMM coming on board in its 12Z run with the outlier 00Z WRF solution of blossoming precip field last-minute over far Srn NewEng Tue eve and overnight Tue ngt.  It truly is a remarkable and challenging pattern we remain in, as frequent vort maxes need only moisture to thrive, but have by and large been devoid of that moisture, as is the case with today's impressive looking storm that sails southeast of NewEng and into the Canadian Maritimes.  This certainly can leave one feeling gunshy, which is probably a very good idea in the medium range period, though in the short range the details become a bit easier to distinguish.  This was the case with the Sun Ngt/Mon disturbance - appearing to have decent potential on Fri AM, but quickly becoming apparent it would be of little sensible consequence by Sat's guidance products.  In this case - for Tue ngt's disturbance - the setup is one that actually is favorable for "surprise" snow in Southern NewEng, though I suppose that's a bit of a misnomer for me to use considering we're examining the potential together here.  Nonetheless, we have a southern stream disturbance that, by itself, would sail south of NewEng once again.  The delicate twist here is a very weak northern stream disturbance riding parallel and coming E out of NY State by Tue eve that will provide dynamic lift over Southern NewEng, and looks as though it will induce just enough sfc cyclogenesis to develop good boundary layer positive theta-e advection Tue eve into Tue ngt.  Farther aloft there is less indication of this cyclone, but with an ocean sitting to our south and east, all we really need to do is get some sort of a south or east component around even a weak center to pull in enuf moisture to interact with the expanding dynamic lift.  These were the reasons I kept a chance of snow in for Tue Ngt in the AM forecast today, tho it's interesting to see that the NMM/GFS/GGEM/RGEM/WRF are all now on-board with measurable precip for the time period.  This is truly, yet again, another very delicate scenario as just a bit less development jeopardizes the moisture influx in the boundary layer, but for now it's certainly trending in a more moist - and therefore whiter - direction.  Total accums would likely not be significant, but in a snow-starved winter, even a few inches can go a long way.

Later down the line, another vort slides thru Thu Ngt, and then another Fri Ngt, it would appear, and either of these hold potential, with the latter of more interest.  Perhaps we will delve into this tomorrow or Wednesday.  For today, I'm out of time.

Matt

THOUGH A SLIGHT EVENT FOR MANY, TUESDAY NIGHT SNOW TO BE APPRECIABLE FOR SOME...TOUGH SOUTHERN NEW ENGLAND WEDNESDAY MORNING...ANOTHER STORM THURSDAY NIGHT & FRIDAY

Welcome to the weather blog - a regular Monday through Friday discussion of the weather!  While the discussions usually will only come on days I'm working, I'll issue special updates when the weather warrants.  I will always post to let you know when no discussion is expected if I'm away on vacation, etc. - if no update is here and no info is available, that likely means the server has temporarily gone on the fritz and I will update as soon as technically possible.  You'll find a quick weather synopsis linked to the daily forecast at the top of the page, a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow by mid-afternoon. My email is contact@mattnoyes.net.  This blog is for you, so I hope you enjoy it!  -Matt Noyes

General Weather Summary:

12:40 PM Update:  Have updated the accumulation map (below) just a touch.  Minor changes from the previous version, mainly to bump up amounts ever so slightly in Northern Rhode Island hills and higher terrain of interior Southern MA.

Previous Discussion:  The migration of arctic air has been intriguing to watch over the past couple of weeks, and will have an impact on our weather for weeks to come.  For the first half of the winter, New England was exposed to cold air only in quick bursts - northwest wind carrying cold southward from Quebec and Ontario.  But this cold air was well-established in Canada and now, after a period of a few weeks of repetitive cold, the source of cold air has settled south into Northern New England, where deep cold will remain present for the next couple of weeks, and will ensure that plenty of cold air is available for the remainder of New England, as well, which would serve important when more moisture becomes involved in our weather pattern.

For some time now, the very same weather pattern that's been frustrating New England snow lovers has also been responsible for churning our seas for mariners.  That is, our prevailing jet stream pattern continues to deliver air that's just cold enough, and much more importantly, just dry enough to keep deep moisture to our south.  This has meant one storm after the next passing south of New Englnad, with the counterclockwise flow of wind around each storm center hurling ocean swell coastward, while prevailing offshore winds closer to New England add chop.  This has meant several ocean storms - and very few coastal storms - over the past few weeks.  In the immediate future, there's no evidence this will change, though the next few weeks will bring a gradual shift toward a pattern favoring higher frequency of storms.  Nonetheless, we're on the doorstep of a storm with potential for some of us slated for Tuesday night into Wednesday morning, while for others the upcoming event will be only a very light or even completely negligible event. 

Daybreak Tuesday brought quiet and cold conditions, with some spots in Northern New England recording their coldest morning in the last few days.  Though skies dawned mostly clear - with a few flurries found only in the Berkshires where westerly surface winds were pushing up against the mountainfaces - clouds were evident to our southwest on satellite imagery.  These clouds are the outer effects of a slow-moving and weak storm crawling east out of the Great Lakes that will continue to spread thickening clouds over New England through the day on Tuesday from southwest to northeast.  For those of you who are weather fanatics, I'd urge you to take a look at the satellite imagery linked to the left of this discussion, or the Northeast radar composite linked just above the local radars at right.  What you'd find is a well-defined spiral in the atmosphere...pinwheeling bands of clouds and associated snow showers with heavier squalls that have been making the trip steadily east from Michigan to Pennsylvania and New York.  These squalls have, at least in spots, been quite impressive given the lack of moisture with the approaching system.  Instead, the snow bands are driven by ample energy aloft - evidenced by the swirling pattern of the clouds - and this alone has been sufficient to bring near white-out conditions to some parts of the Upper Ohio Valley!  This is rather impressive for a moisture-starved system, and is nature's key that plenty of potential exists with this disturbance.

Ahead of the energy center, clouds will gradually increase and thicken over New England later Tuesday.  In the mountains of Northern and Western New England, a few flurries are likely from time to time Tuesday afternoon, with scattered snow showers a better bet across Central and Western New England by Tuesday evening.  Even still, there will continue to be a separation between energy and moisture - with energy diving in from the west and north, and deep moisture locked south of New England.  For most of us, this will mean a period of snow that will blossom as it migrates eastward, squeezing out only an inch or two in the western half of Southern and parts of Central New England, but increasing in intensity as it reaches eastern areas.  The reason for this intensification comes thanks to so much energy aloft, which aids in developing a closed center of circulation in the lowest several thousand feet of the atmosphere.  A developing storm turns counter-clockwise, and this will result in a weak south and even easterly flow tugging Atlantic moisture into the coastline, providing the missing ingredient for this energy center to thrive.  It makes sense, therefore, that areas closest to the moisture will see the greatest snowfall, and this appears to be on Cape Cod.  One factor that will cut down on accumulations is the progressive nature of the storm, which will carry most of the snow offshore by mid-morning.  Nonetheless, with snow expected to still be falling early Wednesday morning in Eastern Massachusetts, and fresh snow elsewhere, Wednesday morning's commute is likely to start out somewhat difficult.

Later Wednesday, as the storm pulls quickly away from New England, a few snow showers are likely to linger in the mountains while the remainder of New England finds breaks of sun and breezy, cool conditions.  This break in the action will last into Thursday, before another disturbance moves toward New England Thursday night.  Contrary to its predecessors, this storm will have plenty of moisture thanks to a track that will bring the storm near the Gulf of Mexico coastline before it prepares to wrap northward and redevelops off the Atlantic Seaboard.  The most likely scenario is for snow to overspread New England Thursday night well in advance of the main storm center, then become heavier heading into Friday.  At this point - given ocean water temperatures still running in the 40s in the open ocean south and east of New England - it's likely that at least some warm air will be carried northward with this storm that may result in a mix with and perhaps change to rain in far southeastern New England on Friday.  I'm not sold on this warmth penetrating too far north, though, largely because of what I discussed at the start of this discussion, which is the cold airmass well in place across Northern New England.  This is not only cold but also quite dense and stubborn and will not budge even with approach of warmth from the south.  The result will likely be for easterly winds to become more northeasterly Thursday night into Friday, resulting in a very slow northward progression of any rain/snow line.  Therefore, the potential exists for significant accumulation through much of New England Thursday night through Friday and this is a storm worth paying close attention to.

In the longer range, the second and third weeks of February will bring a shift in the pattern that will result in shrinking the overall coverage of deep cold over the Lower 48, but will also help to nudge the axis of coldest air west just a bit, over the Great Lakes and Ohio Valley, which would allow moisture to stream northward over the Eastern Seaboard.  In essence, this should theoretically allow for the storms that have been blasting off just off the coastline the past few weeks to begin taking off near or over the coastline as we round the corner into February.  This is something worth watching.

For what it's worth, I was skiing this weekend in New Hampshire and the conditions were fantastic, and reports from ALL New England states are just as stellar.  Anyone considering not skiing because of fear of conditions is worried for no reason - the man-made conditions are amazing and worth the trip.  No, I'm not being paid by the ski areas to say it - just a long-time New England skier who loves to share the news!

Enjoy a bit of snow!

Matt

Matt's Technical Meteorological Discussion: Updated Tuesday, January 30 at 1:10 PM

Literally on my way out the door for an appearance but wanted to get a few thoughts down.  For tonight's event, the great satellite presentation speaks for itself as buzzsaw vort max spins east and has great signature - even a super radar presentation right at the center of the vortex for a time this morning.  Amazing!  There should be no doubt of the integrity of this circulation as it moves east, and I'm quite comfortable with it developing healthy bands of snow.  Ratios should be just under 20:1 on average with omega on the cold end of the dendritic crystal growth spectrum, tho cold thru the lower atmosphere, too, which reduces potential for aggregation, thereby cutting back on ratios from what they could be, which would have been even higher.  I like the NMM representation given weak to moderate frontogenic forcing that should keep a rather contiguous west to east band of precip out of Upstate NY and across NewEng.  Amounts will obviously be increased as Atlantic moisture is finally tapped by this vortex - it's already shown response to Great Lake moisture today.  850-500 mb lapse rates are strong and steep late tonight, tho this passes over most of Ern MA just prior to a llvl easterly flow developing.  Over Cape Cod, the two come dangerously close to being in the same place at the same time which would mean a burst of heavy convective snows early tomorrow morning.  Have adlibbed a 6" CHH or ACK, but concern is there for all of SE MA if this instabillity is tapped sooner.  System will be progressive, but worth noting that in-house mesoscale model is really harping on mesolow development on north end of inverted trof along coast of ME - a Norlun feature of sorts.  I can find no additional support for that feature at this time and have not included it in the forecast, but you can bet I'll be glued to sat and radar for any signature first thing in the morning.  Otherwise, progressive nature brings breaks in clouds by mid-morning most spots.  I know the models have been trending south on the Thu Ngt/Fri storm in 12Z runs - I also know I wanted to have more time to look at that storm today and that's not going to happen except to say that I would NOT flip and flop with the models on this one.  Yes, the southward trend should be somewhat correct given the history of carrying storms to our south, but Southern New England still looks like a good bet at getting into some of this snow shield.

Matt

Monday's Discussion:

1:30 PM:  Cape Cod squalls began as Eastern MA snow showers along trof - showing some weak evidence of Norlun characteristics earlier today with instabililty above trof, though losing those characteristics now - and primary mechanism now appears to be ocean enhancement.  Most accumulation is done with this band after some localized rates around Chatham approaching 1"/hr early Mon AM.  Drier air evidenced across remainder of NewEng is coupling with downsloping flow for decent sun.

Though I don't expect all clouds to dissipate Monday night with one vort max pivoting across the Canadian border and another sliding east-northeast out of Upstate NY.  Ci deck likely to come in ahead of latter vort from midnight onward, though at the sfc winds will slacken.  NMM coming on board in its 12Z run with the outlier 00Z WRF solution of blossoming precip field last-minute over far Srn NewEng Tue eve and overnight Tue ngt.  It truly is a remarkable and challenging pattern we remain in, as frequent vort maxes need only moisture to thrive, but have by and large been devoid of that moisture, as is the case with today's impressive looking storm that sails southeast of NewEng and into the Canadian Maritimes.  This certainly can leave one feeling gunshy, which is probably a very good idea in the medium range period, though in the short range the details become a bit easier to distinguish.  This was the case with the Sun Ngt/Mon disturbance - appearing to have decent potential on Fri AM, but quickly becoming apparent it would be of little sensible consequence by Sat's guidance products.  In this case - for Tue ngt's disturbance - the setup is one that actually is favorable for "surprise" snow in Southern NewEng, though I suppose that's a bit of a misnomer for me to use considering we're examining the potential together here.  Nonetheless, we have a southern stream disturbance that, by itself, would sail south of NewEng once again.  The delicate twist here is a very weak northern stream disturbance riding parallel and coming E out of NY State by Tue eve that will provide dynamic lift over Southern NewEng, and looks as though it will induce just enough sfc cyclogenesis to develop good boundary layer positive theta-e advection Tue eve into Tue ngt.  Farther aloft there is less indication of this cyclone, but with an ocean sitting to our south and east, all we really need to do is get some sort of a south or east component around even a weak center to pull in enuf moisture to interact with the expanding dynamic lift.  These were the reasons I kept a chance of snow in for Tue Ngt in the AM forecast today, tho it's interesting to see that the NMM/GFS/GGEM/RGEM/WRF are all now on-board with measurable precip for the time period.  This is truly, yet again, another very delicate scenario as just a bit less development jeopardizes the moisture influx in the boundary layer, but for now it's certainly trending in a more moist - and therefore whiter - direction.  Total accums would likely not be significant, but in a snow-starved winter, even a few inches can go a long way.

Later down the line, another vort slides thru Thu Ngt, and then another Fri Ngt, it would appear, and either of these hold potential, with the latter of more interest.  Perhaps we will delve into this tomorrow or Wednesday.  For today, I'm out of time.

Matt

ARCTIC AIR HOLDS FIRM ACROSS NORTH COUNTRY...WEATHER REMAINS TRICKY, BUT QUIET...GREAT SKIING CONTINUES!

Welcome to the weather blog - a regular Monday through Friday discussion of the weather!  While the discussions usually will only come on days I'm working, I'll issue special updates when the weather warrants.  I will always post to let you know when no discussion is expected if I'm away on vacation, etc. - if no update is here and no info is available, that likely means the server has temporarily gone on the fritz and I will update as soon as technically possible.  You'll find a quick weather synopsis linked to the daily forecast at the top of the page, a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow by mid-afternoon. My email is contact@mattnoyes.net.  This blog is for you, so I hope you enjoy it!  -Matt Noyes

General Weather Summary:

The migration of arctic air has been intriguing to watch over the past couple of weeks, and will have an impact on our weather for weeks to come.  For the first half of the winter, New England was exposed to cold air only in quick bursts - northwest wind carrying cold southward from Quebec and Ontario.  But this cold air was well-established in Canada and now, after a period of a few weeks of repetitive cold, the source of cold air has settled south into Northern New England, where deep cold will remain present for the next couple of weeks, and will ensure that plenty of cold air is available for the remainder of New England, as well, which would serve important when more moisture becomes involved in our weather pattern.

For the timebeing, yet another storm is cranking up just southeast of New England on Monday, and yet another storm has dealt a "close but no cigar" shave to New Englanders.  The satellite presentation of this storm is very impressive as it cranks up over open waters, but it is progressive and will continue to scream northeast into the Canadian Maritimes.  Left behind has been a very weak trough - showing some characteristics of the "Norlun Trough" I discussed in length last week - draped over Cape Cod.  In short, this is a weak disturbance that represents a shift in wind direction, and can serve to focus moisture into very localized squalls.  This has been the case over Cape Cod Monday morning, with some ocean enhancement as cold air streams across relatively warm ocean waters, bringing bursts of 1" per hour snows Monday morning to the Outer Cape, and resulting in a few fluffy inches from Hyannis to Provincetown!  As the developing ocean storm steams away and winds increase from the northwest, this weak Norlun Trough also will shift east, leaving increasing sunshine for even the Outer Cape by late Monday.  Elsewhere, sunshine has already been on the increase and will help to counteract the cold northwest winds that will keep temperatures below Sunday's noticeably milder readings.  With wind gusts to over 25 mph factored in, wind chill values will run close to 20 south, and close to 10 above zero north.

On the water, I want to take a moment to acknowledge that it was an apparently tragic weekend off the coast of Southern New England, when the New Bedford based fishing vessel "Lady of Grace" capsized in Nantucket Sound.  The boat was found at the bottom of a 36 foot deep area of the Sound, and tragically what is believed to have been the only life raft was still attached to the boat.  Whether this was a result of freezing spray or not will be determined by an ongoing investigation, but certainly this helps to outline the dangers of freezing spray for our dedicated New England fishermen and women who brave the conditions daily.  For those who are landlubbers and not aware of this phenomenon, freezing spray occurs when wave action causes ocean water to spray skyward, splashing onto boats and - due to very cold air - freezing on contact.  We also saw sea smoke this weekend - fog that develops above the warm ocean in bitter arctic air, and this, too, provides droplets of water that will freeze on surfaces.  The result can be caked ice on structures such as boats, and can serve to weigh a vessel down, making it top-heavy.  Today on the waters of New England, light freezing spray is still a possibility, but nothing near what was experienced in the windy arctic blast that began the weekend.  My thoughts are with the family and friends of the Lady of Grace crew, and I want the marine community to know that my support is always with you.

Part of what's been churning our seas so vigorously, and so relentlessly, has been the very same weather pattern that's been frustrating New England snow lovers.  That is, we've transitioned to a pattern that continues to deliver air that's just cold enough, and much more importantly, just dry enough to keep deep moisture to our south.  This has meant one storm after the next passing south of New Englnad, with the counterclockwise flow of wind around each storm center hurling ocean swell coastward, while prevailing offshore winds closer to New England add chop.  This has meant several ocean storms - and very few coastal storms - over the past few weeks.

In the immediate future, there's no evidence this will change, though the next few weeks will bring a gradual shift toward a pattern favoring higher frequency of storms.  For now, the chilly and dry blast of air on Monday will continue the trend of emerging sunshine, eventually even reaching the freshly snow-blanketed Outer Cape.  With temperatures in the 20s south and teens north, and winds sustained from the northwest at 15-25 mph, wind chill values will drop to around 20 south and around 10 north.  Expect a relatively quiet night Monday night as New England sits between weather systems.

Tuesday will dawn quiet and cold, though a slow-moving and weak storm crawling east out of the Great Lakes will eventually spread increasing clouds over New England later Tuesday.  In the mountains of Northern and Western New England, a few flurries are likely from time to time Tuesday afternoon, with scattered snow showers a better bet across New England Tuesday night.  Even still, there will continue to be a separation between energy and moisture - with energy diving in from the west and north, and deep moisture locked south of New England.  There are signs the two will interact just in time to bring enhanced snow showers to the South Coast late Tuesday night into early Wednesday, though given the recent pattern, there's reason to doubt how much that really will amount to.  Nonetheless, communities hit with overnight snow showers will find enough snow coating to make roads slick in a few spots.

By Wednesday, any early snow showers will give way to another break in the action and another brief shot of cool air that will last into Thursday, though not nearly as cold as this past weekend's arctic blast that kept temperatures in the teens.  Our next chance of snow would come Thursday night into Friday with yet another disturbance racing across New England, and at this point it's still somewhat uncertain as to just how quickly this disturbance would develop, and once again it looks like most of the action would remain south of New England.

Of more potential is the following disturbance, slated for later Friday into Saturday.  There are a few strong signatures with this setup - including a strong available energetic disturbance and indications of a new strong surge of cold behind the storm, indicating a strengthening circulation - but we've seen a few favorable setups for storms at four and five days out already this year that have failed to materialize to more than light and in a few cases locally moderate snowfalls, so I have to admit that from five days out I'm hesitant to jump all over this potential, but will continue to watch it.

What I can tell you is that the second and third weeks of February will bring a shift in the pattern that will result in shrinking the overall coverage of deep cold over the Lower 48, but will also help to nudge the axis of coldest air west just a bit, over the Great Lakes and Ohio Valley, which would allow moisture to stream northward over the Eastern Seaboard.  In essence, this should theoretically allow for the storms that have been blasting off just off the coastline the past few weeks to begin taking off near or over the coastline as we round the corner into February.  This is something worth watching.

For what it's worth, I was skiing this weekend in New Hampshire and the conditions were fantastic, and reports from ALL New England states are just as stellar.  Anyone considering not skiing because of fear of conditions is worried for no reason - the man-made conditions are amazing and worth the trip.  No, I'm not being paid by the ski areas to say it - just a long-time New England skier who loves to share the news!

Have a great start to your week.

Matt

Matt's Technical Meteorological Discussion: Updated Monday, January 29 at 1:30 PM

Cape Cod squalls began as Eastern MA snow showers along trof - showing some weak evidence of Norlun characteristics earlier today with instabililty above trof, though losing those characteristics now - and primary mechanism now appears to be ocean enhancement.  Most accumulation is done with this band after some localized rates around Chatham approaching 1"/hr early Mon AM.  Drier air evidenced across remainder of NewEng is coupling with downsloping flow for decent sun.

Though I don't expect all clouds to dissipate Monday night with one vort max pivoting across the Canadian border and another sliding east-northeast out of Upstate NY.  Ci deck likely to come in ahead of latter vort from midnight onward, though at the sfc winds will slacken.  NMM coming on board in its 12Z run with the outlier 00Z WRF solution of blossoming precip field last-minute over far Srn NewEng Tue eve and overnight Tue ngt.  It truly is a remarkable and challenging pattern we remain in, as frequent vort maxes need only moisture to thrive, but have by and large been devoid of that moisture, as is the case with today's impressive looking storm that sails southeast of NewEng and into the Canadian Maritimes.  This certainly can leave one feeling gunshy, which is probably a very good idea in the medium range period, though in the short range the details become a bit easier to distinguish.  This was the case with the Sun Ngt/Mon disturbance - appearing to have decent potential on Fri AM, but quickly becoming apparent it would be of little sensible consequence by Sat's guidance products.  In this case - for Tue ngt's disturbance - the setup is one that actually is favorable for "surprise" snow in Southern NewEng, though I suppose that's a bit of a misnomer for me to use considering we're examining the potential together here.  Nonetheless, we have a southern stream disturbance that, by itself, would sail south of NewEng once again.  The delicate twist here is a very weak northern stream disturbance riding parallel and coming E out of NY State by Tue eve that will provide dynamic lift over Southern NewEng, and looks as though it will induce just enough sfc cyclogenesis to develop good boundary layer positive theta-e advection Tue eve into Tue ngt.  Farther aloft there is less indication of this cyclone, but with an ocean sitting to our south and east, all we really need to do is get some sort of a south or east component around even a weak center to pull in enuf moisture to interact with the expanding dynamic lift.  These were the reasons I kept a chance of snow in for Tue Ngt in the AM forecast today, tho it's interesting to see that the NMM/GFS/GGEM/RGEM/WRF are all now on-board with measurable precip for the time period.  This is truly, yet again, another very delicate scenario as just a bit less development jeopardizes the moisture influx in the boundary layer, but for now it's certainly trending in a more moist - and therefore whiter - direction.  Total accums would likely not be significant, but in a snow-starved winter, even a few inches can go a long way.

Later down the line, another vort slides thru Thu Ngt, and then another Fri Ngt, it would appear, and either of these hold potential, with the latter of more interest.  Perhaps we will delve into this tomorrow or Wednesday.  For today, I'm out of time.

Matt

INTENSE SHOT OF COLD PULLS AWAY AND LEAVES MILDER WINTER WEEKEND...SNOW SATURDAY AND SNOW SUNDAY NIGHT ARE NEXT FOCUS FOR NEW ENGLAND

Welcome to the weather blog - a regular Monday through Friday discussion of the weather!  While the discussions usually will only come on days I'm working, I'll issue special updates when the weather warrants.  I will always post to let you know when no discussion is expected if I'm away on vacation, etc. - if no update is here and no info is available, that likely means the server has temporarily gone on the fritz and I will update as soon as technically possible.  You'll find a quick weather synopsis linked to the daily forecast at the top of the page, a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow by mid-afternoon. My email is contact@mattnoyes.net.  This blog is for you, so I hope you enjoy it!  -Matt Noyes

General Weather Summary:

The intense shot of arctic cold in New England on Friday will be short-lived, leaving what should be a fantastic weekend for skiing across New England, though some spots will see enough snow to slicken roadways for a time Saturday, and another chance of snow returns on Sunday.

The largescale weather pattern remains virtually unchanged - that is, the presence of a jet stream trough - a dip in the jet stream winds aloft - over the Northeastern United States and Southeastern Canada.  Keep in mind that the jet stream is the fast corridor of wind aloft that steers storm systems and acts as a thermostat, separating cold air to the north from warmer air to the south.  With a dip in these winds, New England remains squarely on the cold side of the thermostat, and there we'll stay for awhile to come.  The result of this deep trough has been to keep storms strengthening just southeast of New England, one after the next, then keep strong storms spinning east of our area.  The latest of these powerful storms backed westward far enough to increase winds across the six-state region Thursday night into Friday, but as that storm weakens and shifts away from us, so too, go the bitter winds.

In the meantime, the dangerous combination of cold and wind provided brutal conditions for people and animals alike who had to brave the 30 mph wind gusts and resultant wind chills to as low as 40 below zero Thursday night.  Early Friday morning dawned with widespread temperatures below zero in Central and Northern New England, and into the single digits even for the major metropolitan areas of Southern New England.  The coldest temperature report I've found thus far in New England was Big Black River, Maine, checking in with an astounding 28 degrees below zero early Friday morning!  Even at the mildest time of day on Friday, actual high temperatures will range from near zero north to the teens south, and wind chills will remain below zero for nearly all of us.  Incidentally, it's probably worth pointing out that wind chill has no bearing on actual temperature - most weather-savvy folks know this but for those who dabble in the weather, it's important to point out.  Around our bodies - and, in fact, around all objects - is a laminar layer of air...that is, a very thin layer of air that traps warmth...can be found.  Normally, this laminar layer acts like an envelope of warmth to protect our bodies from surrounding cold air, but when the wind blows, this thin layer of warmth is blown away, which exposes skin to the effects of cold temperatures much quicker than normal.  The result can be frostbite in as little as one or two minutes for exposed skin on days like today!  While each individual is different - and therefore our skin responds differently - this can be a concern for many.

Early Friday "bay effect" snow showers on the elbow of the Cape dropped a quick and fluffy accumulation, and after shifting offshore, a new weak band of snow showers may redevelop for the Upper Outer Cape later Friday, though of less significance.  Snow showers have also been falling south of Lake Champlain, where bitter cold air blowing across the relatively warm lake waters has set up a lake effect snow event.  A couple of fluffy inches are possible south of the Lake.  Elsewhere, expect sunshine to mix with cold and billowing cumulus clouds for a few flurries and snow showers from time to time.

Somewhat milder air will gradually ride back into New England on Saturday and Sunday, but with an active flow of disturbances overhead as the jet stream winds aloft begin to move a bit quicker, each of these disturbances will interact with the increasing warmth and moisture to produce a few areas of light snow.  One of these periods of light snow is likely to occur with the passage of the first disturbance during the first part of Saturday.  Friday morning analysis shows this disturbance in surface observations, and in satellite and radar imagery, over the Central Great Lakes and producing a swath of generally light snow.  With the jet stream winds poised to carry this disturbance eastward, a partly cloudy - and perhaps briefly mainly clear - night Friday night will give way to increasing and thickening clouds late.  By 8 AM Saturday, expect snow showers to break out over Western New England, and expand eastward, encompassing most of New England by mid-morning.  This period of snow will continue through mid-afternoon, dropping a general coating to under an inch in Southern New England, around in inch in Central New England and most of New Hampshire, with amounts of three or four inches up the spine of the Green Mountains and perhaps a few two or three inch amounts in the White Mountains.  Less snow will fall in Maine, where most of Central and Eastern Maine will see hardly any snow at all.

The disturbance slated for Sunday looks to be slow enough to hold snow off until evening, so at this point I'm expecting sunshine for a time, then increasing clouds but milder temperatures that will reach the 30s across most of Southern New England, and 20s across the Northern half of the six-state region.  The snow expected for later Sunday through Sunday night comes with a moderate strength disturbance, and the increase in warmth and moisture ahead of it raises the stakes a bit for accumulation potential.  Therefore, this Friday morning forecasting viewpoint suggests a few inches are possible Sunday night, leaving a messy start for many areas Monday morning.  It's likely that through the day Monday we'd see most of the moisture progressive and shifting east, but with lingering snow showers for awhile and clouds sticking around for a good part of the day, temperatures would be chilly.  Northerly winds are likely to prevail through Tuesday, further ensuring a stretch of cold air.

Winter lovers should delight in the fact that we'll remain below to much below normal on average through the middle of February!  By the first week of February, the pattern features a narrower corridor of cold slightly farther west from the coastline, which transitions our precipitation pattern from one of potential for blockbuster events, but low probability of them actually coming together over New England, to a pattern more conducive of Northern and Southern stream phasing, which would make storm frequency higher along the Eastern Seaboard.  Will it verify?  Only time will tell.

Have a wonderful weekend.

Technical Discussion:  None today.

Matt

Matt's Technical Meteorological Discussion: Updated Wednesday, January 24 at 1:45 PM

Squalls today assoc with arctic front are delivering near zero visibility in stronger cells and dropping a quick couple of inches for some, which will continue to ice roads.  Large part of this intensity coming from increased llvl convergence owing to orography and as arctic front procedes SE and out of higher terrain, squalls will become less intense and more scattered in nature.  Even in Central and Southern New England, terrain will still play a role in where strongest cells are located, even if that means the difference between existent and non-existent.  Winds gust ahead of and behind front, tho not impressively.  Tho there is a strong wind event ahead, it's not a result of this front.

Instead, the upcoming wx will be strongly dominated by the interaction between the digging trof and the retrograding low from Newfoundland.  Winds will diminish for a time tonight into early Thu, then pick up again as strong Ern Canada sfc low is drawn westward by southward sinking upper low.  The cold pool aloft is quite impressive with this upper level feature - to the tune of -40 C and colder at 500 mb - and this will mean very favorable conditions for convective clusters of snow on Thu across nearly all of New Eng.  Additionally, you'll remember the concerns for development of an arctic wave expressed earlier this week and centered on Thursday.  Though I don't expect a major event, it does look as though weak wave development will take place along the arctic frontal boundary on the south side of the upper level cold pool, and this will bring a period of steady though most likely light snow to far Southern NewEng - specifically southern CT, RI and SE MA Thursday late morning thru afternoon.  Accums should be light tho ratios will be very high, so any slight northward trend in the QPF field as already seen in 12Z runs would have major implications - even a tenth of an inch extra liquid could equate to 3 inches more snow in these areas.  I also want to stress that I'm very uncomfortable with this scenario and concerned implications will be greater than what they appear for the South Coast, and especially the Cape and Islands. After issuing this techie discussion, I'll be beefing up the wording in the forecast and General Wx Summary because of the northward trend in guidance, but much more importantly, the delicate and critical setup synoptically.  As for the RH and QPF fields, true that there isn't a whole lot to write home about in the operational guidance, but keep in mind that in an arctic airmass - and with an arctic wave - moisture doesn't need to be abundant to crank out accumulating fluffy high ratio snow.  The WRF is putting out up to .25 melted on ACK, and this would - if the ratios there resemble what they were in the remainder of NewEng yesterday - equate to over half a foot of snow on the island!  Though this is the most moist of the guidance, putting it into perspective with ratio certainly helps to drive home just how fine of a line we walk.  As for the synoptic situation I referenced, the vort sliding northeast over the waters just S of NewEng Thu  into Thu eve is elongated, but intense, and prompts widespread 500 mb UVM over Srn NewEng latter half of Thu.  This puts me on guard for a bit farther N progression of precip that most guidance would suggest, and keeps me very cautious that WRF may be onto something.  Additionally, this low should develop very quickly over the warm waters S and E of our South Coast, and probably will appear quite impressive.  We saw a storm quickly develop a baroclinic leaf on the south boundary of an arctic airmass with the last outbreak but it was well offshore.  This time, my concern is this happens closer to the Cape and Islands given the baroclinicity with warm ocean water and bitter cold air sfc and more importantly aloft, and while it probably still really takes off too late to nail anyone, even getting a northern fringe in its early ramp-up stage would bring a blanket of snow to far SE areas.

Farther north, I don't think we're out of the woods with conditions favorable for convective clusters, as mentioned above.  Meanwhile, the pressure gradient will tighten in response to the retrograding storm closing in on Northeastern NewEng, and this will kick winds back up later Thu through Thu night, meaning wind chill becomes more of a factor.  The continued cyclonic flow also dislodges the center of the cold air into NewEng - following its upper level polar vortex counterpart - and this will bring some of the coldest air available into Srn Quebec and Nrn NewEng, where high temps on Fri will end up below zero.  Prior to that, however, Thu night winds and cold will combine to bring chill factors to 40 below for most of the far North Country, and 20 below in even Southern NewEng!  Thu night also poses an interesting scenario weatherwise because it's the time during which the upper level low moves overhead, so I think it's wisest to keep squalls in the forecast in scattered form Thu ngt into Fri, which may affect the AM drive Fri, but given that we're working on uncertainties in the 24 hour window, would rather not get too fancy on this.

Weekend brings two vorts - one Sat AM that should be fairly light in nature for widespread light snow and departs by afternoon, then a more important one Sun AM that has more low level convergence to work with. The 500 mb pattern actually looks great for a progressive but quickly developing storm Sunday, so I'm not sure we should relax much on that wave, tho for now will not go hog wild on it given lack of good support from guidance.  Cold shot follows early next week.  More thoughts on the longer range tomorrow.

Matt

Tuesday's Discussion:

1:05 PM:  No time today before appearance.  Bottom line for techies is that we're tracking the meso low (impressive closed signature on sfc/buoy obs and gusts to 38 mph at PVC!) as it moves toward Central Maine coast late tonight and on Wednesday after brushing Cape with perhaps a few fluffy inches Wellfleet to P'town and less farther south, steered by 850 to sfc flow.  As it combines with warm advection on Wed, this should really light the snow up around Penobscot Bay where synoptic scale isentropic lift enhances lift already present thanks to convergence and instability.  Heaviest amounts of the event may result Wed in these areas.  Elsewhere, another fluffy coating - probably less than last night, tho still probably an impressive ratio. Ratios with last event were on the order of 30+ to 1, snow to water.

Matt

Monday's Discussions:

1:50 PM:  Update to the techie discussion (previous discussion below):  Wow.  Radar presentation of developing low off ME coast assoc with Norlun trof extremely impressive - feeder bands as of this writing are evident and sfc obs indicate a circulation that is trying to close.  If it succeeds in doing this, and continues to maintain improving presentation, the center of this meso low would have the potential to bring heavy snow if/where it makes "landfall" into the coast of ME.

1:45 PM:  Norlun trough event began earlier than I expected today across Srn ME coastline.  Passage of morning vort brought widespread snow showers dampened by dry boundary layer but left behind active Norlun trof.  Guidance has improved greatly on picking up on these events, but the concern is twofold today: 1) The amount of precipitation forecasted - expected to exceed .50" liquid equivalent, and 2) The location of these amounts, placed over the Gulf of Maine by operational guidance but verifying much farther inland in Northern York County thus far, and developing much sooner than anticipated.  Spoke with Kennebunk Police - many thanks for the info - who report snow has been moving farther inland through the day with large flakes accumulating at a steady rate.  This isn't surprising given that saturation has occurred in the dendritic crystal growth layer, which in concert with lingering arctic sfc airmass will create a quickly accumulating snow with a high ratio.  This is reason for concern, certainly, but is an event that truly is a humbling one for meteorologists.  Even though I saw the Norlun trough potential in advance, and see it developing a bit ahead of schedule now, the fact is that we're still largely at a loss as a field regarding where and when this band will drop its heaviest amounts.  At this point, given the overwhelming agreement among operational and SUNYSB MM5 guidance that the max precip stays over the waters, I'm going to continue to believe that.  Still, in today's noon show I issued an accumulation map with 3" amounts along the Maine coast from Nrn York County all the way to Knox County coast.  My reasoning for this was based upon the belief that this band will remain stationary for several hours - perhaps weakening with NVA before strengthening again in response to PVA ahead of shortwave currently moving east across Eastern Great Lakes - owing to very light wind fields in the lower levels, including 850 mb.  A west to southwest flow develops later Mon eve, and that's when I expect the band to shift east, though the area of enhanced snowfall rates is likely to expand thanks to increased dynamic lift, hence the reasoning for enhanced amounts all along the Maine coastline.  Inland by 10-15 miles, amounts will probably drop to around an inch.  Certainly there is some anxiety here, as a verification of heaviest amounts farther north would mean a tremendously higher amount of snow, while a due east shift of the Norlun trough would instead result in the higher amounts staying over water - eventually coming into line with guidance products - and hardly any more than a coating farther up the coastline.  So, I've tried to strike a conservative balance to alert folks adequately, yet not overreact, and have tried to emphasize the uncertain nature of this phenomenon in my broadcasts and in the General Wx Summary.  It does appear clear, however, that we'll be dealing with this Norlun trof in some way, shape and form through midweek!

Elsewhere, shortwave passage tonight will bring some weak interaction with moisture lifting north from main feed off Carolina coast.  This will produce widespread area of light snow, though amounts should total under an inch in just about all spots.  Again, some concern along outer Cape Ann and outer Cape Cod for enhancement due to Norlun trough, and have mentioned this in forecasts but not willing to bank on it yet given farther east development and slow eastward progression thus far.  Indications are that weak low pressure will develop along the Norlun trof Mon Ngt, and this would mean perhaps some weak ocean enhancement with easterly component in Eastern MA, where not only may highest amounts be observed, but also snow showers may linger into Tue AM.  Rest of Tue likely to bring some breaks of sun given midlvl drying, but high llvl RH combined with steadily cooling midlvl temps will create a pool of instability that will breed plenty of llvl clouds and snow showers, esp in orographically favored areas and where Norlun trof effects persist.

Warmest day of the week comes Wed in advance of powerful arctic front.  Good llvl WAA to boost temps but also will feed isentropic lift along Norlun trof, and is likely to enhance Central ME coastal snow on Wed as a result.  Arctic fropa occurs Wed afternoon and comes with decent llvl speed and directional convergence, which will bring favorable conditions for an active line of squalls in many areas.  An event like this is always a bit more tenuous in Eastern Srn NewEng, so would like to see a few more guidance runs before biting too hard, but see enuf with fcstd convergence, PVA, lift, ambient RH and airmass displacement to warrant putting them in the forecast.

Impressive surge of arctic air comes with wild retrogression of Newfoundland storm - as mentioned in General Wx Summary above, this is the same storm that's assoc with Mid-Atlantic moisture today.  Building ridge in Greenland forces storm to stall then retrograde as heights lower over Ern Canada behind it.  This mean a dump of cold and shortwaves into the trof, which is progged to sit directly over NewEng.  With so much energy, and such resultant baroclinicity sitting just S/SE of NewEng, I am so very hesitant to believe this will be a relatively quiet transition.  In fact, I don't believe that at all - there should be plenty of active weather through the period, and perhaps the greater question is whether we get a consolidated storm on the base of the trof Thu, over the waters south of NewEng for a coastal storm.  While operational models all suggest this will not be the case, a series of GFS Ensemble members do not want to let this potential go. I've kept snow in the forecast, because even if this situation does not produce an arctic wave - which is a real possibility - we should see convective squalls beneath the cold core on Thu, and yet another round of very strong wind and cold Thu that will last thru the end of the week.

Our next wave of low pressure would be likely Sat in response to a Nrn stream wave riding the thermal ribbon laid out across the Nrn Tier of the US.

Enjoy your day!

Matt

DANGEROUS COLD EN ROUTE THURSDAY NIGHT AND FRIDAY...GREAT SKIING WEEKEND IN STORE!

Welcome to the weather blog - a regular Monday through Friday discussion of the weather!  While the discussions usually will only come on days I'm working, I'll issue special updates when the weather warrants.  I will always post to let you know when no discussion is expected if I'm away on vacation, etc. - if no update is here and no info is available, that likely means the server has temporarily gone on the fritz and I will update as soon as technically possible.  You'll find a quick weather synopsis linked to the daily forecast at the top of the page, a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow by mid-afternoon. My email is contact@mattnoyes.net.  This blog is for you, so I hope you enjoy it!  -Matt Noyes

General Weather Summary:

Though the air is certainly plenty cold across New England on Thursday, the core of brutal arctic air will arrive Thursday night and take up residence through Friday.  This intense shot of Canada cold will be short-lived, leaving what should be a fantastic weekend for skiing across New England.

Our current weather pattern in the Northeast is defined by a jet stream trough - a dip in the jet stream winds aloft - over the Northeastern United States and Southeastern Canada.  Keep in mind that the jet stream is the fast corridor of wind aloft that steers storm systems and acts as a thermostat, separating cold air to the north from warmer air to the south.  With a dip in these winds, New England remains squarely on the cold side of the thermostat, and there we'll stay for awhile to come.  The result of this deep trough has been to keep strong storms spinning east of New England, and with a powerful storm backing westward through the Canadian maritimes and toward this trough, the counter-clockwise flow of wind around the storm will mean New England sees an increasing north and northwest wind.  As winds kick up from the north, cold air has been displaced from central and southern Canada, and has arrived to New England.

This air has brought a certain nip to the air on Thursday with temperatures not surpassing the lower 20s south and about 10 degrees north.  Though some sunshine will continue at times after starting the day in many locales, the presence of so much cold air and energy aloft - caught in the jet stream trough over New England - will mean lots of clouds bubbling up through the day with bursts of locally heavy snow at times, with just about all communities equally vulnerable.  Early morning squalls already brought slick conditions with numerous accidents on Interstate 95 in Southern Connecticut, and a similar situation will evolve through the day, taking on the look of a summertime thunderstorm day, when scattered activity hits some communities hard with quick accumulations and icing of roads, while others are spared.  Though the arctic cold front that brought the initial surge of wind and cold will be pressing farther south away from New England, the westward moving storm from Newfoundland mentioned earlier in this discussion will kick winds up again Thursday night, further enhancing the supply of arctic cold from Canada.  This cold air will combine with an increasing wind around the backside of the storm to send wind chill values plunging some 15 to 25 degrees below zero even in Southern New England, while Central and Northern New England will find wind chills as cold as 30 and 40 below zero, respectively - with actual temperatures 10 to 20 below zero north, 0 to 10 below central, and single digits south.  This kind of cold is dangerous cold - homeless shelters should expect a busy night, and folks with pets or animals outside should take severe cold weather precautions.  At the same time, energetic disturbances caught in the jet stream trough high above our heads will continue to promote snow showers and squalls scattered across New England Thursday night.  It also now appears as though the strengthening storm south of Cape Cod Thursday into Thursday evening mentioned yesterday will indeed strengthen just late enough, and just far enough south, to preclude any significant snow at the South Coast other than the aforementioned squalls.  A widespread frigid start Friday morning should help to kill any lingering weak car batteries before temperatures struggle to get out of the teens in our warmest locales and won't surpass zero in the north.

Somewhat milder air will gradually ride back into New England on Saturday and Sunday, but with an active flow of disturbances overhead as the jet stream winds aloft begin to move a bit quicker, each of these disturbances will interact with the increasing warmth and moisture to produce a few areas of light snow.  One of these periods of light snow is likely to occur with the passage of the first disturbance during the first part of Saturday.  The disturbance slated for Sunday looks to be a bit slower in latest guidance, so at this point I'm optimistic on daylight hours of Sunday bringing sunshine and milder temperatures, with thicker clouds and possible light snow more likely Sunday evening or night.  Between the light snow Saturday, moderating temperatures and lighter winds, all factors add up well for a great weekend of skiing in both Northern and Southern New Enlgand!

Behind these disturbances, another shot of bitter cold will come early next week, and winter lovers should delight in the fact that we'll remain below to much below normal on average through the middle of February!  By the first week of February, the pattern features a narrower corridor of cold slightly farther west from the coastline, which transitions our precipitation pattern from one of potential for blockbuster events, but low probability of them actually coming together over New England, to a pattern more conducive of Northern and Southern stream phasing, which would make storm frequency higher along the Eastern Seaboard.  Will it verify?  Only time will tell.

Enjoy your Thursday.

Technical Discussion:  None today.

Matt

Matt's Technical Meteorological Discussion: Updated Wednesday, January 24 at 1:45 PM

Squalls today assoc with arctic front are delivering near zero visibility in stronger cells and dropping a quick couple of inches for some, which will continue to ice roads.  Large part of this intensity coming from increased llvl convergence owing to orography and as arctic front procedes SE and out of higher terrain, squalls will become less intense and more scattered in nature.  Even in Central and Southern New England, terrain will still play a role in where strongest cells are located, even if that means the difference between existent and non-existent.  Winds gust ahead of and behind front, tho not impressively.  Tho there is a strong wind event ahead, it's not a result of this front.

Instead, the upcoming wx will be strongly dominated by the interaction between the digging trof and the retrograding low from Newfoundland.  Winds will diminish for a time tonight into early Thu, then pick up again as strong Ern Canada sfc low is drawn westward by southward sinking upper low.  The cold pool aloft is quite impressive with this upper level feature - to the tune of -40 C and colder at 500 mb - and this will mean very favorable conditions for convective clusters of snow on Thu across nearly all of New Eng.  Additionally, you'll remember the concerns for development of an arctic wave expressed earlier this week and centered on Thursday.  Though I don't expect a major event, it does look as though weak wave development will take place along the arctic frontal boundary on the south side of the upper level cold pool, and this will bring a period of steady though most likely light snow to far Southern NewEng - specifically southern CT, RI and SE MA Thursday late morning thru afternoon.  Accums should be light tho ratios will be very high, so any slight northward trend in the QPF field as already seen in 12Z runs would have major implications - even a tenth of an inch extra liquid could equate to 3 inches more snow in these areas.  I also want to stress that I'm very uncomfortable with this scenario and concerned implications will be greater than what they appear for the South Coast, and especially the Cape and Islands.  After issuing this techie discussion, I'll be beefing up the wording in the forecast and General Wx Summary because of the northward trend in guidance, but much more importantly, the delicate and critical setup synoptically.  As for the RH and QPF fields, true that there isn't a whole lot to write home about in the operational guidance, but keep in mind that in an arctic airmass - and with an arctic wave - moisture doesn't need to be abundant to crank out accumulating fluffy high ratio snow.  The WRF is putting out up to .25 melted on ACK, and this would - if the ratios there resemble what they were in the remainder of NewEng yesterday - equate to over half a foot of snow on the island!  Though this is the most moist of the guidance, putting it into perspective with ratio certainly helps to drive home just how fine of a line we walk.  As for the synoptic situation I referenced, the vort sliding northeast over the waters just S of NewEng Thu  into Thu eve is elongated, but intense, and prompts widespread 500 mb UVM over Srn NewEng latter half of Thu.  This puts me on guard for a bit farther N progression of precip that most guidance would suggest, and keeps me very cautious that WRF may be onto something.  Additionally, this low should develop very quickly over the warm waters S and E of our South Coast, and probably will appear quite impressive.  We saw a storm quickly develop a baroclinic leaf on the south boundary of an arctic airmass with the last outbreak but it was well offshore.  This time, my concern is this happens closer to the Cape and Islands given the baroclinicity with warm ocean water and bitter cold air sfc and more importantly aloft, and while it probably still really takes off too late to nail anyone, even getting a northern fringe in its early ramp-up stage would bring a blanket of snow to far SE areas.

Farther north, I don't think we're out of the woods with conditions favorable for convective clusters, as mentioned above.  Meanwhile, the pressure gradient will tighten in response to the retrograding storm closing in on Northeastern NewEng, and this will kick winds back up later Thu through Thu night, meaning wind chill becomes more of a factor.  The continued cyclonic flow also dislodges the center of the cold air into NewEng - following its upper level polar vortex counterpart - and this will bring some of the coldest air available into Srn Quebec and Nrn NewEng, where high temps on Fri will end up below zero.  Prior to that, however, Thu night winds and cold will combine to bring chill factors to 40 below for most of the far North Country, and 20 below in even Southern NewEng!  Thu night also poses an interesting scenario weatherwise because it's the time during which the upper level low moves overhead, so I think it's wisest to keep squalls in the forecast in scattered form Thu ngt into Fri, which may affect the AM drive Fri, but given that we're working on uncertainties in the 24 hour window, would rather not get too fancy on this.

Weekend brings two vorts - one Sat AM that should be fairly light in nature for widespread light snow and departs by afternoon, then a more important one Sun AM that has more low level convergence to work with.  The 500 mb pattern actually looks great for a progressive but quickly developing storm Sunday, so I'm not sure we should relax much on that wave, tho for now will not go hog wild on it given lack of good support from guidance.  Cold shot follows early next week.  More thoughts on the longer range tomorrow.

Matt

Tuesday's Discussion:

1:05 PM:  No time today before appearance.  Bottom line for techies is that we're tracking the meso low (impressive closed signature on sfc/buoy obs and gusts to 38 mph at PVC!) as it moves toward Central Maine coast late tonight and on Wednesday after brushing Cape with perhaps a few fluffy inches Wellfleet to P'town and less farther south, steered by 850 to sfc flow.  As it combines with warm advection on Wed, this should really light the snow up around Penobscot Bay where synoptic scale isentropic lift enhances lift already present thanks to convergence and instability.  Heaviest amounts of the event may result Wed in these areas.  Elsewhere, another fluffy coating - probably less than last night, tho still probably an impressive ratio.  Ratios with last event were on the order of 30+ to 1, snow to water.

Matt

Monday's Discussions:

1:50 PM:  Update to the techie discussion (previous discussion below):  Wow.  Radar presentation of developing low off ME coast assoc with Norlun trof extremely impressive - feeder bands as of this writing are evident and sfc obs indicate a circulation that is trying to close.  If it succeeds in doing this, and continues to maintain improving presentation, the center of this meso low would have the potential to bring heavy snow if/where it makes "landfall" into the coast of ME.

1:45 PM:  Norlun trough event began earlier than I expected today across Srn ME coastline.  Passage of morning vort brought widespread snow showers dampened by dry boundary layer but left behind active Norlun trof.  Guidance has improved greatly on picking up on these events, but the concern is twofold today: 1) The amount of precipitation forecasted - expected to exceed .50" liquid equivalent, and 2) The location of these amounts, placed over the Gulf of Maine by operational guidance but verifying much farther inland in Northern York County thus far, and developing much sooner than anticipated.  Spoke with Kennebunk Police - many thanks for the info - who report snow has been moving farther inland through the day with large flakes accumulating at a steady rate.  This isn't surprising given that saturation has occurred in the dendritic crystal growth layer, which in concert with lingering arctic sfc airmass will create a quickly accumulating snow with a high ratio.  This is reason for concern, certainly, but is an event that truly is a humbling one for meteorologists.  Even though I saw the Norlun trough potential in advance, and see it developing a bit ahead of schedule now, the fact is that we're still largely at a loss as a field regarding where and when this band will drop its heaviest amounts.  At this point, given the overwhelming agreement among operational and SUNYSB MM5 guidance that the max precip stays over the waters, I'm going to continue to believe that.  Still, in today's noon show I issued an accumulation map with 3" amounts along the Maine coast from Nrn York County all the way to Knox County coast.  My reasoning for this was based upon the belief that this band will remain stationary for several hours - perhaps weakening with NVA before strengthening again in response to PVA ahead of shortwave currently moving east across Eastern Great Lakes - owing to very light wind fields in the lower levels, including 850 mb.  A west to southwest flow develops later Mon eve, and that's when I expect the band to shift east, though the area of enhanced snowfall rates is likely to expand thanks to increased dynamic lift, hence the reasoning for enhanced amounts all along the Maine coastline.  Inland by 10-15 miles, amounts will probably drop to around an inch.  Certainly there is some anxiety here, as a verification of heaviest amounts farther north would mean a tremendously higher amount of snow, while a due east shift of the Norlun trough would instead result in the higher amounts staying over water - eventually coming into line with guidance products - and hardly any more than a coating farther up the coastline.  So, I've tried to strike a conservative balance to alert folks adequately, yet not overreact, and have tried to emphasize the uncertain nature of this phenomenon in my broadcasts and in the General Wx Summary.  It does appear clear, however, that we'll be dealing with this Norlun trof in some way, shape and form through midweek!

Elsewhere, shortwave passage tonight will bring some weak interaction with moisture lifting north from main feed off Carolina coast.  This will produce widespread area of light snow, though amounts should total under an inch in just about all spots.  Again, some concern along outer Cape Ann and outer Cape Cod for enhancement due to Norlun trough, and have mentioned this in forecasts but not willing to bank on it yet given farther east development and slow eastward progression thus far.  Indications are that weak low pressure will develop along the Norlun trof Mon Ngt, and this would mean perhaps some weak ocean enhancement with easterly component in Eastern MA, where not only may highest amounts be observed, but also snow showers may linger into Tue AM.  Rest of Tue likely to bring some breaks of sun given midlvl drying, but high llvl RH combined with steadily cooling midlvl temps will create a pool of instability that will breed plenty of llvl clouds and snow showers, esp in orographically favored areas and where Norlun trof effects persist.

Warmest day of the week comes Wed in advance of powerful arctic front.  Good llvl WAA to boost temps but also will feed isentropic lift along Norlun trof, and is likely to enhance Central ME coastal snow on Wed as a result.  Arctic fropa occurs Wed afternoon and comes with decent llvl speed and directional convergence, which will bring favorable conditions for an active line of squalls in many areas.  An event like this is always a bit more tenuous in Eastern Srn NewEng, so would like to see a few more guidance runs before biting too hard, but see enuf with fcstd convergence, PVA, lift, ambient RH and airmass displacement to warrant putting them in the forecast.

Impressive surge of arctic air comes with wild retrogression of Newfoundland storm - as mentioned in General Wx Summary above, this is the same storm that's assoc with Mid-Atlantic moisture today.  Building ridge in Greenland forces storm to stall then retrograde as heights lower over Ern Canada behind it.  This mean a dump of cold and shortwaves into the trof, which is progged to sit directly over NewEng.  With so much energy, and such resultant baroclinicity sitting just S/SE of NewEng, I am so very hesitant to believe this will be a relatively quiet transition.  In fact, I don't believe that at all - there should be plenty of active weather through the period, and perhaps the greater question is whether we get a consolidated storm on the base of the trof Thu, over the waters south of NewEng for a coastal storm.  While operational models all suggest this will not be the case, a series of GFS Ensemble members do not want to let this potential go.  I've kept snow in the forecast, because even if this situation does not produce an arctic wave - which is a real possibility - we should see convective squalls beneath the cold core on Thu, and yet another round of very strong wind and cold Thu that will last thru the end of the week.

Our next wave of low pressure would be likely Sat in response to a Nrn stream wave riding the thermal ribbon laid out across the Nrn Tier of the US.

Enjoy your day!

Matt

ARCTIC AIR BLASTS IN...FLAKES TO FLY IN SPOTS ON THURSDAY...WINTRY PATTERN TO PERSIST THROUGH MID-FEBRUARY, AT LEAST

Welcome to the weather blog - a regular Monday through Friday discussion of the weather!  While the discussions usually will only come on days I'm working, I'll issue special updates when the weather warrants.  I will always post to let you know when no discussion is expected if I'm away on vacation, etc. - if no update is here and no info is available, that likely means the server has temporarily gone on the fritz and I will update as soon as technically possible.  You'll find a quick weather synopsis linked to the daily forecast at the top of the page, a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow by mid-afternoon. My email is contact@mattnoyes.net.  This blog is for you, so I hope you enjoy it!  -Matt Noyes

General Weather Summary:

Snow squalls across some of New England on Wedneday herald in bitter arctic air that will rule over the Northeast for the next couple of days.  High in altitude, the active jet stream winds - the fast corridor of wind aloft that steers our storms and acts as a thermostat separating cold air to the north from warm to the south - will continue to dip over the Eastern United States, meaning cold air and energetic disturbances will continue to move overhead.

The past few days have brought varying results from these disturbances, but this is coming to a culmination, of sorts, Wednesday and Wednesday night.  As a storm strengthens over Newfoundland - the same storm that brought steady rains to the Carolinas earlier this week - new energy aloft is dropping out of Canada and into the jet stream "trough" - or dip - over the Northeast.  The result of this trough will actually be to pull the storm over Eastern Canada westward a bit, and the counter-clockwise flow of wind around the storm will mean New England sees an increasing north and northwest wind.  As winds kick up from the north, cold air has been displaced from central and southern Canada, and is en route to New England.  Led southeast by an arctic cold front, this new airmass will send temperatures plunging for all New Englanders by late Wednesday and Wednesday night.  The transition will be bumpy through the day Wednesday, with intense squalls at times along the high terrain of the Green Mountains and Berkshires, where at least a few inches will fall in most of the higher terrain, and several inches are likely in mountainous terrain of the Greens.  Farther east through the White Mountains and Mountains of Maine, scattered squalls will drop a quick inch or two of accumulation in some spots, making roads treacherous and reducing visibility to near zero at times.  Farther south and east, most of the remainder of New England will see sunshine giving way to building clouds with a few snow showers possible late Wednesday afternoon and Wednesday evening with the shift in wind from southwest to northwest associated with the passing arctic front.  These breezes will be somewhat active ahead of the front, but are more likely to gust to 30 mph just along and behind the front, and the drop in temperature will be apparent.  Downeast along the Maine coastline and inland through Washington County, the Norlun Trough we've looked at together in these discussions the past few days is diminishing, though has assisted in some enhanced snow showers in Eastern ME.  All New Englanders can monitor for snow showers and squalls through radar links at right.

Though winds will remain active and cold air will continue to pour southward Wednesday night - and this would favor continued snow showers in the mountains - the incoming arctic air will also be quite dry, and will probably favor partial clearing for most areas overnight as temperatures fall to around zero north, single digits central and teens south.  Active winds will knock about 10 to 15 degrees off actual temperatures with regard to "feels like" wind chill values.

Thursday will bring a biting chill to most of New England with an active breeze and temperatures not surpassing the lower 20s south and 10 degrees north.  Though some sunshine is possible to begin the day, the presence of so much cold air and energy aloft - caught in the jet stream trough over New England - will mean lots of clouds bubbling up through the day with bursts of locally heavy snow at times, with just about all communities equally vulnerable.  Though the arctic cold front that brought the initial surge of wind and cold will be pressing farther south away from New England, the westward moving storm from Newfoundland mentioned earlier in this discussion will kick winds up again Thursday night, further enhancing the supply of arctic cold from Canada.  This cold air will combine with an increasing wind around the backside of the storm to send wind chill values plunging some 15 to 25 degrees below zero even in parts of Southern New England, while Central and Northern New England will find wind chills as cold as 30 and 40 below zero, respectively.  At the same time, energetic disturbances caught in the jet stream trough high above our heads will continue to promote snow squalls scattered across New England - and perhaps converging into a more widespread area of snow - Thursday night.  It's rare to see such a cold and energetic system directly overhead, so the placement and intensity of these snow squalls is admitedly somewhat uncertain.  In fact, with a strong but elongated disturbance zipping over the waters south of New England on Thursday into Thursday evening, it's appearing increasingly likely that a band of steadier snow will establish from late morning onward across Connecticut, Rhode Island and Southeastern Massachusetts.  While this snow would not fall heavily for most areas, there is the potential that this storm will be strengthening quickly as it nears the Cape, and this may deliver more significant accumulations to the Cape and Islands later Thursday into Thursday night.  Otherwise, a widespread frigid start Friday morning should help to kill any lingering weak car batteries before temperatures struggle to get out of the teens in our warmest locales and won't surpass zero in the north.

Somewhat milder air will gradually ride back into New England on Saturday and Sunday, but with an active flow of disturbances overhead as the jet stream winds aloft begin to move a bit quicker, each of these disturbances will interact with the increasing warmth and moisture to produce a few areas of light snow.  One of these periods of light snow is likely to occur with the passage of the first disturbance during the first part of Saturday, before yet another may move from west to east across New England early Sunday.  These will probably provide at least a touch of fresh snow to lots of communities, and especially ski resorts where a round of freshies will make for two tremendous days on the slopes!

Behind these disturbances, another shot of bitter cold will come early next week, and winter lovers should delight in the fact that we'll remain below to much below normal on average through the middle of February!  By the first week of February, the pattern features a narrower corridor of cold slightly farther west from the coastline, which transitions our precipitation pattern from one of potential for blockbuster events, but low probability of them actually coming together over New England, to a pattern more conducive of Northern and Southern stream phasing, which would make storm frequency higher along the Eastern Seaboard.  Will it verify?  Only time will tell.

Have a wonderful day.

Matt

Matt's Technical Meteorological Discussion: Updated Wednesday, January 24 at 1:45 PM

Squalls today assoc with arctic front are delivering near zero visibility in stronger cells and dropping a quick couple of inches for some, which will continue to ice roads.  Large part of this intensity coming from increased llvl convergence owing to orography and as arctic front procedes SE and out of higher terrain, squalls will become less intense and more scattered in nature.  Even in Central and Southern New England, terrain will still play a role in where strongest cells are located, even if that means the difference between existent and non-existent.  Winds gust ahead of and behind front, tho not impressively.  Tho there is a strong wind event ahead, it's not a result of this front.

Instead, the upcoming wx will be strongly dominated by the interaction between the digging trof and the retrograding low from Newfoundland.  Winds will diminish for a time tonight into early Thu, then pick up again as strong Ern Canada sfc low is drawn westward by southward sinking upper low.  The cold pool aloft is quite impressive with this upper level feature - to the tune of -40 C and colder at 500 mb - and this will mean very favorable conditions for convective clusters of snow on Thu across nearly all of New Eng.  Additionally, you'll remember the concerns for development of an arctic wave expressed earlier this week and centered on Thursday.  Though I don't expect a major event, it does look as though weak wave development will take place along the arctic frontal boundary on the south side of the upper level cold pool, and this will bring a period of steady though most likely light snow to far Southern NewEng - specifically southern CT, RI and SE MA Thursday late morning thru afternoon.  Accums should be light tho ratios will be very high, so any slight northward trend in the QPF field as already seen in 12Z runs would have major implications - even a tenth of an inch extra liquid could equate to 3 inches more snow in these areas.  I also want to stress that I'm very uncomfortable with this scenario and concerned implications will be greater than what they appear for the South Coast, and especially the Cape and Islands.  After issuing this techie discussion, I'll be beefing up the wording in the forecast and General Wx Summary because of the northward trend in guidance, but much more importantly, the delicate and critical setup synoptically.  As for the RH and QPF fields, true that there isn't a whole lot to write home about in the operational guidance, but keep in mind that in an arctic airmass - and with an arctic wave - moisture doesn't need to be abundant to crank out accumulating fluffy high ratio snow.  The WRF is putting out up to .25 melted on ACK, and this would - if the ratios there resemble what they were in the remainder of NewEng yesterday - equate to over half a foot of snow on the island!  Though this is the most moist of the guidance, putting it into perspective with ratio certainly helps to drive home just how fine of a line we walk.  As for the synoptic situation I referenced, the vort sliding northeast over the waters just S of NewEng Thu  into Thu eve is elongated, but intense, and prompts widespread 500 mb UVM over Srn NewEng latter half of Thu.  This puts me on guard for a bit farther N progression of precip that most guidance would suggest, and keeps me very cautious that WRF may be onto something.  Additionally, this low should develop very quickly over the warm waters S and E of our South Coast, and probably will appear quite impressive.  We saw a storm quickly develop a baroclinic leaf on the south boundary of an arctic airmass with the last outbreak but it was well offshore.  This time, my concern is this happens closer to the Cape and Islands given the baroclinicity with warm ocean water and bitter cold air sfc and more importantly aloft, and while it probably still really takes off too late to nail anyone, even getting a northern fringe in its early ramp-up stage would bring a blanket of snow to far SE areas.

Farther north, I don't think we're out of the woods with conditions favorable for convective clusters, as mentioned above.  Meanwhile, the pressure gradient will tighten in response to the retrograding storm closing in on Northeastern NewEng, and this will kick winds back up later Thu through Thu night, meaning wind chill becomes more of a factor.  The continued cyclonic flow also dislodges the center of the cold air into NewEng - following its upper level polar vortex counterpart - and this will bring some of the coldest air available into Srn Quebec and Nrn NewEng, where high temps on Fri will end up below zero.  Prior to that, however, Thu night winds and cold will combine to bring chill factors to 40 below for most of the far North Country, and 20 below in even Southern NewEng!  Thu night also poses an interesting scenario weatherwise because it's the time during which the upper level low moves overhead, so I think it's wisest to keep squalls in the forecast in scattered form Thu ngt into Fri, which may affect the AM drive Fri, but given that we're working on uncertainties in the 24 hour window, would rather not get too fancy on this.

Weekend brings two vorts - one Sat AM that should be fairly light in nature for widespread light snow and departs by afternoon, then a more important one Sun AM that has more low level convergence to work with.  The 500 mb pattern actually looks great for a progressive but quickly developing storm Sunday, so I'm not sure we should relax much on that wave, tho for now will not go hog wild on it given lack of good support from guidance.  Cold shot follows early next week.  More thoughts on the longer range tomorrow.

Matt

Tuesday's Discussion:

1:05 PM:  No time today before appearance.  Bottom line for techies is that we're tracking the meso low (impressive closed signature on sfc/buoy obs and gusts to 38 mph at PVC!) as it moves toward Central Maine coast late tonight and on Wednesday after brushing Cape with perhaps a few fluffy inches Wellfleet to P'town and less farther south, steered by 850 to sfc flow.  As it combines with warm advection on Wed, this should really light the snow up around Penobscot Bay where synoptic scale isentropic lift enhances lift already present thanks to convergence and instability.  Heaviest amounts of the event may result Wed in these areas.  Elsewhere, another fluffy coating - probably less than last night, tho still probably an impressive ratio.  Ratios with last event were on the order of 30+ to 1, snow to water.

Matt

Monday's Discussions:

1:50 PM:  Update to the techie discussion (previous discussion below):  Wow.  Radar presentation of developing low off ME coast assoc with Norlun trof extremely impressive - feeder bands as of this writing are evident and sfc obs indicate a circulation that is trying to close.  If it succeeds in doing this, and continues to maintain improving presentation, the center of this meso low would have the potential to bring heavy snow if/where it makes "landfall" into the coast of ME.

1:45 PM:  Norlun trough event began earlier than I expected today across Srn ME coastline.  Passage of morning vort brought widespread snow showers dampened by dry boundary layer but left behind active Norlun trof.  Guidance has improved greatly on picking up on these events, but the concern is twofold today: 1) The amount of precipitation forecasted - expected to exceed .50" liquid equivalent, and 2) The location of these amounts, placed over the Gulf of Maine by operational guidance but verifying much farther inland in Northern York County thus far, and developing much sooner than anticipated.  Spoke with Kennebunk Police - many thanks for the info - who report snow has been moving farther inland through the day with large flakes accumulating at a steady rate.  This isn't surprising given that saturation has occurred in the dendritic crystal growth layer, which in concert with lingering arctic sfc airmass will create a quickly accumulating snow with a high ratio.  This is reason for concern, certainly, but is an event that truly is a humbling one for meteorologists.  Even though I saw the Norlun trough potential in advance, and see it developing a bit ahead of schedule now, the fact is that we're still largely at a loss as a field regarding where and when this band will drop its heaviest amounts.  At this point, given the overwhelming agreement among operational and SUNYSB MM5 guidance that the max precip stays over the waters, I'm going to continue to believe that.  Still, in today's noon show I issued an accumulation map with 3" amounts along the Maine coast from Nrn York County all the way to Knox County coast.  My reasoning for this was based upon the belief that this band will remain stationary for several hours - perhaps weakening with NVA before strengthening again in response to PVA ahead of shortwave currently moving east across Eastern Great Lakes - owing to very light wind fields in the lower levels, including 850 mb.  A west to southwest flow develops later Mon eve, and that's when I expect the band to shift east, though the area of enhanced snowfall rates is likely to expand thanks to increased dynamic lift, hence the reasoning for enhanced amounts all along the Maine coastline.  Inland by 10-15 miles, amounts will probably drop to around an inch.  Certainly there is some anxiety here, as a verification of heaviest amounts farther north would mean a tremendously higher amount of snow, while a due east shift of the Norlun trough would instead result in the higher amounts staying over water - eventually coming into line with guidance products - and hardly any more than a coating farther up the coastline.  So, I've tried to strike a conservative balance to alert folks adequately, yet not overreact, and have tried to emphasize the uncertain nature of this phenomenon in my broadcasts and in the General Wx Summary.  It does appear clear, however, that we'll be dealing with this Norlun trof in some way, shape and form through midweek!

Elsewhere, shortwave passage tonight will bring some weak interaction with moisture lifting north from main feed off Carolina coast.  This will produce widespread area of light snow, though amounts should total under an inch in just about all spots.  Again, some concern along outer Cape Ann and outer Cape Cod for enhancement due to Norlun trough, and have mentioned this in forecasts but not willing to bank on it yet given farther east development and slow eastward progression thus far.  Indications are that weak low pressure will develop along the Norlun trof Mon Ngt, and this would mean perhaps some weak ocean enhancement with easterly component in Eastern MA, where not only may highest amounts be observed, but also snow showers may linger into Tue AM.  Rest of Tue likely to bring some breaks of sun given midlvl drying, but high llvl RH combined with steadily cooling midlvl temps will create a pool of instability that will breed plenty of llvl clouds and snow showers, esp in orographically favored areas and where Norlun trof effects persist.

Warmest day of the week comes Wed in advance of powerful arctic front.  Good llvl WAA to boost temps but also will feed isentropic lift along Norlun trof, and is likely to enhance Central ME coastal snow on Wed as a result.  Arctic fropa occurs Wed afternoon and comes with decent llvl speed and directional convergence, which will bring favorable conditions for an active line of squalls in many areas.  An event like this is always a bit more tenuous in Eastern Srn NewEng, so would like to see a few more guidance runs before biting too hard, but see enuf with fcstd convergence, PVA, lift, ambient RH and airmass displacement to warrant putting them in the forecast.

Impressive surge of arctic air comes with wild retrogression of Newfoundland storm - as mentioned in General Wx Summary above, this is the same storm that's assoc with Mid-Atlantic moisture today.  Building ridge in Greenland forces storm to stall then retrograde as heights lower over Ern Canada behind it.  This mean a dump of cold and shortwaves into the trof, which is progged to sit directly over NewEng.  With so much energy, and such resultant baroclinicity sitting just S/SE of NewEng, I am so very hesitant to believe this will be a relatively quiet transition.  In fact, I don't believe that at all - there should be plenty of active weather through the period, and perhaps the greater question is whether we get a consolidated storm on the base of the trof Thu, over the waters south of NewEng for a coastal storm.  While operational models all suggest this will not be the case, a series of GFS Ensemble members do not want to let this potential go.  I've kept snow in the forecast, because even if this situation does not produce an arctic wave - which is a real possibility - we should see convective squalls beneath the cold core on Thu, and yet another round of very strong wind and cold Thu that will last thru the end of the week.

Our next wave of low pressure would be likely Sat in response to a Nrn stream wave riding the thermal ribbon laid out across the Nrn Tier of the US.

Enjoy your day!

Matt

AFTER HALF A FOOT OF SNOW FOR A FEW, NORLUN TROUGH NOT DONE YET...BITTER ARCTIC BLAST SET TO RETURN FOR ALL

Welcome to the weather blog - a regular Monday through Friday discussion of the weather!  While the discussions usually will only come on days I'm working, I'll issue special updates when the weather warrants.  I will always post to let you know when no discussion is expected if I'm away on vacation, etc. - if no update is here and no info is available, that likely means the server has temporarily gone on the fritz and I will update as soon as technically possible.  You'll find a quick weather synopsis linked to the daily forecast at the top of the page, a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow by mid-afternoon. My email is contact@mattnoyes.net.  This blog is for you, so I hope you enjoy it!  -Matt Noyes

General Weather Summary:

Though the air will turn progressively milder Tuesday into early Wednesday, this regime of increasing warmth and moisture means widespread snow showers with each upper level disturbance.  That was the result Monday night, and will be the result again Tuesday night for some.  Regarless, any warmth gained Tuesday and early Wednesday will be swept back southward with the passage of an arctic cold front Wednesday afternoon.

For now, New Englanders brushed off the snow and headed off across treated interstates and snow-covered back roads Tuesday morning, heading into what has amounted to a glistening day amidst emerging sunshine for many areas.  Though most of us across New England will find this blend of sun and clouds along with a gradually shifting wind from northwest to southwest allowing somewhat milder temperatures, exceptions are found near the coastline.  It's just off the eastern New England coast where we find a pesky and persistent feature on the weather map - a feature not all that common, but one that has a history of dropping over a foot of snow from Eastern Massachusetts to coastal Maine in some instances: The Norlun Trough.  Remember that there are two ways in which we describe a "trough" in the atmosphere.  Sometimes, the term refers to a dip in the jet stream winds flowing high in the sky and these jet stream troughs are often associated with storminess and cold weather on a regional scale, affecting entire segments of the country and the globe.  At the surface, however, a "trough" is another word for a disturbance in the atmosphere.  A trough usually features a change in wind direction along it here at ground level ("convergence" of air where the changing winds meet), along with slightly lower barometric pressure.  Converging winds can force air to rise, and when coupled with much colder air aloft than at ground level ("instability") the result often can be clouds and precipitation.  This certainly was the result yesterday, as discussed here at length, when we saw a band of snow set up along the Northern York County, ME, coastline by midday and persist while gradually expanding northeast during the overnight.  This localized band of snow, combined with the widespread snow associated with the large-scale disturbance that moved through New England, resulted in half a foot of snow for a few isolated coastal Maine locales, with more common reports of four inches!  So what is the tricky Norlun trough up to for Tuesday and Wednesday?

While the bands of snow associated with these features are very difficult to predict, it still most certainly appears as though the heaviest snow will remain over open waters east of Massachusetts and over the Gulf of Maine - at least through Tuesday.  Radar imagery has been very impressive (check it out through the links at right!) showing a well developed spiral pattern to a miniature coastal low pressure center that formed along the Norlun trough.  Each spoke of moisture rotating around this weak storm center has brought bands of light snow pivoting along the coastlines of Maine, New Hampshire and Massachusetts.  With a southward jog to the weak coastal low pressure center, the main focus of snow showers will also jog southward through Eastern Massachusetts, and eventually it's likely that the southern periphery of the low pushes steadier snow onto northern portions of Outer Cape Cod.  Because of the fluffy nature of the snow, it will pile up rather quickly, and a few fresh inches isn't out of the question from Wellfleet northward, with lesser amounts but still up to a quick, fluffy inch for the coastal plain of Eastern Massachusetts.  With the southward shift in the action during the day Tuesday, this takes the focus off of the Maine and New Hampshire seacoasts for awhile, but focus will return for some Tuesday night and Wednesday, as this Norlun trough will be slow to completely disappear from the weather map. 

All the while, a series of weak storm centers will be pulling northeast from the Great Lakes into Southern Canada, and the counter-clockwise flow of air around each of these low pressure waves will gradually feed milder air northeast into New England.  The result will be steadily moderating temperatures into the first half of Wednesday.  While, aside from the Norlun trough, this may seem like a rather quiet weather pattern, looks can be deceiving.  In fact, the very same storm that moved well southeast of New England, off the Carolina coast, on Monday won't be going far, and will have a bigger impact on our weather in the coming days than it did when it shot off the coastline!  The simple reason is a building ridge of high pressure - fair weather - over Greenland.  This ridge will stop any eastward progression of the rapidly strengthening storm, and instead cause it to slow and stall near Newfoundland.  Meanwhile, changes will be ongoing aloft.  The continued counter-clockwise swirl of this strong Canadian Maritime storm will aid in dragging deep cold air southward from Central and Northern Canada, and along with this Canadian cold will come strong energetic disturbances.  These disturbances - and the cold air - will pool just north of New England early on our warmest day of the week - Wednesday - and as the Newfoundland storm begins to back westward, the deep arctic cold will surge south.  The end result is a pool of deep cold and strong energy over New England late Wednesday through Friday, likely marked by a series of small-scale but strange events, ranging from Wednesday snow squalls ushering in the change, to a stripe of renewed accumulating snow in Central Maine along the still-present Norlun trough, to strong winds with cold air on Thursday.

The first sign of change en route to New England comes Wednesday, after a Tuesday night fresh coating of snow to most areas with the passage of a weak disturbance aloft.  Though some breaks of sun are possible during the first half of the day Wednesday, the aforementioned surge of arctic cold will be marching steadily southeast, and mild southwest winds will increase noticeably ahead of the front.  This will serve to strengthen the convergence of air along the Norlun trough as it expands northward back into the Central Coast of Maine, resulting in a renewed and hearty band of localized snow late Tuesday night through Wednesday around Knox, Hancock and Waldo Counties, where plowable snow will be likely.  Elsewhere, a relatively dry but breezy first half of Wednesday will give way to a sudden wind shift, a scattered to broken line of snow squalls, and the onslaught of arctic cold.  Temperatures will tumble Wednesday afternoon and any snow squalls that do develop will melt on area roadways, only to freeze as cold air pours in, resulting in some icy roads by late in the day.  A few of these squalls - especially across Northern and Western New England - will be heavy enough to reduce visibility to near zero as they pass through, dropping a quick inch or two of snowfall.  As cold air pushes into New England Wednesday evening and night, winds will remain quite gusty and wind chill values will drop below zero.  This installment of cold air will remain in place through Thursday, while the collection of energetic disturbances aloft continues to deposit scattered snow showers and a few heavier squalls throughout the day, and temperatures remain stuck in the single digits and lower teens north and around 20 south for daytime highs.

By Friday, the skies and wind may quiet a bit but the air will be every bit as cold.  This sets up a scenario for thickening clouds Friday night as the next upper level disturbance, caught in the steering flow of the jet stream winds aloft, traverses the Northern Plains and Great Lakes en route to New England.  This disturbance is likely to bring a period of widespread snow - mostly light - on Saturday before diminishing later in the day and giving way to a drier trend to end the weekend.

Make it a wonderful Tuesday.

Matt

Matt's Technical Meteorological Discussion: Updated Tuesday, January 23 at 1:05 PM

No time today before appearance.  Bottom line for techies is that we're tracking the meso low (impressive closed signature on sfc/buoy obs and gusts to 38 mph at PVC!) as it moves toward Central Maine coast late tonight and on Wednesday after brushing Cape with perhaps a few fluffy inches Wellfleet to P'town and less farther south, steered by 850 to sfc flow.  As it combines with warm advection on Wed, this should really light the snow up around Penobscot Bay where synoptic scale isentropic lift enhances lift already present thanks to convergence and instability.  Heaviest amounts of the event may result Wed in these areas.  Elsewhere, another fluffy coating - probably less than last night, tho still probably an impressive ratio.  Ratios with last event were on the order of 30+ to 1, snow to water.

Matt

Monday's Discussions:

1:50 PM:  Update to the techie discussion (previous discussion below):  Wow.  Radar presentation of developing low off ME coast assoc with Norlun trof extremely impressive - feeder bands as of this writing are evident and sfc obs indicate a circulation that is trying to close.  If it succeeds in doing this, and continues to maintain improving presentation, the center of this meso low would have the potential to bring heavy snow if/where it makes "landfall" into the coast of ME.

1:45 PM:  Norlun trough event began earlier than I expected today across Srn ME coastline.  Passage of morning vort brought widespread snow showers dampened by dry boundary layer but left behind active Norlun trof.  Guidance has improved greatly on picking up on these events, but the concern is twofold today: 1) The amount of precipitation forecasted - expected to exceed .50" liquid equivalent, and 2) The location of these amounts, placed over the Gulf of Maine by operational guidance but verifying much farther inland in Northern York County thus far, and developing much sooner than anticipated.  Spoke with Kennebunk Police - many thanks for the info - who report snow has been moving farther inland through the day with large flakes accumulating at a steady rate.  This isn't surprising given that saturation has occurred in the dendritic crystal growth layer, which in concert with lingering arctic sfc airmass will create a quickly accumulating snow with a high ratio.  This is reason for concern, certainly, but is an event that truly is a humbling one for meteorologists.  Even though I saw the Norlun trough potential in advance, and see it developing a bit ahead of schedule now, the fact is that we're still largely at a loss as a field regarding where and when this band will drop its heaviest amounts.  At this point, given the overwhelming agreement among operational and SUNYSB MM5 guidance that the max precip stays over the waters, I'm going to continue to believe that.  Still, in today's noon show I issued an accumulation map with 3" amounts along the Maine coast from Nrn York County all the way to Knox County coast.  My reasoning for this was based upon the belief that this band will remain stationary for several hours - perhaps weakening with NVA before strengthening again in response to PVA ahead of shortwave currently moving east across Eastern Great Lakes - owing to very light wind fields in the lower levels, including 850 mb.  A west to southwest flow develops later Mon eve, and that's when I expect the band to shift east, though the area of enhanced snowfall rates is likely to expand thanks to increased dynamic lift, hence the reasoning for enhanced amounts all along the Maine coastline.  Inland by 10-15 miles, amounts will probably drop to around an inch.  Certainly there is some anxiety here, as a verification of heaviest amounts farther north would mean a tremendously higher amount of snow, while a due east shift of the Norlun trough would instead result in the higher amounts staying over water - eventually coming into line with guidance products - and hardly any more than a coating farther up the coastline.  So, I've tried to strike a conservative balance to alert folks adequately, yet not overreact, and have tried to emphasize the uncertain nature of this phenomenon in my broadcasts and in the General Wx Summary.  It does appear clear, however, that we'll be dealing with this Norlun trof in some way, shape and form through midweek!

Elsewhere, shortwave passage tonight will bring some weak interaction with moisture lifting north from main feed off Carolina coast.  This will produce widespread area of light snow, though amounts should total under an inch in just about all spots.  Again, some concern along outer Cape Ann and outer Cape Cod for enhancement due to Norlun trough, and have mentioned this in forecasts but not willing to bank on it yet given farther east development and slow eastward progression thus far.  Indications are that weak low pressure will develop along the Norlun trof Mon Ngt, and this would mean perhaps some weak ocean enhancement with easterly component in Eastern MA, where not only may highest amounts be observed, but also snow showers may linger into Tue AM.  Rest of Tue likely to bring some breaks of sun given midlvl drying, but high llvl RH combined with steadily cooling midlvl temps will create a pool of instability that will breed plenty of llvl clouds and snow showers, esp in orographically favored areas and where Norlun trof effects persist.

Warmest day of the week comes Wed in advance of powerful arctic front.  Good llvl WAA to boost temps but also will feed isentropic lift along Norlun trof, and is likely to enhance Central ME coastal snow on Wed as a result.  Arctic fropa occurs Wed afternoon and comes with decent llvl speed and directional convergence, which will bring favorable conditions for an active line of squalls in many areas.  An event like this is always a bit more tenuous in Eastern Srn NewEng, so would like to see a few more guidance runs before biting too hard, but see enuf with fcstd convergence, PVA, lift, ambient RH and airmass displacement to warrant putting them in the forecast.

Impressive surge of arctic air comes with wild retrogression of Newfoundland storm - as mentioned in General Wx Summary above, this is the same storm that's assoc with Mid-Atlantic moisture today.  Building ridge in Greenland forces storm to stall then retrograde as heights lower over Ern Canada behind it.  This mean a dump of cold and shortwaves into the trof, which is progged to sit directly over NewEng.  With so much energy, and such resultant baroclinicity sitting just S/SE of NewEng, I am so very hesitant to believe this will be a relatively quiet transition.  In fact, I don't believe that at all - there should be plenty of active weather through the period, and perhaps the greater question is whether we get a consolidated storm on the base of the trof Thu, over the waters south of NewEng for a coastal storm.  While operational models all suggest this will not be the case, a series of GFS Ensemble members do not want to let this potential go.  I've kept snow in the forecast, because even if this situation does not produce an arctic wave - which is a real possibility - we should see convective squalls beneath the cold core on Thu, and yet another round of very strong wind and cold Thu that will last thru the end of the week.

Our next wave of low pressure would be likely Sat in response to a Nrn stream wave riding the thermal ribbon laid out across the Nrn Tier of the US.

Enjoy your day!

Matt

WIDESPREAD SNOW SHOWERS EN ROUTE WHILE "NORLUN TROUGH" BRINGS LOCALIZED HEAVIER SNOW TO MAINE COAST

Welcome to the weather blog - a regular Monday through Friday discussion of the weather!  While the discussions usually will only come on days I'm working, I'll issue special updates when the weather warrants.  I will always post to let you know when no discussion is expected if I'm away on vacation, etc. - if no update is here and no info is available, that likely means the server has temporarily gone on the fritz and I will update as soon as technically possible.  You'll find a quick weather synopsis linked to the daily forecast at the top of the page, a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow by mid-afternoon. My email is contact@mattnoyes.net.  This blog is for you, so I hope you enjoy it!  -Matt Noyes

General Weather Summary:

A round of light morning snow came as one energetic disturbance moved over New England.  Another is slated for Monday evening, before a warming trend through midweek.  Any warmth gained in the next couple of days will be quickly whisked away for the end of the week, however, with another slug of arctic air en route.

In the meantime, Monday morning snow was quite light - many areas still finding visibility between two and nine miles and only a sugarcoating of snow to speak of.  Still, with cold roads this made a few surfaces a bit slippery for a time.  This light snow was the result of a disturbance aloft, rushing eastward in the jet stream winds - the fast corridor of air high in the sky that steers our storms and acts as a thermostat, separating cold air to the north from warm to the south.  Clearly, the jet stream has been dipped south of New England for several days running, and this cold pattern is expected to continue for at least a couple more weeks.  What a pattern like this favors is a continued supply of deep arctic cold, and also the possibility of moisture input from the Pacific and Gulf of Mexico, bringing chances for snow.  But in order for snowstorms to come to fruition, the moisture and cold must both move into New England at the same time, and that remains rather difficult to do!  Monday morning's disturbance is a great example - plenty of energy, but not much moisture, and dry air in the lowest few thousand feet of the atmosphere evaporated many of the snowflakes upon descent, resulting only in very light snow.  After a break in the action for most of the day Monday, with plenty of clouds and only a few flurries, the next disturbance in line will move into New England Monday evening and night.  Though this disturbance also will be moisture-starved, there is plenty of moisture streaming off the Carolina coastline.  Though the bulk of this moisture will remain well south of New England and consolidate around a strengthening storm center that will be moving out across the Western Atlantic, our new disturbance moving overhead will interact just enough with this southern storm to pull moisture northward over New England.  The result will be a broad area of light snow for most of the six-state region Monday evening and Monday night, dropping a solid coating for most areas.  Just offshore, however, things get a bit trickier, as the result of this interaction will be evident - a Norlun trough.  What is a Norlun trough?  Near the surface and in the lower few thousand feet of the atmosphere, a trough is a weak disturbance featuring a wind shift and convergence of air - that is, air coming together.  Occasionally, with cold air aloft, conditions can become quite favorable for clouds and precipitation ("instability") and it's this combination of converging air and instability that makes a Norlun trough.  These events have, in the past, deposited surprise snowfalls of over a foot from the Eastern Massachusetts coastline through the coast of Maine.  In this instance, it appears as though the heavier band of snow associated with the Norlun trough will set up mostly offshore, but close enough to New England that it's worth noting the potential for enhanced accumulations on outer portions of Cape Ann and Outer Cape Cod, and it's not impossible that this band could extend into the Central coast of Maine - in fact, that's looking more and more likely given a band of snow that's already established around the York County coast!  While the bulk of this heavier snow band will remain just offshore, over the Gulf of Maine and waters east of Massachusetts, a few inches are possible along the immediate coast from Northern York County, ME, to the Knox County coastline between Monday midday and overnight Monday night.  Keep in mind that these bands of snow are very difficult to predict, but those along the immediate coastline should be prepared for enhanced accumulation of a few inches in the areas mentioned.

This Norlun trough will be slow to completely disappear from the weather map, as a series of upper level disturbances moving overhead will enhance it for the next day or two.  Nonetheless, Tuesday is likely to bring early lingering snow showers to Eastern New England, and otherwise lots of clouds, some sunny breaks and scattered snow showers to most of New England as weak disturbances continue to ride overhead in the jet stream winds aloft.  All the while, a series of weak storm centers will be pulling northeast from the Great Lakes into Southern Canada, and the counter-clockwise flow of air around each of these low pressure waves will gradually feed milder air northeast into New England.  The result will be steadily moderating temperatures into Wednesday.

While this may seem like a rather quiet weather pattern, looks can be deceiving.  In fact, the very same storm that moves well Southeast of New England, off the Carolina coast, on Monday won't go far.  The simple reason is a building ridge of high pressure - fair weather - over Greenland.  This ridge will stop any eastward progression of the rapidly strengthening storm, and instead cause it to slow and stall near Newfoundland.  Meanwhile, changes will be ongoing aloft.  The continued counter-clockwise swirl of this strong Canadian Maritime storm will aid in dragging deep cold air southward from Central and Northern Canada, and along with this Canadian cold will come strong energetic disturbances.  These disturbances - and the cold air - will pool just north of New England on our warmest day of the week - Wednesday - and as the Newfoundland storm begins to back westward, the deep arctic cold will surge south.  The end result is a pool of deep cold and strong energy over New England on Thursday, likely marked by a series of small-scale but strange events, ranging from Wednesday snow squalls ushering in the change, to a Wednesday stripe of accumulating snow in Central Maine along the still-present Norlun trough, to strong winds with cold air on Thursday.

With so much energy and cold air in place, I'm also on-guard for storm development Thursday, though at this point it appears anything would likely be too far south and east to affect New England.  Nonetheless, it will be a very windy Thursday as arctic air locks in, and this arctic cold will last through Friday and into the weekend.

Matt

Matt's Technical Meteorological Discussion: Updated Monday, January 22 at 1:50 PM

Update to the techie discussion (previous discussion below):  Wow.  Radar presentation of developing low off ME coast assoc with Norlun trof extremely impressive - feeder bands as of this writing are evident and sfc obs indicate a circulation that is trying to close.  If it succeeds in doing this, and continues to maintain improving presentation, the center of this meso low would have the potential to bring heavy snow if/where it makes "landfall" into the coast of ME.

1:45 PM:  Norlun trough event began earlier than I expected today across Srn ME coastline.  Passage of morning vort brought widespread snow showers dampened by dry boundary layer but left behind active Norlun trof.  Guidance has improved greatly on picking up on these events, but the concern is twofold today: 1) The amount of precipitation forecasted - expected to exceed .50" liquid equivalent, and 2) The location of these amounts, placed over the Gulf of Maine by operational guidance but verifying much farther inland in Northern York County thus far, and developing much sooner than anticipated.  Spoke with Kennebunk Police - many thanks for the info - who report snow has been moving farther inland through the day with large flakes accumulating at a steady rate.  This isn't surprising given that saturation has occurred in the dendritic crystal growth layer, which in concert with lingering arctic sfc airmass will create a quickly accumulating snow with a high ratio.  This is reason for concern, certainly, but is an event that truly is a humbling one for meteorologists.  Even though I saw the Norlun trough potential in advance, and see it developing a bit ahead of schedule now, the fact is that we're still largely at a loss as a field regarding where and when this band will drop its heaviest amounts.  At this point, given the overwhelming agreement among operational and SUNYSB MM5 guidance that the max precip stays over the waters, I'm going to continue to believe that.  Still, in today's noon show I issued an accumulation map with 3" amounts along the Maine coast from Nrn York County all the way to Knox County coast.  My reasoning for this was based upon the belief that this band will remain stationary for several hours - perhaps weakening with NVA before strengthening again in response to PVA ahead of shortwave currently moving east across Eastern Great Lakes - owing to very light wind fields in the lower levels, including 850 mb.  A west to southwest flow develops later Mon eve, and that's when I expect the band to shift east, though the area of enhanced snowfall rates is likely to expand thanks to increased dynamic lift, hence the reasoning for enhanced amounts all along the Maine coastline.  Inland by 10-15 miles, amounts will probably drop to around an inch.  Certainly there is some anxiety here, as a verification of heaviest amounts farther north would mean a tremendously higher amount of snow, while a due east shift of the Norlun trough would instead result in the higher amounts staying over water - eventually coming into line with guidance products - and hardly any more than a coating farther up the coastline.  So, I've tried to strike a conservative balance to alert folks adequately, yet not overreact, and have tried to emphasize the uncertain nature of this phenomenon in my broadcasts and in the General Wx Summary.  It does appear clear, however, that we'll be dealing with this Norlun trof in some way, shape and form through midweek!

Elsewhere, shortwave passage tonight will bring some weak interaction with moisture lifting north from main feed off Carolina coast.  This will produce widespread area of light snow, though amounts should total under an inch in just about all spots.  Again, some concern along outer Cape Ann and outer Cape Cod for enhancement due to Norlun trough, and have mentioned this in forecasts but not willing to bank on it yet given farther east development and slow eastward progression thus far.  Indications are that weak low pressure will develop along the Norlun trof Mon Ngt, and this would mean perhaps some weak ocean enhancement with easterly component in Eastern MA, where not only may highest amounts be observed, but also snow showers may linger into Tue AM.  Rest of Tue likely to bring some breaks of sun given midlvl drying, but high llvl RH combined with steadily cooling midlvl temps will create a pool of instability that will breed plenty of llvl clouds and snow showers, esp in orographically favored areas and where Norlun trof effects persist.

Warmest day of the week comes Wed in advance of powerful arctic front.  Good llvl WAA to boost temps but also will feed isentropic lift along Norlun trof, and is likely to enhance Central ME coastal snow on Wed as a result.  Arctic fropa occurs Wed afternoon and comes with decent llvl speed and directional convergence, which will bring favorable conditions for an active line of squalls in many areas.  An event like this is always a bit more tenuous in Eastern Srn NewEng, so would like to see a few more guidance runs before biting too hard, but see enuf with fcstd convergence, PVA, lift, ambient RH and airmass displacement to warrant putting them in the forecast.

Impressive surge of arctic air comes with wild retrogression of Newfoundland storm - as mentioned in General Wx Summary above, this is the same storm that's assoc with Mid-Atlantic moisture today.  Building ridge in Greenland forces storm to stall then retrograde as heights lower over Ern Canada behind it.  This mean a dump of cold and shortwaves into the trof, which is progged to sit directly over NewEng.  With so much energy, and such resultant baroclinicity sitting just S/SE of NewEng, I am so very hesitant to believe this will be a relatively quiet transition.  In fact, I don't believe that at all - there should be plenty of active weather through the period, and perhaps the greater question is whether we get a consolidated storm on the base of the trof Thu, over the waters south of NewEng for a coastal storm.  While operational models all suggest this will not be the case, a series of GFS Ensemble members do not want to let this potential go.  I've kept snow in the forecast, because even if this situation does not produce an arctic wave - which is a real possibility - we should see convective squalls beneath the cold core on Thu, and yet another round of very strong wind and cold Thu that will last thru the end of the week.

Our next wave of low pressure would be likely Sat in response to a Nrn stream wave riding the thermal ribbon laid out across the Nrn Tier of the US.

Enjoy your day!

Matt

WEEKEND COLD STREAMS IN ON POTENTIALLY DAMAGING WIND...MULTIPLE STORM POSSIBILITIES NEXT WEEK

Welcome to the weather blog - a regular Monday through Friday discussion of the weather!  While the discussions usually will only come on days I'm working, I'll issue special updates when the weather warrants.  I will always post to let you know when no discussion is expected if I'm away on vacation, etc. - if no update is here and no info is available, that likely means the server has temporarily gone on the fritz and I will update as soon as technically possible.  You'll find a quick weather synopsis linked to the daily forecast at the top of the page, a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow by mid-afternoon. My email is contact@mattnoyes.net.  This blog is for you, so I hope you enjoy it!  -Matt Noyes

General Weather Summary:

A series of energetic disturbances will merge into a powerhouse storm east of Maine heading into the weekend, delivering a shot of heavy snow to interior Central and Eastern Maine, and bringing damaging winds to New England to start the weekend.

Moisture that streamed across Southeastern New England as rainfall fed over the Gulf of Maine and into Eastern Maine on Friday, while energy aloft was evidenced by a band of light snow marching east across Southern New England that remained transient and has continued shipping off the coastline.  Meanwhile, another energetic disturbance trudging east out of New York State carries snow showers with it, and along the Western slopes of the Green Mountains, the Berkshires and the Litchfield Hills, these snow showers will gain additional vigor as strengthening westerly winds push up against the mountain faces, resulting in "upslope flow," as air is forced upward upon hitting the mountains, resulting in heavier squalls.  In fact, along the spine of the Green Mountains, 4"-6" of snow will fall Friday and Friday night, with higher amounts possible around Jay Peak!  These snow showers will expand east across the White Mountains and Western Maine Mountains later Friday through Friday night, depositing a general 2" of snow to these areas with higher amounts on favored west and northwest facing mountainslopes.  Farther south, expect a mainly dry day with some sunshine in Central and Southern New England to give way to a noticeably strengthening wind Friday evening.

This wind cranks up as the moisture and two energetic disturbances all merge just east of Maine.  The result will be a "bombing" storm - that is, a storm that strengthens rapidly - and winds will crank through Friday night as a result.  As winds blow from the northwest and west in the counter-clockwise flow around this intensifying storm, gusts will reach 35 mph Friday evening, 45 mph Friday Night, and as high as 50 mph on Saturday.  Winds of this force would result in some potential damage to tree limbs, and therefore new power outages would be possible for some communities across New England on Saturday.  This also will create areas of blowing snow for the Green Mountains, and for Eastern and interior Central Maine, where the jackpot of Friday snow will have fallen with a few inches north of Bangor, near half a foot by Millinocket, and up to 10" near Houlton.  Along the coastline, much less snow will have fallen thanks to a well defined coastal front that allowed warm ocean air to turn precipitation to rain when it fell Friday, and farther west the precipitation shield never penetrated far enough north.  For the remainder of New England, however, wind will not result in plowed roads filling back in with snow, but still will create biting wind chills with temperatures in the 20s south and teens north, and wind gusts to 50 mph bringing the chill factor below zero north and into the single digits to around ten above south.  Scattered snow showers will be possible in most areas as cold air will be present aloft, and this will mean plenty of clouds blotting out the sunshine for a good chunk of the day.

Winds will remain active Saturday night and Sunday as the storm east of Maine continues to churn, and therefore continues to pump arctic air southward.  Still, winds should drop below damaging criteria overnight Saturday night and are not expected to peak that high again on Sunday as the responsible storm weakens gradually.  Nonetheless, wind chill values will still be rather brutal on Sunday with temperatures in the 20s and gusts to 35 mph.

Heading into early next week, the East Coast remains in a "trough" in the jet stream winds aloft.  Remember that the term "trough" is used to describe a dip in the jet stream winds aloft - the fast corridor of air that flows high in the sky and steers storm systems along it, also acting as a thermostat for the atmosphere, separating cold to the north from warm to the south. With a trough over the Eastern United States, this keep us on the north side of the jet stream, with a tendency for cold air to remain locked in place and storms to move south of us, meaning we'd be on the cold northern side of precipitation shields.  The biggest question in a pattern like this is whether interaction occurs between cold and energetic Canadian systems dropping down from the north, and southern stream systems loaded with mositure, and if that interaction occurs, the next challenge is to determine how quickly any storm would develop, and how far north the cold precipitation shield would extend.  Though Monday looks fairly quiet at this point - with increasing clouds and slightly milder air - Tuesday is likely to bring some interaction of a nearby northern and southern stream disturbance.  This will result in the development of something called an "inverted trough" in the atmosphere - in other words, a weak disturbance that develops and links two otherwise separate disturbances - in this case, one to the south from one to our northwest.  Along this feature, I expect snow to develop on Tuesday, though the intensity of this snow depends on whether another small storm center can develop amidst the "inverted trough."  If a small storm center can develop, amounts would be enhanced considerably.

By Thursday, another disturbance will near New England and bring a returning chance of wintry weather, though the stakes are high on that storm - that is, at this point the pattern favors storm development Thursday but indications from our guidance are nil, meaning it's a tough situation to forecast for, but could deliver a strong storm given the pattern of an East Coast trough and strong arctic air nearby. In the meantime, I'm extending my confidence in this below to, at times, much below normal winter pattern with favorable setup for snow in New England from at least early February, to at least mid-February.  Winter has finallly arrived, and is here for an extended stay!

Technical Discussion:  None today.  Enjoy your weekend.

Matt

Matt's Technical Meteorological Discussion: Updated Wednesday, January 17 at 1:50 PM

Focus today will be on the end-of-week storm.  Let's review what we know before we confuse ourselves with what we don't know:  Northern stream shortwave will dive southeast thru the Upper Ohio Valley and will dig at base of Great Lakes trof.  Meanwhile, Srn stream wave responsible for TX winter wx today will push off the Carolina coast where it will induce sfc cyclone development.  Steering flow will back in the mid-lvls and this will assist in carrying sfc wave and assoc Gulf moisture northward along the coast, and along inverted trof well modeled by guidance that develops in advance of eastward shifting longwave trof.  When the two vort maxes merge, intense and rapid cyclogenesis will result.  The question, of course, revolves around when the happens, not to mention the question of thermal profile.  But let's focus on the merger and resultant intensification first.  The NMM continues to ring the bell of a major merger that will occur earlier in the game, bottoming the low into the 970-980 mb range as it moves E of MA.  The implications of such a quick development would be a better developed and more rapid wraparound precip shield, and a 0 C isotherm crashing toward the coast.  The other result would be a more intense and expansive wind field, capable of delivering damaging winds to much of New England.  While this is an ominous (or fun, depending on your outlook) portrayal of the storm development, at this point it is the lone guidance product on this course.  We have certainly seen the NMM pull out some biggies in the past - and, in fact, those of you who read regularly know that I have gone with the NMM in the past even when it's been the "sole provider" of what I'd expected to see.  In this case, however, I'm a bit skeptical of buying the NMM lock, stock and barrel, largely because there has been good agreement on a relatively progressive system from the start, at least until the storm reaches the northern Gulf of ME and moves E of ME, when it will slow and bomb. Until that point, though, it is being carried by 50-70 kt midlvl flow, and I still like a progressive scenario.  This would mean a shot of warm advection precip to most of NewEng Thu Ngt into Fri AM, spreading from S to N and focused along the inverted trof where it will probably progress even a bit faster than currently progged.  This inverted trof will become the coastal front in time, and will focus the QPF production through interior NewEng.  Favoring a broad shield of precip, and also favoring the NMM's idea of quicker intensification if the storm center can slow down enough, is a tremendously diffluent upper level flow.  Though right now I don't see that resulting in the quick bombing shown on the NMM, I do see that as helping precip production significantly across much of Southern NewEng.  Of course, another major question is the thermal profile.  With a developing SE flow on Cape Cod as soon as Thu eve, I don't see much hope for anything but rain there. Elsewhere, however, a burst of snow is likely with the warm advection as the incoming moisture collides with our cold and dry air in place. It's the same cold and dry nature of the antecedent airmass that was my reasoning yesterday for placing the coastal front a bit farther east than the guidance would suggest.  While the Canadian global and regional are both insistent upon a rain/snow line not far from the coast, this is likely a bit too far *east*, while the NMM is likely penetrating the ocean warmth a bit too far *west*.  The end result will likely be a rain/snow line that sets up as a removed coastal front from somewhere near HFD to ORH to ASH to PWM.  This is subject to tweaking, of course, but is a preliminary estimate with heavist QPF amounts just on the cold side of this front.  I do believe this storm will ramp up quickly to deliver a strong blow to ME, where over a foot of snow is a strong possibility in the mountains Friday.  Strong winds settle in behind the storm and usher in next arctic airmass.

Matt

Tuesday's Discussion:

1:10 PM:  Cold air is obviously taking hold with rapid temp drops across SCoastal locales.  Most of these areas saw drying of road moisture before the rapid temp drop but some areas of black ice possible.  Bigger concern, of course, is the falling ice and falling limbs/lines of Srn NH and Nrn MA that will continue to cause power outages and stiff wind driving chills below zero will make for difficult utility work this eve.

While this is the concern from a public perspective, there is little from a forecasting perspective left with this storm and attn now turns to the cold and then Fri storm.  Regarding the cold, the air pouring south from Quebec - when compared with low-level thickness values and boundary layer temps - has been producing daily highs of 5 degrees or less, at least for the air that will be in place to the MA Turnpike. So, if we were dealing with snow cover that would be the rule I would follow, but that cold will moderate as it moves south over unfrozen ground and displaces the mild antecendent air in Southern New England, while even Central New Eng - though encased in ice for some areas - will see downsloping flow assisting in airmass modification, as well. With Richardson Numbers high enough for deep mixing, there will also be some adiabatic warming of the airmass, and we should be able to rise into the teens for Southern NewEng on Wed.  Farther north - and esp near the Canadian border - the airmass will be more true to its original form and therefore temps will struggle to rise above 0. Pressure gradient will mean winds stay up Tue Ngt and Wed, and this wind/cold combo will be a brutal delivery of -20 to -30 chill to Nrn NewEng Tue Ngt and still close to -20 Wed, while Srn areas will hover at -5 to -15.

Cold air well entrenched enuf to prohibit quick warmup Thu tho significant moderation will take place.  Clouds will incr at high and mid altitudes with upper level WAA later in the day, and this will further limit pot'l for temp rise.  Nrn and srn stream interaction looks quite likely Thu Ngt and Fri to create a quickly strengthening wave up the Ern seaboard that will bring snow to the interior.  Along coastline and far Srn NewEng, SE component of boundary layer wind will bring in anomalously warm SST altered air to allow for rain at coastal plain.  That said, believe NMM is probably too far W in its 12Z run and over-amplifying the effects of ocean warmth, which means its progged rn/sn line also penetrates too far inland.  Could see much of Srn CT/RI/SE MA and even coastal plain of MA warming, but also would expect to see development of coastal front that will result in farther E ptype line, and also would shift llvl deformation band closer to coast for max QPF amounts.  Next arctic blast follows and am going some 15-20 degrees below MOS guidance for Sat!

That's the gist of my thinking right now - off to a public appearance so will have to stop here for today.

Matt

THURSDAY NIGHT MIX WILL LEAVE SLIPPERY FRIDAY COMMUTE FOR MANY...COLD RESURGENT FOR WEEKEND

Welcome to the weather blog - a regular Monday through Friday discussion of the weather!  While the discussions usually will only come on days I'm working, I'll issue special updates when the weather warrants.  I will always post to let you know when no discussion is expected if I'm away on vacation, etc. - if no update is here and no info is available, that likely means the server has temporarily gone on the fritz and I will update as soon as technically possible.  You'll find a quick weather synopsis linked to the daily forecast at the top of the page, a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow by mid-afternoon. My email is contact@mattnoyes.net.  This blog is for you, so I hope you enjoy it!  -Matt Noyes

General Weather Summary:

Quick note:  Today, Thursday, is our NECN/American Red Cross "Celebrate the Gift of Life" Blood Drive.  I'm honored that the American Red Cross has asked me to be their spokesman for this event for the third year in a row, and I've donated my unit of blood!  Anyone interested in donating tomorrow should call 800-GIVE-LIFE to either make an appointment, or to find a Donor Center near to you.  Thanks to all who do come out and make a give the gift of life to patients in need across New England!  I'm heading out to report live from one of our donor centers, so today's weather update is below, issued early.

Thursday morning sunshine and frigid conditions will give way to increasing clouds, but moderating temperatures, with the approach of another energetic disturbance.  Ahead of this disturbance, the milder air streaming northward will quickly modify our brief shot of intense cold.  Meanwhile, the storm that dropped a wintry mess across Dallas on Wednesday will be racing to the Carolina coastline.  Here, this already Pacific moisture-laden storm will interact with a steady supply of Gulf moisture, and the storm will grow legs as it heads northward.  Aloft, the jet stream pattern will favor quick development of the storm, and the key to the forecast right now is twofold: 1) How quickly does the storm strengthen, and 2) How much warm is is brought it off of the Atlantic?  The answer to the first question comes from the knowledge that atmospheric conditions are ripe for rapid storm strengthening, but only once the southern moisture and northern energy dropping east out of the Great Lakes merge sufficiently.  At this point, it appears to me as though this merger won't be complete until the storm center is moving into the Gulf of Maine, which implies a shot of precipitation for Southern New England Thursday night into early Friday, then tapering as winds turn fierce later in the day.  Farther north, a more prolonged period of precipitation would result, especially across interior Maine as the storm strengthens quickly while pushing north out of the Gulf of Maine.  This leaves the door open for a significant winter storm through much of Maine that would last through a good chunk of Friday, while farther south, the initial surge of precipitation will be highly dependent upon temperatures.  Right now, it appears as though precipitation would develop across Southern New England overnight Thursday night - especially after midnight.  With a southeast wind near the surface, and ocean temperatures to our southeast running well into the 40s, warm air will flood the coastal plain, allowing almost all rain on Cape Cod, Southeast MA, Rhode Island and a lot of Connecticut. Farther north and west, cold air will hold on longer, and a period of snow is likely in most areas Thursday night - beginning as a mix after 8 PM (follow the precipitation on radar links at right), then chaning to interior snow that would drop 2"-4" of quick snow before tapering Friday morning.  Just on the cold side of this rain/snow line - a coastal front - will be where the heaviest snow falls, and this is likely to stretch from just east of the Pioneer Valley to central Worcester County to interior New Hampshire, then into the mountains of Maine.  In the mountains of Maine, at least a half foot of snow would be possible, and we may approach those amounts in the mountains of NH and the Lakes Region, but farther south along the axis we'd fall closer to the 2"-4" range.  Contrary to the previous storm, I don't see this as a mix event - it should be either rain or snow, with a clear-cut transition from one type to the other. 

This storm will strengthen quickly on Friday while pulling into Eastern Canada, and will bring very strong northerly, then westerly, winds behind it, meaning another southward surge of Canadian cold behind the storm, arriving in time for the weekend, when temperatures will plunge back below normal by several degrees.  In the longer range, we'll remain in a pattern of East Coast "troughing" for awhile. Remember that the term "trough" is used to describe a dip in the jet stream winds aloft - the fast corridor of air that flows high in the sky and steers storm systems along it, also acting as a thermostat for the atmosphere, separating cold to the north from warm to the south. With a trough over the Eastern United States, this keep us on the north side of the jet stream, with a tendency for cold air to remain locked in place and storms to move south of us, meaning we'd be on the cold northern side of precipitation shields.  This may evidence itself as the deeper weekend cold begins to pull gradually away from New England, with a storm ready to ride near the Eastern Seaboard, and a chance of snow by the beginning of next week.

In the meantime, winter-lovers can continue to rejoice at the presence of a pattern that will bring an average period of below - with intervals of much below - normal temperatures through the start of February, and a pattern that at least puts New England in a spot where big snows are a distinct possibility with Pacific and Gulf moisture close to us, and repeated spurts of deep cold and northern energy.

Matt

Matt's Technical Meteorological Discussion: Updated Wednesday, January 17 at 1:50 PM

Focus today will be on the end-of-week storm.  Let's review what we know before we confuse ourselves with what we don't know:  Northern stream shortwave will dive southeast thru the Upper Ohio Valley and will dig at base of Great Lakes trof.  Meanwhile, Srn stream wave responsible for TX winter wx today will push off the Carolina coast where it will induce sfc cyclone development.  Steering flow will back in the mid-lvls and this will assist in carrying sfc wave and assoc Gulf moisture northward along the coast, and along inverted trof well modeled by guidance that develops in advance of eastward shifting longwave trof.  When the two vort maxes merge, intense and rapid cyclogenesis will result.  The question, of course, revolves around when the happens, not to mention the question of thermal profile.  But let's focus on the merger and resultant intensification first.  The NMM continues to ring the bell of a major merger that will occur earlier in the game, bottoming the low into the 970-980 mb range as it moves E of MA.  The implications of such a quick development would be a better developed and more rapid wraparound precip shield, and a 0 C isotherm crashing toward the coast.  The other result would be a more intense and expansive wind field, capable of delivering damaging winds to much of New England.  While this is an ominous (or fun, depending on your outlook) portrayal of the storm development, at this point it is the lone guidance product on this course.  We have certainly seen the NMM pull out some biggies in the past - and, in fact, those of you who read regularly know that I have gone with the NMM in the past even when it's been the "sole provider" of what I'd expected to see.  In this case, however, I'm a bit skeptical of buying the NMM lock, stock and barrel, largely because there has been good agreement on a relatively progressive system from the start, at least until the storm reaches the northern Gulf of ME and moves E of ME, when it will slow and bomb. Until that point, though, it is being carried by 50-70 kt midlvl flow, and I still like a progressive scenario.  This would mean a shot of warm advection precip to most of NewEng Thu Ngt into Fri AM, spreading from S to N and focused along the inverted trof where it will probably progress even a bit faster than currently progged.  This inverted trof will become the coastal front in time, and will focus the QPF production through interior NewEng.  Favoring a broad shield of precip, and also favoring the NMM's idea of quicker intensification if the storm center can slow down enough, is a tremendously diffluent upper level flow.  Though right now I don't see that resulting in the quick bombing shown on the NMM, I do see that as helping precip production significantly across much of Southern NewEng.  Of course, another major question is the thermal profile.  With a developing SE flow on Cape Cod as soon as Thu eve, I don't see much hope for anything but rain there. Elsewhere, however, a burst of snow is likely with the warm advection as the incoming moisture collides with our cold and dry air in place. It's the same cold and dry nature of the antecedent airmass that was my reasoning yesterday for placing the coastal front a bit farther east than the guidance would suggest.  While the Canadian global and regional are both insistent upon a rain/snow line not far from the coast, this is likely a bit too far *east*, while the NMM is likely penetrating the ocean warmth a bit too far *west*.  The end result will likely be a rain/snow line that sets up as a removed coastal front from somewhere near HFD to ORH to ASH to PWM.  This is subject to tweaking, of course, but is a preliminary estimate with heavist QPF amounts just on the cold side of this front.  I do believe this storm will ramp up quickly to deliver a strong blow to ME, where over a foot of snow is a strong possibility in the mountains Friday.  Strong winds settle in behind the storm and usher in next arctic airmass.

Matt

Tuesday's Discussion:

1:10 PM:  Cold air is obviously taking hold with rapid temp drops across SCoastal locales.  Most of these areas saw drying of road moisture before the rapid temp drop but some areas of black ice possible.  Bigger concern, of course, is the falling ice and falling limbs/lines of Srn NH and Nrn MA that will continue to cause power outages and stiff wind driving chills below zero will make for difficult utility work this eve.

While this is the concern from a public perspective, there is little from a forecasting perspective left with this storm and attn now turns to the cold and then Fri storm.  Regarding the cold, the air pouring south from Quebec - when compared with low-level thickness values and boundary layer temps - has been producing daily highs of 5 degrees or less, at least for the air that will be in place to the MA Turnpike. So, if we were dealing with snow cover that would be the rule I would follow, but that cold will moderate as it moves south over unfrozen ground and displaces the mild antecendent air in Southern New England, while even Central New Eng - though encased in ice for some areas - will see downsloping flow assisting in airmass modification, as well. With Richardson Numbers high enough for deep mixing, there will also be some adiabatic warming of the airmass, and we should be able to rise into the teens for Southern NewEng on Wed.  Farther north - and esp near the Canadian border - the airmass will be more true to its original form and therefore temps will struggle to rise above 0. Pressure gradient will mean winds stay up Tue Ngt and Wed, and this wind/cold combo will be a brutal delivery of -20 to -30 chill to Nrn NewEng Tue Ngt and still close to -20 Wed, while Srn areas will hover at -5 to -15.

Cold air well entrenched enuf to prohibit quick warmup Thu tho significant moderation will take place.  Clouds will incr at high and mid altitudes with upper level WAA later in the day, and this will further limit pot'l for temp rise.  Nrn and srn stream interaction looks quite likely Thu Ngt and Fri to create a quickly strengthening wave up the Ern seaboard that will bring snow to the interior.  Along coastline and far Srn NewEng, SE component of boundary layer wind will bring in anomalously warm SST altered air to allow for rain at coastal plain.  That said, believe NMM is probably too far W in its 12Z run and over-amplifying the effects of ocean warmth, which means its progged rn/sn line also penetrates too far inland.  Could see much of Srn CT/RI/SE MA and even coastal plain of MA warming, but also would expect to see development of coastal front that will result in farther E ptype line, and also would shift llvl deformation band closer to coast for max QPF amounts.  Next arctic blast follows and am going some 15-20 degrees below MOS guidance for Sat!

That's the gist of my thinking right now - off to a public appearance so will have to stop here for today.

Matt