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Skiers' and Snowmobilers' Delight In Store...Sloppy Mess For Southern New England

Welcome to the weather blog - a regular Monday through Friday discussion of the weather!  You'll find a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow. If no technical discussion is available when you check in during the morning, check back later as it often comes after the Weather Summary - I try to indicate at the end of the general weather summary when/if a technical discussion is coming. My email is contact@mattnoyes.net.  While the discussions usually will only come on days I'm working, I'll occasionally issue special updates when the weather warrants.  This blog is for you, so I hope you enjoy it!  -Matt Noyes

For latest radar imagery, to check for watches and warnings, and for links to sites in the world of weather, feel free to click over to my website: www.mattnoyes.net

Matt's Weather Summary: 

11:30 AM Update:  Accumulation maps updated at bottom of Weather Summary.

After a mostly clear and frigid start to our Thursday with temperatures either side of zero, Thursday has begun with cold sunshine as our protective bubble of arctic high pressure, centered in Canada, remains in charge.  Slowly, though, this protective airmass will begin to erode from the top down today.  In it's place will come moisture...streaming up from the south in advance of the developing Southeastern U.S. storm center...and clouds will spill into New England high in the sky through the day on Thursday.  In the world of meteorology, these are called "cirrus" clouds, and indicate that moisture is moving in aloft and *may* indicate precipitation within 18 to 36 hours.  That rule should hold true in this instance.  These increasing Thursday clouds will temper just how much communities can warm up across New England, and average high temperatures will likely not make it to the freezing mark...holding in the upper 20's for most, and in the teens yet again across the North Country.  With the axis of high pressure drifting overhead, winds will be light, and this lack of atmospheric "mixing" that wind usually provides will further limit just how much we can warm up.

Thursday surface analysis shows the storm we've been anticipating, already developed and pulling plenty of moisture out of the Gulf of Mexico as the center of low pressure makes a morning pass over the Florida Panhandle.  The moisture field ahead of this storm is expansive, and the cirrus clouds we see across New England Thursday afternoon will indeed be the leading edge to this storm's moisture.  Thursday night, this southern storm center will carry its moisture north and east, and the center passes over North Carolina, delivering a hearty blow of sleet and freezing rain to the Appalachian Mountain Chain.  Meanwhile, across the Upper Great Lakes and Upper Midwest, an energetic disturbance aloft in the atmosphere will be stalling out and spinning.  The counterclockwise flow of air around this disturbance will help to create a trough, or dip in the jet stream winds aloft that steer storm systems and act as a thermostat for the atmosphere - separating warm air to the south from cold air to the north.  This new jet stream configuration will mean the steering winds will be U-shaped...making a dip across the Ohio Valley where new disturbances will shoot east, and a flow from south to north along the Eastern Seaboard.  The end result of this pattern will be to pull the storm center off the Southeast Coast northward with its significant moisture feed from the Gulf of Mexico and the Atlantic, and for this storm to interact with a new bundle of upper level energy ejecting out of the Ohio Valley.  Once again, much like one week ago, we will watch as energy and moisture converge over New England.  The difference this time is that there is much less northern energy to work with, but moisture will still be plentiful - the overall result will be a less intense but still potent system.

As moisture continues to surge northward late Thursday night and through the predawn hours of Friday, snow will develop for most of Southern and Western New England.  This cold air is quite dense, and will be difficult to move, but a persistent flow of warm air off the ocean, and warm air moving in aloft, will erode the cold from the coastlines in.  Across Northern New England, enough cold air is likely to hold on for a mostly snow event.  Skiers and snowmobilers, alike, should be getting excited for a dumping of white gold, and perfectly timed for Thursday night through Friday (not developing until Friday in Central and Eastern Maine), to deliver a beautiful new shipment of snow to the North Country just in time for the weekend with close to one foot in the mountains of Vermont, New Hampshire and Maine, and still over half a foot in the Lakes Region of NH, Interior Maine, and Southern VT.  In the Bangor area, there will be an extended period of sleet during the afternoon and evening - should temperatures aloft warm just a bit more than expected, this could fall as freezing rain instead and that would cause extensive power outages in this area...but for now sleet seems like the more dominant precipitation type.  Farther south, the situation becomes trickier during the day Friday.  It appears as though this storm center will pull enough warm air northward for snow to change to rain Friday morning, just as the most significant precipitation moves in across Central and Southern CT, RI, Southeastern and Coastal MA.  Farther inland, through the Merrimack Valley, Worcester Hills and Connecticut River Valley, cold air near the surface will be very hard to dislodge.  As a result, we're likely to find a few hours of sleet after the snow on Friday morning, lasting until Friday midday.  A couple of hours of steady freezing rain will be possible in the Route 2 corridor of Northern MA into the early afternoon, where this will put stress on powerlines and a few power outages will be possible, then finally a change to plain rain later Friday afternoon, with this change occurring by early afternoon farther east in the Merrimack Valley where less freezing rain will occur.  See accumulation maps below this discussion.  In total, nearly an inch of melted equivalent precipitation will fall through much of Southern New England on Friday.

While this storm will not be nearly as potent as our last system - owing largely to less northern energy feeding storm development - this one will still pack a punch.  As the storm moves from Central New Jersey Friday morning, to the Southern Maine Coastline by Friday evening, winds will gust along the coastlines and in Southeastern New England.  Expect easterly wind gusts to 40 mph during the first half of the day...then a quick wind shift to the southwest with gusts over 60 mph possible later Friday afternoon in Southeastern MA, Rhode Island and Southeast CT.  These winds would be enough not only to blow smaller objects around, but also to down a few tree limbs and perhaps cause some power outages.  It's very important to note that while these winds would be strong enough for some damage, they should not be nearly as strong as last Friday's storm.

Our storm center will continue to move northeast through Maine Friday night into Saturday morning...with snow ending in Central and Northern Maine during the day Saturday.  The remainder of New England, however, should be out enjoying the weekend, with a sunny sky on Saturday with high temperatures well into the 30's, and cirrus clouds filtering out the sunshine at times on Sunday, but temperatures still reaching close to the freezing mark.

A relatively weak northern stream disturbance at the jet stream level will pass over New England on Monday.  While it appears as though there won't be enough moisture to feed significant snows with this energy center, light snow is possible across most of New England through the day on Monday.

With a trough, or dip, in the jet stream lingering through the rest of the month, the cold weather pattern will continue right through the end of December!

Enjoy your Thursday,
Matt

Matt's Technical Meteorological Discussion:  Updated Thursday, December 15 at 1:45 PM

I've reviewed the 12Z NAM, GGEM and GFS and have decided to maintain my course for the time being.  That being said, let's start from the beginning.

As with last week's event, we're looking at an antecedent airmass that is cold, dense and stubborn.  In fact, this airmass is more dense and will be even more stubborn than last week's airmass, as the high to our north is only slowly retreating and this cold is well entrenched.  The result will be falling temps after sunset this evening, and those temps should continue to tumble until sometime around 10 PM - midnight when clouds thicken the blanket over NewEng and the surface winds begin to increase out of the east and northeast.  Dewpoints are running either side of zero across all of NewEng this afternoon and about the only thing that could erode that would be a prolonged 50 knot or stronger low level jet blasting into the heart of the cold all day tomorrow.  Of course, with the low center forecasted to pass from Central NJ to just off the coast of NH tomorrow, that's exactly what we'll be doing.

The end result is a burst of snow that moves north into NewEng overnight Thu night...and changing type to sleet and then rain quickly in far Southern NewEng.  We actually owe this arctic air a favor, as it looks like the dome of cold air stays thick enough to refreeze precip as sleet in most areas of the interior of Southern NewEng - and then later in the day for interior Maine - rather than allow freezing rain to fall.  Should there be more warm air aloft, we're looking at a crippling freezing rain event for the interior, and this is a high-stakes forecast.  I have acknowledged the potential of more widespread power outages for interior Maine should I be incorrect in my ptype forecast, and I am mentioning the possibility of a few outages along the Route 2 corridor of Northern MA, where I think an interesting mix sets up that may cause the most treacherous conditions out of what transpires in Southern NewEng.  The 850 temp forecasts have been fairly consistent among the guidance, and from run to run, over the past several model runs.  The precip timing has trended quicker in the 12Z runs and that's likely to be the case in reality as warm advection should be rather abrupt and well defined in the mid-levels.  This surge of warm and moist advection pre-dawn Friday should be accompanied by a burst of moderate to locally heavy snow.  Thereafter, I expect the cold air to hold tough at the surface, though warm air will have to win out aloft.  Additionally, strengthening southeast flow will erode cold dome from the edges first - Southern CT, RI, SE MA and coastal MA/NH during the morning.  See accumulation maps above for how much snow I'm thinking will fall before the changeover.  Ratios I used are low across the board, and across the north that's largely due to a seemingly inevitable mix with sleet for awhile.  Ratios in Southern NewEng with morning snow should range from 12:1 Merrimack Valley to 7:1 Hartford.  Across Northern NewEng, generally a 10:1 average overall...though a bit higher in the mountains where cold air can flex some more muscle.  As for thermal structure, I've basically stuck fairly close to the superior NAM's resolution...though even the NAM may be eroding surface cold air from Northern MA Route 2 corridor too quickly, and that's why after changing from snow to sleet in the morning...I'm going from sleet to freezing rain until mid-afternoon in this location.  Along the coast the onshore flow will allow snow to change to wet pasty snow...then eventually to rain by late morning or midday all the way into the coast of Maine, and this will limit amounts along coastlines.  Should be a rather sharp increase in snow amounts over interior SE NH as illustrated in the maps above, owing to the depth of the cold air and a weak coastal front that may set up inland in New Hampshire.  Still, I expect sleet to mix in for much of the day, and have limited ratios to about 5:1 in places like Concord by midday and afternoon.  As mentioned above, there is much concern for Interior Central and Eastern Maine just away from the surface coastal modification for freezing rain potential, but it looks just cold enough for sleet instead.  As for QPF amounts, I've shifted the maximum axis of .75-1.0" to the northwest of where the models are indicating just slightly, as this adjustment puts max amounts along and just to the left of the storm track, which makes sense synoptically given the thermal boundary that will set up to the left of the storm.

As the storm center moves to the NH/Srn ME coast, winds will swing around to the west and southwest in Southern NewEng and with cold advection around the belly of the low, winds will start to crank from the SW after having already gusted over 50 mph from the southeast on Cape Cod, in the mild and well-mixed layer that may exceed 50 degrees for an afternoon high!  In the wraparound cold advection, winds still may gust over 50 but from the opposite direction, and an isolated power outage is possible with these wind gusts.  Upslope snows may develop in the Berkshires with the wind shift and cold advection, though drier air moving in will help to squash them later Friday night.

Saturday looks quiet before Sunday yet another potent and moisture laden southern stream system shoot across the Southeast.  This time, flow is flat enough to keep the system south of us, though cirrus shield will move overhead on Sunday, helping to limit temperature rise in conjunction with colder low level air seeping south and east into NewEng.  By Monday, northern stream shortwave moving east over NewEng should bring clouds and light snow for most of the day.

Thereafter, I'm still concerned...as expressed earlier in the week...that next week, although featuring a trough in a favorable position to our west, also features a trough that's just too broad, and a pattern that will send several clippers to our south.  This would mean most of the week would be cold and dry with snow missing to the south, though any clipper that could intensify enough to close off a circulation would be able to tap Atlantic moisture and produce a moderate snowfall for us.  I don't see too much chance of that shaping up right now until at least later next week, if that.

We'll see.  That's all for today.

Matt

Cold and Dry Air Protects New England...Wintry Mess to End the Week

Welcome to the weather blog - a regular Monday through Friday discussion of the weather!  You'll find a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow. If no technical discussion is available when you check in during the morning, check back later as it often comes after the Weather Summary - I try to indicate at the end of the general weather summary when/if a technical discussion is coming. My email is contact@mattnoyes.net.  While the discussions usually will only come on days I'm working, I'll occasionally issue special updates when the weather warrants.  This blog is for you, so I hope you enjoy it!  -Matt Noyes

For latest radar imagery, to check for watches and warnings, and for links to sites in the world of weather, feel free to click over to my website: www.mattnoyes.net 

Matt's Weather Summary:  Our expansive dome of deep cold air will remain over New England for Wednesday, keeping us very cold, but also continuing to protect us by keeping the atmosphere relatively dry.  While New England enjoys another day of sunshine, temperatures will still be quite chilly though winds should be light.  Ocean effect snow showers will continue to fall across Cape Cod throughout the day Tuesday from the northern and eastern parts of Sandwich points east as the arctic air continues to spill across relatively warm waters of the Atlantic ocean.  Accumulations during the day should be light overall given shifting winds that will spray these snow bands across most of the Cape, though another inch or two is possible under the heaviest snow bands. 

But while New Englanders remain protected by our arctic dome, there is plenty of moisture...and plenty of disturbed weather to find across the nation.  Wednesday morning surface analysis shows our strong and cold high pressure center positioned just north of New York State, and a storm center moving east into Northern Minnesota.  The attendant cold front is draped southward from this storm center, through the Midwest, and to another developing low pressure center moving into Central Texas.  It's this area of low pressure that's been our focus for a potential end of week storm, and while it's still too early for exact details, here's how I'm thinking things will break down with this storm, and our own weather in New England:

After a mostly clear and frigid Wednesday night with temperatures either side of zero - below zero northern and western New England, single digits most other spots with deeper valleys back below zero, Thursday should start out with cold sunshine as our protective bubble of high pressure remains in charge.  Slowly, though, this protective airmass will begin to erode from the top down.  In it's place will come moisture...streaming up from the south in advance of the developing Southeastern U.S. storm center...and clouds will spill into New England high in the sky through the day on Thursday.  In the world of meteorology, these are called "cirrus" clouds, and indicate that moisture moving in aloft *may* indicate precipitation within 18 to 36 hours.  That rule should hold true in this instance.  These increasing Thursday clouds will temper just how much communities can warm up across New England, and average high temperatures will likely not make it to the freezing mark...holding in the upper 20's for most.

Thursday night, the southern storm center will have already gathered Gulf of Mexico moisture and will be shifting east toward the Eastern Seaboard.  Meanwhile, across the Upper Great Lakes and Upper Midwest, an energetic disturbance aloft in the atmosphere will be stalling out and spinning.  The counterclockwise flow of air around this disturbance will help to create a trough, or dip in the jet stream winds aloft that steer storm systems and act as a thermostat for the atmosphere - separating warm air to the south from cold air to the north.  This new jet stream configuration will mean the steering winds will be U-shaped...making a dip across the Ohio Valley where new disturbances will shoot east, and a flow from south to north along the Eastern Seaboard.  The end result of this pattern will be to pull the storm center off the Southeast Coast northward with its significant moisture feed from the Gulf of Mexico and the Atlantic, and for this storm to interact with a new bundle of upper level energy ejecting out of the Ohio Valley.  Once again, much like one week ago, we will watch as energy and moisture converge over New England.  The difference this time is that there is much less northern energy to work with, but moisture will still be plentiful - the overall result will be a less intense but still potent system.

As moisture continues to surge northward Thursday night, snow will develop for most of Southern and Western New England.  This cold air is quite dense, and will be difficult to move, but a persistent flow of warm air off the ocean, and warm air moving in aloft, will erode the cold from the coastlines in.  Across Northern New England and Western Massachusetts, enough cold air is likely to hold on for a mostly snow event.  Skiers and snowmobilers, alike, should be getting excited for a dumping of white gold, and perfectly timed for Thursday night through Friday (not developing until Friday in Central and Eastern Maine), to deliver a beautiful new shipment of snow to the North Country just in time for the weekend.  Farther south, the situation becomes trickier during the day Friday.  Right now, it appears as though this storm center will pull enough warm air northward for Thursday night snow to change to Friday rain just as the most significant precipitation moves in across Central and Southern CT, RI, Southeastern and Coastal MA.  The situation also appears to favor an all snow event with heavy snow falling across ski country, as mentioned above, where a foot of snow is a possibility.  The trickiest forecasting comes into play from Southeastern NH through the Merrimack Valley and into the Worcester Hills.  In this area, precipitation that begins as snow Thursday night will be very slow to changeover.  Though warm air will eventually work in aloft, which would favor a change to sleet or freezing rain by Friday afternoon, it's entirely possible that the bulk of the precipitation will fall as snow in these areas before the changeover, and we need to watch this possibility carefully for the potential of a significant heavy, wet snowfall accumulation Thursday night through Friday early afternoon.  This cold air is dense and means business, so we certainly don't want to underestimate its staying power.

This storm will continue to move northeast through New England across Maine Friday night into Saturday...with snow ending in Central and Northern Maine during the day Saturday.  The remainder of New England, however, should be out enjoying the weekend, with Saturday and Sunday both looking like a blend of sun and clouds, with highs in the 30's Saturday and near 30 Sunday.

The cold weather pattern will continue through the end of December!

Technical Discussion:  A big day, I know, but a charity event has me on the road.  Please reference the archives (at left) to read yesterday's technical thoughts.  Should have time for a pre-storm techie write-up Thursday.

Happy Hump Day,
Matt

Frigid Midweek...Wintry Mess for End of Week

Welcome to the weather blog - a regular Monday through Friday discussion of the weather!  You'll find a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow. If no technical discussion is available when you check in during the morning, check back later as it often comes after the Weather Summary - I try to indicate at the end of the general weather summary when/if a technical discussion is coming. My email is contact@mattnoyes.net.  While the discussions usually will only come on days I'm working, I'll occasionally issue special updates when the weather warrants.  This blog is for you, so I hope you enjoy it!  -Matt Noyes

For latest radar imagery, to check for watches and warnings, and for links to sites in the world of weather, feel free to click over to my website: www.mattnoyes.net

Matt's Weather Summary:  Our Tuesday begins with some rather unexpected snow showers along the Maine coastline in association with a slow-moving mid-level atmospheric disturbance - and some of these have dropped a half inch of snow per hour at times in localized bands of snow.  Farther south, flurries and snow showers have grazed Eastern Massachusetts and will be progressive, with sunshine breaking through the clouds during the day Tuesday for most of New England.  Our surface analysis Tuesday morning features a cold dome of Canadian high pressure just north of New England - air that brought weekend high temperatures just barely above zero for our neighbors to the north moving in, holding Tuesday's high temperatures for New England only in the teens!  The saving grace with this airmass is that the air dry, as well as cold, so plenty of sunshine will be out for the interior - and should eventually win over the clouds in Eastern New England.  Those of you with a window in your office, or who drive frequently during the day, will be able to soak up some rays, though those of you who work outdoors or like to walk to lunch will want to bundle up.  In addition to the chilly air, winds will be active, adn though they won't be all that fierce, even a breezy day of wind gusts over 20 mph at times will add an extra bite to the air!  It's important to note that there will be exceptions to the dry conditions, found downwind of our large bodies of relatively warm water.  South of Lake Champlain, VT, lake effect snow showers continue to stream southward through southwest Chittenden and Western Addison counties, where a fresh couple of inches of snow will fall under this localized snowband.  Another area of snow showers will set up downwind of Massachusetts Bay, over the Outer Cape.  Here, one round of snow showers and squalls moves through Tuesday morning, then a spray of snow showers will be the rule Tuesday afternoon.  I expect to find more organized bands of snow showers developing Tuesday evening and lasting through Tuesday night, with perhaps either side of 3-4 inches of fresh snow in highly localized communities under a better organized snowband Tuesday night.  While placement of these bands can be tricky, my best assessment would be a couple of inches on the Western Tip of P'Town, closer to 4 inches in Brewster, Dennis and Yarmouth, and a couple of inches in Central and Western Nantucket overnight Tuesday night.  Again, if the band sets up just a bit differently, these highest amounts would fall either side of my estimate.  With winds subsiding and skies remaining mostly clear for the rest of New England Tuesday night, expect a downright frigid night, with temperatures below zero for most of the northern half of New England, and not much above it in southern areas!

This expansive dome of deep cold air will remain over New England on Wednesday, but will continue to protect us by keeping the atmosphere relatively dry.  While New England enjoys another day of sunshine, temperatures will still be quite chilly though winds should be light.  But our quiet and cold corner of the nation doesn't tell the story on the bigger picture.  By late Tuesday into Wednesday, a strong, energetic upper level disturbance will be dropping south into the Rockies and Intermountain Region from the North Pacific.  This disturbance, driven by the jet stream winds aloft that steer storm systems and act as a thermostat for the atmosphere - separating cold air to the north from warm to the south - will spawn a series of weak storm centers along the spine of the Rockies and into the Oklahoma Panhandle.  These multiple waves of low pressure will eventually evolve as two separate entities - one low pressure center that will lift into the Northern Tier of the U.S., and another that will run along the Gulf of Mexico coastline.  This southern storm center will be especially important to watch, as it will - like last week's system - pick up plenty of moisture from the Gulf of Mexico.  By Thursday, this storm center will begin to turn northward in preparation for a run up the Eastern Seaboard.

With such a solid dome of cold air in place for mid-week, one would think the question of rain or snow should be an easy one if and when this storm center arrives later Thursday into Friday.  But of course, the weather scenario in New England is seldom an easy one to negotiate, especially with ocean water temperatures running in the 40's off our coastline, and with a slug of warm air that will be carried northward from the Gulf of Mexico along with the moisture.  At this point, it looks like precipitation would perhaps start as snow Thursday night, then go to sleet and freezing rain for locales through the interior of Central and Southern New England, rain in some areas close enough to the coast to feel the effects of the warmer waters (perhaps penetrating farther inland than last time) and ski country could see a dumping of snow.  But with some time between now and then, the details will likely become much more clear over the next couple of days.

BUNDLE UP!

Technical Discussion:  Out By Early Afternoon.

Matt

Matt's Technical Meteorological Discussion:  Updated Tuesday, December 13 at 1:25 PM

Surprise!  Never a good word to hear in a forecast discussion, but they can and do happen, and that was the case this morning along the Maine coastline, at least for this forecaster.  Slow moving but well defined mid-level vorticity maximum stalled off Maine coastline and kept warm advection going for a couple of inches of coastal Maine snow.  Farther south, flurries in the Boston and Portsmouth areas were transient as the cold air wrapped around behind aforementioned circulation in the mid-levels.

Rest of the day our dry air continues to rule the roost with mesoscale exceptions.  Snow showers along Maine coast slowly move east and clouds already breaking up but should be more noticeably diminished by mid-afternoon.  Lake Champlain snow showers have fallen apart.  Cape Cod ocean effect snowbands look to be on target thus far from yesterday's thoughts and I don't see much reason to change the forecast.  Ocean induced CAPE goes over 500 J/kg  but as mentioned yesterday, inversion is pretty low at about 880 mb.  Wind flow will back slightly this evening and that should still set up an OES band for Western P'Town, Brewster, Dennis, Harwich and Yarmouth.  Wind slowly veers toward the north again late tonight and this may swing band slowly westward so Barnstable likely to get in on some of the higer accums as well.  At this point, I'm still thinking 3-4" in the higher amounts, with 2" either side.  Snow showers have been ongoing on South Shore of MA...though as winds back later today I expect those to move offshore, then come back a bit toward dawn Wednesday.  Elsewhere, temps will fall below zero in any low lying areas north of the MA state line, and in deeper valleys of Southern NewEng, with most other areas in the single digits overnight Tuesday night, excepting the urban centers.

Expansive area of high pressure and associated subsidence holds in both the dry and the cold on Wednesday.  With an even colder start Wednesday morning than Tuesday, it'll be hard to rebound too much above Tuesday's values...perhaps by a few degrees but that should be it.  Snow showers will continue on the Outer Cape through Wednesday with some additional accumulation possible.

Thursday starts sunny and cold, and ends with increasing clouds ahead of southern system sneaking up the Eastern Seaboard.  I haven't gone as warm as statistical guidance for Thursday afternoon, largely because surface ridge axis still moving through and mixing should be limited under dome of subsidence.  Some snow may break out in Southern NewEng Thu night though warm air will be rushing in at 850 mb.  At the surface, however, cold dome will be dense and difficult to dislodge.  This should send the low pressure center heading somewhere over Southeastern NewEng on Friday, which will allow Eastern areas to change to rain.  Farther inland, though, cold air will not dislodge as quickly as even the high-resolution NAM suggests it will, and freezing rain will be a significant concern especially in the Monadnock Region, and Northern MA along the Route 2 corridor outside of 495.  Enough moisture streaming northward for close to 1.0" QPF...as one maximum axis will be along the Appalachians, and the second max will come along midlevel thermal boundary draped SW to NE across NewEng on Friday.  Not time to sound the alarms on a major ice event yet, though...still lots that can change and I'm also not ready to give up on a colder and therefore slightly farther SE solution given density of this very impressive arctic airmass.  Farther north, cold air will hang on aloft and at surface for mainly snow event in Northern VT, White Mountains and Mountains of Maine...skier's delight.

Thereafter, another arctic front will push southward on Saturday...not making it into New England until late...so many areas should be able to warm into the 30's with a stiffening wind.  This front does plow through for a much colder Sunday, and thereafter, the North Atlantic Oscillation is forecasted to be weakly to moderately negative but while the trough position is good, the trough is a bit broad and the possibility exists that we will sit from this weekend to Christmas in a pattern that features very cold air, but with regard to snow, we end up waiting for a clipper to amplify enough on its way by to our south to develop enough of a circulation to pull in Atlantic moisture.

We'll see...that's all for today.

Matt

Cold Air to Take Centerstage...Another Wintry Mix Late This Week

Welcome to the weather blog - a regular Monday through Friday discussion of the weather!  You'll find a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow. If no technical discussion is available when you check in during the morning, check back later as it often comes after the Weather Summary - I try to indicate at the end of the general weather summary when/if a technical discussion is coming. My email is contact@mattnoyes.net.  While the discussions usually will only come on days I'm working, I'll occasionally issue special updates when the weather warrants.  This blog is for you, so I hope you enjoy it!  -Matt Noyes

For latest radar imagery, to check for watches and warnings, and for links to sites in the world of weather, feel free to click over to my website: www.mattnoyes.net 

Matt's Weather Summary:  A quick note right off the bat - thank you to all those of you who not only utilized this blog, but also to the hundreds of you who wrote to me with observations, comments and with your support both during and after the storm on Friday.  I've been trying to get back to everyone personally, but if I somehow miss you in my replies, know that your correspondence still means just as much to me.  I was thrilled to see how involved everyone was through my personal email, and it meant a great deal to me that some of you even voiced your support through NECN's feedback section as well.  I am truly blessed to have such a wonderful and supportive group of viewers, and I'm thrilled that so many of you are finding this site useful on a daily basis for your forecast.  I look forward to word of the site and our NECN broadcasts spreading and finding more of you each day.

Now onto the weather, where more challenges will await this week.  The first half of the week will feature relatively quiet weather, but cold temperatures will take center stage.  Let me set the scene:  Monday morning surface analysis features a weak area of low pressure chugging eastward over Northern New York State.  This weak storm center is dragging a cold front east with it, and this front is the separator between our air - which was in the 30's and even over 40 in a few spots this weekend - and air producing morning low temperatures well below zero and afternoon highs only in the single digits across Ontario.  As this cold front pushes into New England on Monday, lots of clouds will stick around Northern and Western New England, with a few snow showers continuing in the mountains where "upslope flow" continues - that is, a westerly wind direction pushing air up against the mountains, forcing the air to rise and create clouds and precipitation.  For the rest of New England, while there will be plenty of moisture for some puffy "cumulus" clouds today, the atmosphere should be able to stir up enough to keep plenty of sunshine in the mix, as well.  Temperatures will respond to this sunshine and the seasonable airmass sitting over us.

As the cold front pushes through New England Monday afternoon, winds swing around from the northwest and cold air filters south and east.  Far northern areas like Burlington, VT, will actually cool later this afternoon, while the rest of New England find cold air noticeably spilling in overnight Monday Night.  This air will be cold enough in contrast to the relatively warm waters of Lake Champlain, in northern Vermont, to spawn lake effect snow showers south-southeast of the Lake, in the suburbs south of Burlington.  These snow showers may crank out a couple of fresh inches of snow in the higher terrain south of the lake that falls under this band of snow showers Monday night into Tuesday morning.

Tuesday features a cold dome of Canadian high pressure building into New England - air that brought weekend high temperatures just barely above zero for our neighbors to the north will move in, holding Tuesday's high temperatures for New England only in the teens!  There will be two saving graces with this airmass: 1) With the air dry, as well as cold, plenty of sunshine will be out and those of you with a window in your office, or who drive frequently during the day, will be able to soak up some rays, and 2) With the center of high pressure nearby, winds won't be terribly gusty, but still will be a bit breezy, and that certainly will add an extra bite to the air!  It's important to note that - as with Monday night's Lake Champlain snow showers - there will be an exception to the dry conditions, and that will be downwind of Massachusetts Bay, over the Outer Cape.  Here, I expect to find bands of snow showers developing Tuesday evening and lasting through Tuesday night, with perhaps a couple of fresh inches of snow in highly localized communities under these bands over the Outer Cape - though I will examine this more closely on Tuesday.  With winds subsiding and skies remaining mostly clear Tuesday night, expect a downright frigid night, with temperatures below zero for most of the northern half of New England, and not much above it in southern areas!

This expansive dome of deep cold air will remain over New England on Wednesday, but will continue to protect us by keeping the atmosphere relatively dry.  While New England enjoys another day of sunshine, temperatures will still be quite chilly though winds should be light.  But our quiet and cold corner of the nation doesn't tell the story on the bigger picture.  By late Tuesday into Wednesday, a strong, energetic upper level disturbance will be dropping south into the Rockies and Intermountain Region from the North Pacific.  This disturbance, driven by the jet stream winds aloft that steer storm systems and act as a thermostat for the atmosphere - separating cold air to the north from warm to the south - will spawn a series of weak storm centers along the spine of the Rockies and into the Oklahoma Panhandle.  These multiple waves of low pressure will eventually converge as two separate entities - one low pressure center that will lift into the Northern Tier of the U.S., and another that will run along the Gulf of Mexico coastline.  This southern storm center will be especially important to watch, as it will - like last week's system - pick up plenty of moisture from the Gulf of Mexico.  By Thursday, this storm center will begin to turn northward in preparation for a run up the Eastern Seaboard.

With such a solid dome of cold air in place for mid-week, one would think the question of rain or snow should be an easy one if and when this storm center arrives later Thursday into Friday.  But of course, the weather scenario in New England is seldom an easy one to negotiate, especially with ocean water temperatures running in the 40's off our coastline.  At this point, it looks like precipitation would perhaps start as snow, then go to rain in some areas close enough to the coast to feel the effects of the warmer waters (perhaps penetrating farther inland than last time) and ski country could see a dumping of snow.  But, keep in mind that this is still 4-5 days out, and right now it's silly to make much conjecture on where a rain/snow line would fall.  Bottom line is that we have another chance of a moisture laden storm marching up the coastline at the end of this week, and until then, frigid air will be showcased in New England for midweek!

Enjoy your relatively mild day today!

Until tomorrow,

Matt

Matt's Technical Meteorological Discussion:  Updated Monday, December 12 at 1:05 PM

Arctic front seems innocent but is packing a punch this morning as it moves southward.  Temps will hold steady or fall this afternoon as slug of air in the single digits pours southward across the Canadian border.  Front is marked by a wind shift to the northwest, and winds ahead of boundary are backing nicely to illustrate frontal passage.  Ambient RH low enough to avoid problems with snow showers/squalls except where orography assists in the mountains of Northern and Western NewEng, though RH high enough to keep lots of clouds in place where they are until what little mixing there will be can eat away at the layer.  Lake effect snow band will crank later today off Lake Ontario and this will likely carry snow showers all the way into Northwest CT this evening.  Elsewhere, skies will gradually clear thru the overnight and as temps fall to the single digits thru most of interior NewEng and teens in most of the eastern urban centers, the only thing keeping the temps up will be an active cold air advecting boundary layer wind.  This cold air will set up enough difference with the Lake Champlain water for lake effect snow showers on a wind at 350 degrees in VT.  This should dump snow showers overnight Monday night into Tuesday morning over Vergennes, western parts of Charlotte, and the surrounding communities located south-southwest of Lake Champlain.

The cold continues to pour in for the first part of Tuesday, and low level thickness values match up well with surface max temps in the teens for just about all of NewEng.  NW wind likely to help with a bit of downsloping so places like Boston and Providence can eclipse 20, but most spots under that mark, and no matter how you cut it, feeling will be cold for the public.  One saving grace is the sunshine in most areas, and the other is that the wind won't be ripping - only about 10-15 kts for most areas, but that's still enough to add some further bite to the arctic air.  The sunshine, of course, comes courtesy of the dry nature of this air, but once again we'll see a large delta T (temperature difference) from ocean to air across Massachusetts Bay, and with a wind still at about 350, this would bring ocean effect snow bands over Dennis and Brewster on Cape Cod.  There are a couple of tricks here:  1) Determining whether we're going to be dealing with a single or multi-band event, and 2) exactly when it sets up and how intense it becomes.  Let's deal with the second question first - timing and intensity.  The air pouring over the ocean waters is cold enough for ocean effect bands to begin Tuesday afternoon, though it's often very difficult to generate efficient lake (ocean) effect bands with strong cold advection occurring during daytime heating - the combination of broadscale subsidence associated with cold advection teams with the mixing effects of diurnal heating and keeps activity rather disorganized, though a spray of snow showers with heavier bursts should still be present across the Outer Cape.  Tuesday evening I'd expect to find more organization, and it will be overnight Tuesday night that the most efficient snow production takes place.  At this point, the NAM is not keying in on a productive event, and the reason for this is likely two-fold: 1) An inversion at about 880 mb, low for healthy tops to develop with the ocean effect clouds, and 2) Fast wind speeds at 925 mb limiting the amount of time air spends over the ocean waters.  As for the first question of multiple or single banded event, the tendency is usually for multi-banding over Cape Cod, but this event may exhibit a dominant band that, in effect, would make this behave as a single band event.  At 00Z, there is still some backing of the flow from surface to 850 mb, but by 06Z, all low level wind has come around nicely to a 350-360 trajectory.  This eliminates directional shear, and speed through the lower levels lines up around 20-25 kts.  Additionally, boundary layer forecasts indicate a friction enhanced surface convergence zone between a 330 flow off the land, and a 350-360 flow over the water.  This should encourage single band development overnight Tuesday night, and will enhance convergence in the band.  With ocean induced CAPE over 500 J/kg, this should further fuel convective development within the convergence band.  This single band is likely to be flanked by a few other smaller bands that will bring much less impact.  Given the trajectory, the multibanding event should affect everywhere from Barnstable eastward, with the better organized band overnight Tuesday night focused from Yarmouth to Brewster.  As for accumulations, top of the lift will be in dendritic crystal growth layer...favorable for high ratios...and as always the challenge here will be trying to predict QPF which will not be modeled well by the guidance.  At this point, I would think 3"-4" Barstable/Yarmouth/Dennis - I would go higher but I want to see the NAM and SUNY SB MM5 in particular get a better handle on this with regard to inversion height and upward vertical motion.  For now, SUNY SB MM5 putting out about .10" which is probably going to be only slightly underdone but ratios should be high.

As for the Thursday situation:  Have to run for administrative stuff so will be very brief on thoughts here.  1) Too early to determine rain and snow line for sure, 2) High in place is very cold and dense which means it will hard to dislodge - this means snow to start most areas then the ocean air has to do its job chipping away at the edges.  3) Storm track should not be taken as literal among the models...they never handle the density and stubborness of cold well enough and the storm track is likely to be farther east...or south and east...than progged.  4) Good dumping of snow for someone - if the models are right it's ski country but again, let's keep the jury out on this one.  Bottom line is I'm not going to get the public up in arms for a potential blast...nor am I going to say this looks like more rain or weaker than the last storm.

More tomorrow.  Gotta run.

Matt

Storm To Be Remembered For Ferocious Intensity...Though Not for Duration

Welcome to the weather blog - a regular Monday through Friday discussion of the weather!  You'll find a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow. If no technical discussion is available when you check in during the morning, check back later as it often comes after the Weather Summary - I try to indicate at the end of the general weather summary when/if a technical discussion is coming. My email is contact@mattnoyes.net.  While the discussions usually will only come on days I'm working, I'll occasionally issue special updates when the weather warrants.  This blog is for you, so I hope you enjoy it!  -Matt Noyes

For latest radar imagery, to check for watches and warnings, and for links to sites in the world of weather, feel free to click over to my website: www.mattnoyes.net 

Matt's Weather Summary:  Wanted to get this out before we go to live continuous storm coverage on NECN beginning at 11 AM - feel free to tune in if you can for updates.

Snow that's falling fast and furious this Friday morning piles up quickly through the day, before drawing to a close this evening.  A morning surface analysis shows one area of low pressure over the Carolinas handing over its moisture to a developing area of low pressure off the New Jersey coastline.  This new low pressure center will be the dominant storm center that will help to feed both tropical moisture from the south, and Atlantic moisture from the east, into New England as a strong energetic disturbance moves in from the west.  The convergence of this moisture and energy will feed our developing storm passing south of New England, and continuing to bring bands of extremely heavy snow to the area.  With so much moisture and energy converging on New England, snowfall rates of 1-2" per hour will be common and 2-3" or even 4" per hour will be possible in a few locales - extremely rare for Southern New England.  This will pose problems on our roadways throughout the day.  With a persistent onshore flow from ocean waters running temperatures in the middle 40's, a powerful coastal frontal boundary will continue to establish in New England, keeping amounts down but winds up on the warm side, near the ocean, and keeping snowfall totals higher with a fluffier snow farther inland.

This storm will likely pass immediately south of New England, and while the storm is quick-hitting, the intensity of the snow will likely be high enough to deliver a foot or more of snow to interior Eastern and Central Massachusetts, Northeast CT, Northern RI and extreme Southeast NH.  As you head closer to the coastline, amounts will fall off dramatically on the warm side of that coastal front from Boston southward.  I wouldn't be surprised to see Logan Airport and immediate coastal locales on the South Shore of MA only picking up about 2-5" of wet sloppy snow, while Cape Cod and the Islands may get an inch or two before a changeover to sleet and then rain.  Please refer to my maps below by clicking on the thumbnails, but it's important to note a few things when viewing them:  1) I may change the forecast and not have time to update the maps.  2) If that happens, it's important to refer to this discussion (updates always appear at the top of the discussion) or to my broadcasts on NECN.  3) There is a VERY sharp cutoff around the South Shore of MA and this means if you live near the sharp cutoff you should be prepared to fall either side of the amounts.

I'd expect snow to taper by mid-afternoon in Western New England, and late afternoon to evening in eastern areas.  Behind the storm this weekend, somewhat milder air will actually move into our region from the southwest.  It's important to note that while this means temperatures are likely to rebound into the middle 30's, and that will feel good to the body after a cold stretch, those numbers are still below normal for this time of the year.  Saturday looks mostly sunny with a break between systems, but by Sunday a gentle feed of warmth and moisture aloft will mean clouds fill in across New England with most areas seeing more clouds than sun overall, and scattered showers of rain and snow by Sunday afternoon.  Later Sunday, a slow moving cold front will make an approach toward New England.  At the same time, yet another wave of low pressure will emerge out of the Gulf of Mexico and Southeastern US, and this storm system will develop as it moves northward along the front.  At this point, it looks like most of New England won't have to worry about this storm as it moves east of us Sunday Night into Monday, but Eastern Maine will need to keep a close eye on this later Sunday into Monday.  The remainder of the area should start the week quiet and relatively dry.

Overall, however, I still expect the cold and wintry pattern to prevail for the next couple of weeks, which keeps our chances for a White Christmas quite high in many parts of New England!

Stay safe on this Friday - have a great weekend.

Matt

Significant Snow Threat for Southern New England...Quiet Thursday to Prepare...Milder Weekend In Store

Welcome to the weather blog - a regular Monday through Friday discussion of the weather!  You'll find a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow. If no technical discussion is available when you check in during the morning, check back later as it often comes after the Weather Summary - I try to indicate at the end of the general weather summary when/if a technical discussion is coming. My email is contact@mattnoyes.net.  While the discussions usually will only come on days I'm working, I'll occasionally issue special updates when the weather warrants.  This blog is for you, so I hope you enjoy it!  -Matt Noyes

For latest radar imagery, to check for watches and warnings, and for links to sites in the world of weather, feel free to click over to my website: www.mattnoyes.net

Matt's Weather Summary:  A frigid start to our Thursday morning in conjunction with a bubble of high pressure - a fair weather center - that broke off of the cold arctic high that's been delivering record cold temperatures to the Northern Plains for several days now.  As this high pressure center moves to our south, cold air will stay locked in place through Thursday, though winds will diminish somewhat as the day wears on.  This dome of cold and dry arctic air will protect New England through the day, holding moisture at bay and allowing only a few high altitude cirrus clouds later Thursday afternoon to dim the sun.

Clouds will thicken Thursday night as temperatures fall into the teens and 20's for most areas...plenty cold enough to support snow as our arctic airmass will remain locked in place.  Meanwhile, to our south and west, two impressive storm centers will be moving toward the Eastern Seaboard and beginning to interact.  The first of these storms is a strong energy center in the upper levels of the atmosphere that will move east from the Ohio Valley on Thursday.  Precipitation has been limited with this disturbance due to a lack of moisture - largely thanks to the expansive and dominating cold high pressure center mentioned above - but more snow will develop with this system as it taps moisture from a system to its south.  This second southern system is a weaker storm taking shape in the Northern Gulf of Mexico - on the southern periphery of the large high pressure center - and this storm will tap loads of Gulf moisture as it develops over the warm waters and humid air.  Our problem will come as these two storms begin to interact Thursday night, resulting in a moist and energetic storm center developing off the Eastern Seaboard.

This coastal storm will charge northeast, propelled by the fast jet stream winds aloft, and will have some similarities - and some big differences - from our previous storm (or lack thereof).  The similarities will focus on a storm track that moves south of New England, and a similar merger of a northern stream, cold, energetic disturbance with a southern stream system containing lots of moisture, and there is always inherent uncertainty on just how quickly and coherently two storms will merge.  And that brings us to the differences from the previous storm:  1)  The merger of these two systems will happen sooner than it did last time, which means the storm will be better developed when it passes south of us.  2)  This storm will tap more moisture from the Gulf of Mexico, since the southern stream half of it actually will originate in the Gulf, and this means the consequences of a hit would be much higher.  3)  Instead of a wind from the north, battling the advancement of moisture from the south, the clockwise flow around an area of departing high pressure will allow winds to turn from the south and help to carry moisture northward.  The bottom line of all this is that a logical and objective analysis of the event tells us there's much more to work with for storm development here, and plowable snow is likely to reach much farther north.  Finally, it looks as though the precipitation shield would not cut off as quickly on the north side this time around, a rain/snow line may come into play, and a coastal front will establish (warm air on the east of it, cool air on the west, and a band of enhanced snow in the middle), limiting amounts at the immediate coast from Boston southward, and resulting in higher amounts just inland.

Here's how it all should play out:  The storm center, as it moves northeast from the Mid-Atlantic coast Thursday night will spread snow into Western New England either side of 5 AM and into Eastern New England either side of 7 AM.  The snow will become heavier only a couple of hours after developing, and the center of low pressure will pass southeast of New England - passing over "benchmark", or 40 degrees latitude north, 70 degrees longitude west.  The reason this location is called "benchmark" in the world of meteorology is because this is the benchmark for significant winter storms to affect New England.  As the storm moves over this location, snows will fall heavily at times from mid-morning to mid-afternoon across especially Southern New England, where 1-2" per hour snows are possible!  So, while the storm is quick-hitting, the intensity of the snow will likely be high enough to deliver a foot or more of snow to interior Eastern and Central Massachusetts, Northeast CT, Northern RI and extreme Southeast NH.  As you head closer to the coastline, amounts will fall off dramatically on the warm side of that coastal front from Boston southward.  I wouldn't be surprised to see Logan Airport and immediate coastal locales on the South Shore of MA only picking up about 3-5" of wet sloppy snow, while Cape Cod and the Islands may get an inch or two before a changeover to sleet and then rain.  The north shore of MA, though close to the coast, will be far enough north to find colder temperatures and amounts still may near one foot.  Farther north and west, amounts will drop off more gradually then they will at the Southern coastlines.  For example, Springfield, MA, should still pick up about 9", 7" in the Berkshires, 8" in Concord, NH, around a foot in Portsmouth, 6" in Portland, ME, 3" in Bangor, 3" in Burlington, VT, 7" in Springfield, VT, about a foot in Hartford, CT, and Providence, RI, with lesser amounts as you head to the South Coast of New England.  It's hard to convey this with text, so please refer to my maps below by clicking on the thumbnails, but it's important to note a few things when viewing them:  1) I may change the forecast and not have time to update the maps.  2) If that happens, it's important to refer to this discussion (updates always appear at the top of the discussion) or to my broadcasts on NECN.  3) There is a VERY sharp cutoff around the South Shore of MA and this means if you live near the sharp cutoff you should be prepared to fall either side of the amounts.

I'd expect snow to taper by mid-afternoon in Western New England, and late afternoon to evening in eastern areas.  Behind the storm this weekend, somewhat milder air will actually move into our region from the southwest.  It's important to note that while this means temperatures are likely to rebound into the middle 30's, and that will feel good to the body after a cold stretch, those numbers are still below normal for this time of the year.  Saturday looks mostly sunny with a break between systems, but by Sunday a gentle feed of warmth and moisture aloft will mean clouds fill in across New England with most areas seeing more clouds than sun overall, and scattered showers of rain and snow by Sunday afternoon.  Later Sunday, a slow moving cold front will make an approach toward New England.  At the same time, yet another wave of low pressure will emerge out of the Gulf of Mexico and Southeastern US, and this storm system will develop as it moves northward along the front.  At this point, it looks like most of New England won't have to worry about this storm as it moves east of us Sunday Night into Monday, but Eastern New England will need to keep a close eye on this, and I actually do think there's a chance for snow in Central and Eastern Maine later Sunday into Monday.

Overall, however, I still expect the cold and wintry pattern to prevail for the next couple of weeks, which keeps our chances for a White Christmas quite high in many parts of New England!

Good luck with your snow preps on this Thursday.

Matt

Matt's Technical Meteorological Discussion:  Updated Thursday, December 8 at 2:07 PM

Ocean effect snow showers this morning around P'Town have since been squelched by lowering subsidence inversion building in courtesy of surface ridge axis moving steadily eastward.  With this ridge not passing through until this evening, no warm advection will take place and no airmass modification will occur, especially given very little mixing of this cold dense airmass with the subsidence moving through.  By this evening, cirrus should begin to spread in, but temperature will still be allowed to fall with dewpoints still running only in the single digits all the way to the South Coast (this will be important in our forecast).  Should already be in the teens north and 20's south this evening, though temp falls in Southern NewEng likely to be halted as winds gradually increase from the south.

Moisture will make steady progress northeast overnight Thursday night with lowering and thickening clouds.  At this point, I'm expecting snow to arrive in western areas around 5 AM and eastern areas by 7 AM - not impossible that it arrives sooner with warm advection underway, but no well defined vort lobe to touch it off.  One could also make a case for later arrival given dry air that may evaporate leading edge, but warm advection seems too strong for that.  So, Goldilocks would say this time frame is just right and that's where I've left it.

Lots of factors to play into this storm tomorrow.  Those of you who read regularly were appraised of my overall thoughts a couple of days ago, updated yesterday, and today I will continue to update my thoughts, rather than rehash everything - but you're always welcome to go back through the archives at left.

Initial snow under warm advection may be on the light side the first half of Friday morning, but snow should fall in earnest from mid-morning to mid-afternoon.  During this time frame, upward vertical motion goes through the roof as warm advection is maximized to the north of the new developing low and mid-level centers.  New low should develop off Central NJ coastline early Friday and will be a fast mover as it moves NE and crosses almost directly over benchmark during the day Friday.  While the system is indeed progressive, there are two tremendously impressive facets to it: one is the energy and the other is the moisture.  The vorticity maximum moving east is closing off as it moves out of the Eastern Great Lakes, and while it is neutrally tilted, it's packing over 30 units of absolute vorticity, and this would be enough to generate whiteout conditions on its own!  Add to this a steady stream of Pacific, Gulf and eventually Atlantic moisture, and 1-2" per hour snows are certainly well within reason from mid-morning to mid-afternoon.  I still think the NAM is too wound up and too far north, but the GFS has been underdone on QPF amounts and has just now caught up in the 12Z run.  No model is accurately placing the precipitation shield for Friday - a benchmark storm will produce the heaviest swath of precip either side of the MA Turnpike.  Additionally, the cold and dry arctic air in place today is a huge factor.  The ocean temps are in the mid 40's and this is something I've discussed at length in these discussions regarding previous events.  I do believe the warm ocean is going to play a significant role again in this storm, but with varying results.  Along the Cape and Islands this warm air should allow for a changeover to rain during the morning.  Along the South Coast of Massachusetts, ratios should be quite low...especially from midday onward as the onshore flow really has a chance to do its dirty work and we mix with rain at immediate coastal locales.  This will result in a coastal front developing inland about 20 miles from the South Coast of MA, and it could be a rather fierce front, too, with dewpoints this afternoon running in the single digits.  This is some dense, dry, cold arctic air and it's going to be very difficult to dislodge the airmass, so instead I'd expect a strong coastal front to develop, with heavy snow falling on the cold side of this frontal boundary, especially given the lift already present that was described above.  The combination of this low level forcing with upper level dynamic forcing could bring bands of snow exceeding 2" per hour to interior Eastern MA, and the atmosphere is unstable enough for moist slantwise convection to form in this strongly frontogenetic environment.  The result should be a relatively short-lived storm, but also a very intense one, and that's my reasoning for going with 12"+ for most of interior Southern NewEng (see maps above).  I went with this from the very first map early this morning, because I saw good agreement among the models on a solid 1" of QPF - and then I adjusted the placement based on the synoptic solution of a benchmark low discussed here the past couple of days.  Truth be told, I wanted to go 12-18" but I knew the public would focus only on the 18, and when most areas were below that, the complaints would come rolling in.  Again, the idea here is that the remarkable combo of low level and upper level dynamics should offset the short duration of the storm, and this could be remembered as one of the most intense, short storms to hit Southern New England in recent memory.

While amounts will diminish dramatically at the coastline, they will drop off more gradually as one heads north and west, and this comes thanks to southerly warm advection flow thrusting moisture northward, unlike last storm where northerly dry flow really ate up the snow for most of NewEng.

Winds should be gusty on the warm side of the coastal front but negligible on the cold side.  The north shore and Cape Ann is a tricky location due to the combination of cold arctic air and the battle with an onshore flow, and I have to think that immediate coastal locales will be limited on how much then can accumulate for the North Shore through Marblehead and Swampscott, though probably what we'll see are a few slushy inches at the coast and the north side of those towns will pick up closer to 8 or 9.  Immediate coastal locales by Newburyport may stay lower, too, but come inland by just a mile or two from the coast and I think that's as far as the coastal front can penetrate given the arctic dome, so the majority of the population in these areas sees the higher amounts.

Not many changes to the weekend though we still need to watch the Sunday night into Monday system for all of Eastern NewEng and especially for Central and Eastern Maine.

I'm not sure how much time I'll have to post a technical discussion tomorrow - if this thing turns out as I'm expecting, probably not much, so in case this is the last techie discussion for the week...have a great weekend.  Of course, if I bust on my forecast I'll have plenty of time to write...

Later,

Matt

Arctic Front Moves Through Wednesday...Cold and Dry Thursday...Snow En Route Friday AM

Welcome to the weather blog - a regular Monday through Friday discussion of the weather!  You'll find a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow. If no technical discussion is available when you check in during the morning, check back later as it often comes after the Weather Summary - I try to indicate at the end of the general weather summary when/if a technical discussion is coming. My email is contact@mattnoyes.net.  While the discussions usually will only come on days I'm working, I'll occasionally issue special updates when the weather warrants.  This blog is for you, so I hope you enjoy it!  -Matt Noyes

For latest radar imagery, to check for watches and warnings, and for links to sites in the world of weather, feel free to click over to my website: www.mattnoyes.net 

Matt's Weather Summary: 

5 PM Update:  In case you missed the noon show today, I did end up defining who I believe is likely to receive plowable snow on Friday - and that includes areas from extreme Southern VT, through most of Southern NH, points southward.  There is likely to be a mix with or change to rain on the South Coast and Cape Cod, and this will keep amounts down in these areas.  Farther north...plowable snow is still possible but those of you who watch and read regularly know I don't like to put something out there for exact numbers until I truly believe it is the best forecast.  I expect to have an accumulation map out in tomorrow morning's shows.  In the meantime, this guidance I've given above should help those of you in snow removal to plan accordingly.  -Matt

An arctic cold front is pushing southward across New England on our Wednesday, delivering a blast of arctic chill to especially Northern New England, but a chilly day is on tap for one and all.  Along and ahead of this cold frontal boundary - dropping south from Canada - snow showers have already begun to fall in scattered form, and they will continue to crop up throughout the day as cold air moving in aloft creates what we refer to as "instability" in the world of meteorology - that is, significantly colder temperatures aloft as compared to the surface.  This type of a setup allows billowing cumulus clouds to develop and it's these billowing clouds that grow large enough to drop snow showers for some communities across New England, and heavier snow squalls in the mountains and hilly terrain of both Northern and Western New England, from the Litchfield Hills and Berkshires, through the Green and White Mountains, and from the Lakes Region of New Hampshire to the Lakes and Mountains of Maine.  In these locales in particular, some squalls may be heavy enough to significantly reduce visibility briefly and coat roads with a slippery coating of fresh snow.  Elsewhere, snow showers will have less vigor, but a windy and chilly day will greet us as wind gusts to 30 mph cut a good 5-10 degrees off the actual temperature when we factor in the wind chill or "feels like" temperature.

With a bubble of high pressure - a fair weather center - breaking off of the cold arctic high that's been delivering record cold temperatures to the Northern Plains for several days now and moving to the East Coast, winds will stay active Wednesday night as New England will lay in the clockwise flow of air around this high pressure, bringing a steady northwest wind to the area.  The good news is that this fair weather center - though cold - is packed with dry air and that will lock in plenty of sunshine to battle chilly temperatures on Thursday.  Winds should abate somewhat as Thursday wears on, though high altitude cirrus clouds will be on the increase by late afternoon.  The old rule is that these cirrus clouds can often indicate precipitation within 18-36 hours, and that is likely to prove correct for the end of the week.

Because, while we enjoy a dry and chilly Thursday, two equally impressive storm centers will be moving into the Eastern United States.  The first of these storms is a strong energy center in the upper levels of the atmosphere that will move from the Central Plains into the Ohio Valley on Thursday.  Precipitation will be limited with this disturbance due to a lack of moisture - largely thanks to the expansive and dominating cold high pressure center mentioned above.  Farther south, a weaker storm will be taking shape in the Northern Gulf of Mexico - on the southern periphery of the large high pressure center - and this storm will tap loads of Gulf moisture as it develops over the warm waters and humid air.  Our problem will come as these two storms begin to interact Thursday night, resulting in a moist and energetic storm center developing off the Eastern Seaboard.

Overnight Thursday night, this coastal storm will charge northeast, and will have some similarities - and some big differences - from our previous storm (or lack thereof).  The similarities will focus on a storm track that moves south of New England, which means exact amounts will be dependent upon the exact track, and just how much moisture is pulled northward.  This storm will also be a similar merger of a northern stream, cold, energetic disturbance with a southern stream system containing lots of moisture, and there is always uncertainty on just how quickly and coherently two storms will merge.  Considering this inherent uncertainty, it would be irresponsible to put out exact amounts at this early juncture, but this storm most certainly has the potential for plowable snows to reach farther north than the last storm earlier this week.  And that brings us to the differences from the previous storm:  1)  The merger of these two systems will happen sooner than it did last time, which means the storm will be better developed when it passes south of us.  2)  This storm will tap more moisture from the Gulf of Mexico, since the southern stream half of it actually will originate in the Gulf, and this means the consequences of a hit would be much higher.  3)  Instead of a wind from the north, battling the advancement of moisture from the south, the clockwise flow around an area of departing high pressure will allow winds to turn from the south and help to carry moisture northward.  The bottom line of all this is that - while the details are far from being worked out - a logical and objective analysis of the event tells us there's much more to work with for storm development here, and plowable snow is likely to reach much farther north.  Finally, it looks as though the precipitation shield would not cut off as quickly on the north side this time around, a rain/snow line may come into play, and a coastal front would be possible (warm air on the east of it, cool air on the west, and a band of enhanced snow in the middle) if the storm sets up properly.  But again, we'll stay flexible until things become a bit more clear.

Behind the storm this weekend, somewhat milder air will actually move into our region from the southwest.  It's important to note that while this means temperatures are likely to rebound into the middle 30's, and that will feel good to the body after a cold stretch, those numbers are still below normal for this time of the year.  Saturday looks mostly sunny with a break between systems, but by Sunday a gentle feed of warmth and moisture aloft will mean clouds fill in across New England with most areas seeing more clouds than sun overall, and scattered showers of rain and snow by Sunday afternoon.

Overall, however, I still expect the cold and wintry pattern to prevail for the next couple of weeks, which keeps our chances for a White Christmas quite high in many parts of New England!

Have a happy hump day.

Matt

Matt's Technical Meteorological Discussion:  Updated Wednesday, December 7 at 1:40 PM

Arctic front moving thru NewEng today will continue touching off snow showers and heavier squalls thru the mountains of Northern and Western NewEng where orography assists in lifting along and ahead of front.  As mentioned in yesterday's discussion, lake effect snow band being picked up - at least in part - and carried east to bring blinding squalls to parts of the Berkshires and Litchfield Hills this afternoon.  Across the north, combo of dynamic lift and upslope flow will keep squalls and snow showers going even behind the arctic front.  This front loses its frontal characteristics as it moves through Southern NewEng but still provides enough cool push to either hold temps steady or back them down a bit - across the north temps should certainly fall this afternoon.

Overnight temps will drop into the single digits and teens - could have gone even lower but wind will stay active all night as high pressure builds in from the west and this will help to hold temps up a bit.  But combo of cold temps and active wind will bring windchills below zero and I've been stressing the cold overnight, the stress on the body and pets, and that homeless shelters are likely to be busy tonight.

Cold start Thursday will lend itself to a cold finish as bubble of high pressure moves over Mid-Atlantic and strengthens as it does so - from a 1039 mb high to 1042 mb!  This means we continue to hold the cold - no modification of airmass due to advection tomorrow surface through midlevel, though cirrus clouds will be on the increase from 400 mb and up late in the day.

As for our Friday system, I know I laid out a dissertation yesterday, so I'll spare you from a rehash and invite you to visit the archive at left, and just focus on changes/adaptations to thoughts today:

Both the 00Z and 12Z model guidance continues to exhibit the problem I discussed a few days ago of huge differences in model QPF, largely due to varying prognosticated mechanisms of phasing.  I'm going to simplify my thoughts here, only because it would probably take me all day to write them all out, but the bottom line on this is that a NAM/GFS blend actually falls quite close to a Canadian Ensemble mean with regard to precip amounts.  This blend also fits what I think may end up being the final scenario, which should prove the NAM too far north, and the GFS underdone on QPF.  With the influx of tropical moisture we'll be seeing, the NAM should perform superior to the GFS with regard to precip efficiency, though as of right now I think the NAM is overdone.  Everything from the 300 mb diffluence and jet streaks to the 500 mb vorticity to the antecedent low and mid level baroclinic zones indicate this storm center should stay south of NewEng, passing over or very near benchmark as it intensifies on its way northeast.  The NAM seems to be wrapping this storm too far into the cold air, and instead the arctic boundary that pushes through today, then settles Thursday, then returns Thursday night, should combine with the relatively warm ocean waters south of NewEng to create a low level baroclinic zone south of Long Island for the storm to link up with on its trek northward.  This will end up giving us a benchmark storm on Friday.  Wtih copious amounts of moisture feeding in and an antecedent arctic airmass that will be rapidly saturating in low level southerly flow, precip efficiency should actually be rather high with this event, which is why I think the GFS is likely underdone, especially as the precip shield expands northward beyond the MA Pike.  GFS Ensemble members have shifted slightly north in their MSLP tracks, and much farther north in their precip configuration, which fits these thoughts well.  Again, given the low level southerly flow that sets up, this is a different creature from the last few snow events on the South Coast and Cape Cod.  This time, enough warm air should certainly flood up from the south for a snow to rain in these locales though still too early for details on how much of each.  Additionally, coastal frontogenesis will occur with onshore flow and warmer air flooding over the waters, and this will create a ratio difference from coastline to interior.  Early enough in the season that I'd expect this coastal front to set up farther inland than just the immediate coastline, but may be more of a southwest to northeast orientation, which may allow for heaviest snow band to be oriented in this same fashion which...although too far north and perhaps overdone...the NAM is trying to hint toward this with its solution.  This will be a quick shot of precipitation that comes through, though it will be intense with the burst of warm advection.  Time frame still looks good on early Friday morning into Friday afternoon...then out of here by evening as once again a zipping and intensifying storm turns low level winds to a downsloping westerly direction.  All of this said, keep in mind that I did not give any exact amounts on the air this morning or at noon - with a great deal of model spread, it seemed irresponsible to put any exact amounts out there, only to risk changing them...and in some spots perhaps significantly...when more of a consensus is reached.  I do feel comfortable enough with all of the thoughts laid out yesterday and today, however, along with the consensus of American and Canadian operational and ensemble model members, to bring a line of plowable snow northward to the VT/MA state line, and to include most of Southern NH points southward.  I also felt comfortable enough about a probable mix for the South Coast/Cape Cod.

Saturday looks dry and milder, as mentioned yesterday, with a milder airmass advecting in from the southwest.  By Sunday, and approaching shortwave will combine with steady weak to moderate warm advection to produce plenty of clouds across NewEng (though perhaps not totally cloudy through the day) with scattered showers of rain and snow developing later.

Early next week yet another phasing system will move northward parallel to the East Coast, though right now it looks like extreme eastern areas would be the only ones watching out for a precip shield around the back of this system - particularly Eastern Maine.  And could we be entering a pattern of Friday storms?  Another threat for a cold coastal creature by next Friday as the mean longwave trough position sets up across the Ohio Valley with ample cold air and plenty of northern and southern stream waves for storm development.

Have a good Wednesday.

Matt

Snow Limited to Extreme Southern & Southeast New England...A Couple of Dry Days...Another Chance of Snow By Friday

Welcome to the weather blog - a regular Monday through Friday discussion of the weather!  You'll find a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow. If no technical discussion is available when you check in during the morning, check back later as it often comes after the Weather Summary - I try to indicate at the end of the general weather summary when/if a technical discussion is coming. My email is contact@mattnoyes.net.  While the discussions usually will only come on days I'm working, I'll occasionally issue special updates when the weather warrants.  This blog is for you, so I hope you enjoy it!  -Matt Noyes

For latest radar imagery, to check for watches and warnings, and for links to sites in the world of weather, feel free to click over to my website: www.mattnoyes.net

Matt's Weather Summary:  The storm center forecasted to move south of New England has made its move...but has maintained a sharp cutoff to its northern fringe of moisture while moving over the South Coastal waters.  The result has been no snow whatsoever in the interior, with higher amounts found in extreme Southern and Southeastern New England.  With the storm ready to wind down, I will spare you from a long-winded description of where the snowfall amounts will shake out, but the bottom line is everything laid out yesterday is cut by 2", except on Cape Cod, where yesterday's forecast of 4" will hold.  Elsewhere, we'll see nothing through most of interior New England, 1-2" on the South Coast of CT and Central RI.  The exception featuring a larger cut in snow totals was the area of 6" I'd forecasted for New Bedford to Plymouth, which only ends up with about 2"-3".  For those of you who were hoping to push snow around and weren't able to, I understand your frustrations and we'll see what we can do later this week and again the next few weeks.

As this storm continues to pull away from New England, it will strengthen steadily.  This will yank down a pool of cold air from Canada both at the surface and aloft, though the cold air will bleed gradually into New England today - allowing our temperatures to rebound into the 30's in many communities with breaks of sunshine emerging.  This incoming chill will bring temperatures either side of 20 degrees Tuesday night, and the result of the cold air aloft will be plenty of puffy "cumulus" clouds on Wednesday to blot out the sunshine from time to time, and scattered snow showers developing from these congested clouds.  Across the mountains of Northern and Western New England, where air is forced upward as it collides with the hilly terrain, heftier snow squalls are likely Wednesday afternoon.

A break in the action finally slides our way for Thursday, but later in the day yet another surge of warmer and more moist air will be organizing over the Southeastern U.S. and may take aim on New England with a swath of snow for Friday.  Understandably, I'm sure the meteorological community will be somewhat gunshy about this next event, but there are some facts that are important to lay out there:  1) This storm will be similar to the one we just had (or didn't have depending on your location) in that it will be the merger of a northern stream, cold, energetic system, with a southern stream system to supply moisture.  2)  The merger of these two systems will happen sooner than it did last time, which means the storm will be better developed when it passes south of us.  3)  This storm will tap more moisture from the Gulf of Mexico, since the southern stream half of it actually will originate in the Gulf, and this means the consequences of a hit would be much higher.  4)  Instead of a wind from the north, battling the advancement of moisture from the south, the clockwise flow around an area of departing high pressure will allow winds to turn from the south and help to carry moisture northward.  The bottom line of all this is that - while the details are far from being worked out - a logical and objective analysis of the event tells us there's much more to work with here, and the need to watch this storm carefully is even more than the last.  Finally, it looks as though the precipitation shield would not cut off as quickly on the north side this time around, a rain/snow line may come into play, and a coastal front would be possible (warm air on the east of it, cool air on the west, and a band of enhanced snow in the middle) if the storm sets up properly.  But again, these are just preliminary thoughts and we'll stay flexible until things become a bit more clear.

Overall, the cold and wintry pattern will roll on for the next couple of weeks, which keeps our chances for a White Christmas quite high in many parts of New England!

Enjoy your Tuesday.

Matt

Matt's Technical Meteorological Discussion:  Updated Tuesday, December 6 at 1:15 PM

Tight gradient precip event winding down after wreaking more havoc on forecasters than on the general public in most areas.  Reports range from around 4-5 inches CC/Islands to a couple inches South Shore to a coating Eastern MA coastline up thru North Shore and nothing interior where low level dry air evaporated snow on it's trip downward.  Caution will now, of course, be exercised with the upcoming event across the meteorological community, I'm sure, but let's be careful about this and understand that this is another event we'll have to get right back up on the saddle for, as it will be an equally challenging circumstance but with much higher consequences as there is much more moisture involved here.

But let's not get too far ahead of ourselves.  First is breaking clouds from west to east this morning into early afternoon as drier air moves in from the west.  Cold advection is underway in the wake of our departing and now rapidly strengthening storm center, though sunshine and developing downsloping flow of dry air will help to hold temps up in a lot of Central and Southern NewEng.  That effect on temperature wanes overnight as most areas fall to around 20 with lots of areas down into the teens.

Arctic front pressing south through Quebec and Ontario this afternoon will move into Northern Mountains on Wednesday early AM where orographic lift will enhance upward vertical motion for snow showers and heavier squalls that may cause treacherous driving conditions on some roads.  Behind this front, substantially colder air moves southward and highs will only be in the teens across the far North Wednesday afternoon.  Elsewhere in New England, I'm expecting the passing arctic front to interact with ongoing lake effect snow bands off of Lake Ontario to give a revitalizing shot of moisture for enhanced Wednesday afternoon snow squalls from the Berkshires into NW CT.  The rest of NewEng will be in a downsloping regime and this will limit lift, though Lakes Region should see some decent squalls with arctic frontal passage and then scattered snow showers from building cumulus later in the day elsewhere with sunshine between them.

Thursday looks cold but quiet for all of New England with a bubble of surface high pressure detached from tremendous arctic high over nation's midsection.  This 1040 mb surface high in the center of the country suppresses the effects of a strong vorticity maximum dropping into the Central Plains so that low pressure development takes place in an area of falling heights off the Texas coastline Wednesday night into Thursday.  This is the low that all will be watching carefully in NewEng for the end of the week, as it will parallel the Gulf Coast to Tallahassee, then trek inland over the Southeastern US coast.  As cyclonic vorticity advection and mid level warm advection shifts to the coastline Thursday night, so too will the surface low pressure center jump, and a swath of warmth and moisture will begin its surge northward.

Obviously model guidance is everywhere for this Friday.  The bottom line is this:  A more potent storm, with much more Gulf moisture putting out inches of rain in the Tennessee River Valley, will interact with a more potent vorticity maximum coming through the midwest in the northern stream.  I know meteorologists are gunshy after this last event, but these are the facts of the next creature and we should acknowledge that.  And, as mentioned yesterday, once again we're finding huge spreads in model guidance for this event.  But again, there are some basics that are across the board which includes:  1) A much less defined northern edge to precipitation, such that light precipitation should be able to creep northward to somewhere in the vicinity of the Canadian border, 2) Higher precipitation amounts reach farther north, 3) A mostly snow event for New England, 4) The possibility of a mix at the South Coast.  These all make sense synoptically, as well, given the high pressure center shifting east of New England during the period, allowing winds to go southerly in the low levels, which is something we didn't have with this last event.  It also makes sense given the additional input of Gulf moisture and the slightly farther north origin of the northern stream shortwave.  Timing has been relatively consistent on the guidance for an event that begins early Friday and lasts through much of the day.  A coastal front would be likley with this event.

The air behind this storm will be in here for the weekend, but shouldn't be a load of cold - instead, modified air comes in from the southwest for the start of the weekend.

Lots to keep our eyes on - looking forward to more tomorrow.

Matt

Tricky Plowable Snow Appears On the Way For Some...

Welcome to the weather blog - a regular Monday through Friday discussion of the weather!  You'll find a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow. If no technical discussion is available when you check in during the morning, check back later as it often comes after the Weather Summary - I try to indicate at the end of the general weather summary when/if a technical discussion is coming. My email is contact@mattnoyes.net.  While the discussions usually will only come on days I'm working, I'll occasionally issue special updates when the weather warrants.  This blog is for you, so I hope you enjoy it!  -Matt Noyes

For latest radar imagery, to check for watches and warnings, and for links to sites in the world of weather, feel free to click over to my website: www.mattnoyes.net 

Matt's Weather Summary: 

4 PM Monday Update:  Everything looks on-track thus far.  At least, that is to say I don't see any reason to change the forecast, so I will hold the line.  See you on TV Tuesday morning...previous discussion below.

Snow is on the way Monday night into Tuesday for Southern New England.  Let's start from the beginning:  A small area of cold high pressure is located over Delaware this Monday morning and New England is squarely in the heart of this cold air with morning low temperatures starting out in the teens and 20's through both Northern and Southern New England.  A cold front draped south of New England across the Mid-Atlantic and Southeastern U.S. is focusing a flow of moisture out of the Gulf of Mexico and this has been producing Monday morning rain across those regions.  Along this cold front, waves of low pressure are rippling northeast - traveling along the tight temperature difference between temperatures near 60 in the Carolinas and single digits by Chicago!  This pathway runs south of New England and will serve as the route our upcoming storm will follow.

The northern fringe of this moisture feed has been moving over New England this Monday, with high altitude cirrus clouds bringing overcast skies to some of Southern New England.  After such a cold start, limited sunshine will mean limited heating - and therefore most spots will fall either side of the freezing mark Monday afternoon.  Our bubble of cool high pressure nearby is also thankfully a bubble of dry air, so our Monday will stay dry, with black ice on secondary roadways, sidewalks and entrance/exit ramps to interstates our biggest concern through the morning, and a fairly carefree evening ride home.  Monday night, moisture will continue to increase from the south, and snow should reach the South Coast of New England prior to midnight.  The remainder of Southern New England will find snow moving in after midnight.

Tuesday morning we're likely to find a snowy start for most of Southern New England as the most impressive low pressure center of the bunch passes south of New England along the frontal boundary mentioned above.  This low pressure center is likely to pull enough warm and moist air northward in the upper levels of the atmosphere to create snow in many areas.  A northerly and northeast wind will ensure that cold air stays in place for most areas, and this will mean the snow should fall either side of a ratio of 15 inches of snow to 1 inch of water.  This should bring amounts of 2" from extreme Southeast NH, to the Merrimack Valley of Northeastern MA, to Worcester and southwest through Hartford, Waterbury and Danbury.  Farther north and west, only a dusting to an inch of snow is expected by Tuesday afternoon, until you get north of a line from Rutland, VT to Brunswick, ME, where very little accumulation is expected.  Farther southeast, I'd expect about 3" around the city of Boston, perhaps 4" on Cape Ann, and 4" from the South Shore of MA south of Boston to Marshfield/Duxbury running southwest through the Brockton area and into Southeast CT.  My highest forecasted amounts are 6" of snow by Tuesday afternoon from Duxbury, MA, south to East-Falmouth and through New Bedford and Central/Southern Rhode Island.  In this zone, it's possible a few communities record 7 or 8 inches.  On Cape Cod, however, the situation becomes trickier.  While there is plenty of cold air in place and a northeast to north wind is forecasted - normally great conditions for snow even on the Outer Cape and Islands - ocean water temperatures are running in the middle 40's.  A wind off the ocean waters - even from the north - should warm the temperatures near ground-level enough that as snow falls, it will compact and become heavy and wet, limiting accumulations to either side of 4" east of East Falmouth.  With all of these amounts, it's important to understand the uncertainty that still lingers with this storm regarding: 1) How far north precipitation actually makes it, and 2) the amount of precipitation that falls from the sky.  I'll be reviewing the late morning data and post an update if it looks like things are changing.

With the storm center strengthening as it moves south of New England, a tail of snow is likely to linger over eastern parts of Southern New England into the afternoon on Tuesday - though the heaviest snow will fall during the morning.  By evening, even the light snow will end, and winds come around to a drying westerly flow to break up the clouds during the overnight Tuesday night.

As this storm pulls away from New England, it will strengthen steadily.  This will yank down a pool of cold air from Canada both at the surface and aloft.  The result of the cold air aloft will be plenty of puffy "cumulus" clouds on Wednesday to blot out the sunshine from time to time, and scattered snow showers developing from these congested clouds.  Across the mountains of Northern and Western New England, where air is forced upward as it collides with the hilly terrain, heftier snow squalls are likely Wednesday afternoon.

A break in the action finally slides our way for Thursday, but later in the day yet another surge of warmer and more moist air will be organizing over the Southeastern U.S. and may take aim on New England with a swath of snow for Friday.  Overall, the cold and wintry pattern will roll on for the next couple of weeks.

Matt

Matt's Technical Meteorological Discussion:  Updated Monday, December 5 at 11:45 AM

The trend thus far in this winter pattern has been disturbing with the guidance - most events feature great disagreement among numerical weather prediction until the event is at hand, and no one model has emerged a clear winner - or a clear loser for that matter.  The pattern continues, and synoptically it does make sense that the guidance would have trouble handing this setup of deep tropical moisture tap interacting with intense northern stream energy for multiple phasing events.  What's more is that this phasing occurs as the systems move near or through NewEng, and that means phasing details have become critical to each forecast, and each model handles the phasing dynamics differently, especially when convective parameterization comes into play with the warm waters off the Mid-Atlantic and Southeastern US touching off organized convection.

But the task at hand is once again to decipher the hidden meteorological code in all of this mess, and for that begin synoptically:

1022 mb high centered over NJ is a breakaway bubble high from the main surface ridge present over the nation's midsection.  The cold associated with this bubble high is serious - produced widespread lows in the teens and 20's this morning - and will be sufficient for widespread snow...mostly.  Double barrel 1014 lows rippling along cold front over SE US with 16Z analysis placing one low center over SC and another over FL panhandle and both moving NE.  It is the latter of these that will be the main player in NewEng weather as it strengthens along the low level baroclinic zone while encountering weak upper level diffluence ahead of moderate cyclonic vorticity advection associated with incoming northern stream shortwave moving east from the midwest.  The net result of this merger is for a Gulf of Mexico juiced up low to develop into a deep gale center...but likely not until pass east of our longitude.  The questions and concerns associated with this event come with uncertainty to the intensity and northward expansion of the precipitation shield on the north side of the storm, associated with midlevel warm and moist advection.  All low level advection, including at 850 mb, is cold and dry, but at 700 mb postive Theta-E advection will commence this evening, and continue thru Tue AM.  It will be these mid and upper level dynamic laid out above that will govern development of this as a storm to affect New England.

So let's lay out the obvious from this analysis right off the bat:  It's going to be hard to get a blockbuster storm out of this given its speed, delay in deepening and lack of low level dynamics to help generate a conditionally unstable low level environment.  That being said, the air being advected northward around the developing midlevel center is tropical in nature, the thunderstorms firing off the Carolina coastline are indicative of the depth of this moisture, and we certainly can crank out some decent amounts from a setup like this, especially given that the South Coast of NewEng is going to be on the cool side of this conveyer belt.  But also at work here is the relatively sharp cutoff of midlevel warm and moist advection forecasted by the guidance - as the southerly flow ahead of this developing midlevel center is thwarted by prevailing westerly flow from 700 mb up.  This may create a level of midlevel directional convergence which can enhance upward vertical motion, but also should allow for a relatively sharp cutoff of significant snow, if not of the snow shield entirely, which may extend farther north thanks to varying "degrees" of warm advection with altitude (pun intended!).

Even now, down to the wire, QPF amounts differ rather significantly among most of the guidance, though the trend is clear:  A tight gradient in significant QPF amounts decreasing from SE to NW.  As for the timing of this event, I'm bringing snow onto the South Coast of NewEng about 10 PM to midnight, then expanding farther north after midnight.  The synoptics described above dictate snow will fall heaviest during the early to mid morning on Tuesday, when positive Theta-E advection is maximized and vorticity advection enhances upper level diffluence.  Thereafter, a north-northeast wind for a time will actually bring low level dynamics into play as the storm departs - after being a relative non-factor during the meat of the event, this northeast drain of shallow cold advection should provide a differential advection setup for a tail of light snow to continue into the afternoon in Eastern NewEng.  By evening, the low level winds shift to a more westerly direction, favoring downsloping and drying.

My accumulation forecast has been laid out both on-air and in my weather summary above.  Some of you will look at my thoughts for Cape Cod east of East Falmouth in that summary and think I'm out to lunch.  And you may be right - there's certainly a part of me that asks what in the world I'm thinking.  That being said, I think it's important to think about this from all angles.  Yes, lift will be intense.  Yes, there will be dynamic cooling taking place.  Yes, a north to northeast wind at the surface is nearly perfect for heavy Cape Cod snows.  Yes, cold air is in place already.  So why shouldn't this indicate a blockbuster storm for the areas progged to get the most QPF?  It's all about ratios.  My thinking is this:  For most of the area, maximum lift occurs between 500 and 600 mb, and the temperature is cold enough that it's primarily needles and columns forming with regard to ice crystals.  850 mb temperatures are not warm enough to favor significant aggregation, and though snow will be fluffy, ratios will not be as high as they could be.  Then as one moves farther south and east there will be a "sweet spot" for ratios where the maximum vertical ascent lines up perfectly with the dendritic crystal growth layer, and that appears to me to be roughly from New Bedford points northeast, and this persists until East Falmouth.  Farther east than that, something was evident to me right from the start of the day - minimum temperatures were much higher, dewpoints were higher...in other words, the air is ocean modified.  Then I remembered the snow from this weekend, which I'd thought on Friday was going to have to mix with rain on the Cape and the Islands.  To be honest, I didn't expect MVY to report 1.5" before changing to rain and washing it all down the drain, and that certainly had me worried about this event.  If they did it then, what's to stop them from doing it this time, especially with a north-northeast wind that should, in snowstorm theory, keep these areas all snow?  The problem is the 46 degree ocean temperatures.  Yes, the ocean was 46 degrees for Sunday's snow on the Outer Cape and Islands, but the snow came when - and here's what I think is critical - when the wind was calm.  It snowed with a calm wind on the islands and the outer cape, but as soon as that wind went northeast and kicked up, the temperature rose, the dewpoint rose, the snow melted off the ground and eventually the snow turned to rain.  And that was with an antecedent dewpoint of 12!  This time it's in the 20's to start.  So now I look at a mean QPF that may be as much as .55-.60" in these locales, and I can buy the argument that vertical motion and cold air through the column will combine to keep the precip type all snow in these locations, but I have to believe that a shallow layer of ocean modified warmth will wreak havoc with accumulations here, allowing snow to compact significantly, and I can't buy more than an 8:1 ratio, which gives me less snow on the Outer Cape and Islands than in the New Bedford to Plymouth corridor.

As snow winds down late Tuesday afternoon (after low level light snow ends) it's due largely to downsloping winds taking over.  Wednesday 500 mb temps are around -35 C...Yikes!  Cold stuff and cold enough for instability snow showers and heavier squalls in the mountains.  A break on Thursday though another fairly substatial shot of warm and moist advection will be trucking northeast through the Tennessee River Valley later Thursday and will provide another close scoot of a strengthening low pressure center passing south of NewEng on Friday.

Thereafter, chances for a White Christmas seem to go through the roof!  I say this largely because the mean trof position sets up over the Ohio River Valley and this is a great location for large coastal storms to develop that do indeed affect New England.  So, the transition in the longwave pattern appears ready to shift to one that left me saying a couple of weeks ago that we were heading into a period of numerous coastal waves that would be close shaves regarding their effects on New England, to a pattern now through Christmas where I can say chances are very good we'll see some sizeable storms of snow, even in Southern New England.

Enjoy.

Matt

Where's the Northern Mountain Snow? Southern New England Remains on Track...Cold Air Spilling In...Southern Sunday Snow Still Possible

Welcome to the weather blog - a regular Monday through Friday discussion of the weather!  You'll find a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow. If no technical discussion is available when you check in during the morning, check back later as it often comes after the Weather Summary - I try to indicate at the end of the general weather summary when/if a technical discussion is coming. My email is contact@mattnoyes.net.  While the discussions usually will only come on days I'm working, I'll occasionally issue special updates when the weather warrants.  This blog is for you, so I hope you enjoy it!  -Matt Noyes

For latest radar imagery, to check for watches and warnings, and for links to sites in the world of weather, feel free to click over to my website: www.mattnoyes.net

Matt's Weather Summary:  First thing's first this Friday morning - the forecast for Northern Vermont and New Hampshire has failed to materialize.  We still WILL see a few inches of snow in the mountains of Vermont and New Hampshrire, and in fact, we'll still see over half a foot at places like Jay Peak in North Central Vermont by overnight Friday night, but actual amounts compared to yesterday's forecasts valid through Friday evening will fall some 2-4"shy of actual amounts.  In valleys of the North...and through all of Southern New England...the forecast remains on-track.

Patches of flurries, snow showers and light rain showers moving across New England Friday morning are an indication of colder air spilling into the six-state region, and Friday will be a blustery day with plenty of clouds, limited sunshine, and periodic light showers of rain and snow in many locales.  In southern New England, a west-southwest wind will be quite active, and while this wind sloping down off the hilly terrain usually can warm us up handily, the air moving in is simply too cool to allow for this effect - instead we'll find lots of clouds, breaks of sunshine, scattered flurries and sprinkles, and temperatures nearly holding steady through the day in the upper 30's and a few areas cracking into the lower 40's briefly.  For those of us in Northern New England, the Friday morning weather analysis shows two areas of low pressure still in the process of consolidating - one pulling through Maine, and the other scooting across the Canadian border of New York and Vermont.  These two storm centers are merging into one as they pull into Southern Canada, but the original expectation was for them to combine over the Gulf of Maine.  This delayed merger has meant that instead of one congruous area of precipitation, we've instead seen rains move through Maine, and now the snows will follow for Northern New England in light fashion throughout Friday and into Friday night.  This still should drop 3-4" up the spine of the Green Mountains, 1" in the Berkshires, around 6" in the high terrain of extreme northern VT, and a couple of inches in the White Mountains.  But without the additional input of moisture from the rain making storm in Maine, that's about all we can squeeze out in ski country this time around. 

It's these merging storm centers in Canada that will keep a strong wind blowing...eventually shifting to the west-northwest by Saturday...and ushering in a significant chill to New England for the end of the workweek and the upcoming weekend.  I wouldn't be surprised to find this arctic shot of air holding temperatures only in the 20's to around 30 for just about everyone on Saturday!  The good news for Saturday is that this cold air is also relatively dry air, which means we should be able to bring out the sunshine - and we'll need it!  With temperatures struggling to reach 30 degrees and an active wind gusting over 30 mph at times, the wind chill, or feels like, tempertures will be dipping into the lower 20's!

While we stay quiet on Saturday, a new storm center will be taking shape across the Tennessee River Valley.  This storm will tap moisture out of the Gulf of Mexico, and be comprised of an upper level disturbance of moderate strength dipping through the Midwestern United States, caught in the jet stream winds aloft.  As this storm center moves northeast later Saturday, a wintry mix of precipitation will move through the Ohio Valley.  By Sunday, I'm expecting this storm center to scoot south of New England, but that's not the end of the story.  Though the storm will be weakening, it still will likely be strong enough to pull just enough warmth and moisture northward into our cold air dome to create a sufficient clash of airmasses for snow to develop.  This discussion being written Friday morning, remember that this is an early juncture, but it looks like at least light snow will reach into extreme Southern Vermont and New Hampshire points southward, with an inch to two inches possible from the Massachusetts Turnpike points southward.  On Cape Cod, winds will blow from the northeast, but the ocean waters are still warm enough that we're likely to see a mix with rain.  While this discussion won't be updated again until Monday, I'll try to update my forecast (at left) from time to time over the weekend, and of course Joe Joyce will be on NECN with the updates over the weekend.

Our weather pattern remains favorable for colder than normal temperatures and a higher propensity for coastal storm development through next week and likely through the first half of December.  What this means for us is that a series of storms will develop along the Eastern Seaboard the next couple of weeks, and the chances are higher than normal for a widespread accumulating snowstorm or two.  That being said, it's very important to remember exact track of the storms is always critical, and while the possibility is there that we get socked a time or two, there's also the chance that they miss - from this far out in a volitile atmospheric setup like the one we have, it's really more about pattern recognition than exact details, for fear of misleading anyone with details that are sure to change with due time.

At this point, there's one storm threat early next week - likely Monday night into Tuesday - which will be another storm that may or may not ride far enough north to put New England into widespread snow and rain...then another threat toward the end of the week.  My next discussion comes out Monday morning, and certainly you can expect many more details on next week's weather by then.

Matt

Matt's Technical Meteorological Discussion:  Updated Friday, December 2 at 11:50 AM

Failed storm merger means failed forecast in parts of Northern NewEng, but it's not over yet.  Yesterday's forecast ranged from 3-5" in the Greens by Friday eve to 10" Jay Peak to 3-5" White Mountains and an inch in the valleys.  I've taken out all valley accums excepting a dusting or coating which has already fallen and will continue to affect some areas.  Today's forecast still ranges from 1" Berks to 3-4" Greens (though much narrower band focused only on high terrain) to 6"+ Jay Peak area to 3-4" higher terrain of Whites with a sharper cutoff to nothing but a dusting in Central Grafton and Central Carroll Counties, and same in the Southern half of Vermont's Northeast Kingdom.  Maine mountains still look good with 1-3".

Obviously energy running up low level front didn't interact with incoming vorticity maximum soon enough for many (any) fireworks overnight outside of Central and Eastern Maine, where 1-2" of rain fell.  Today I expect the upper low moving across Northern NewEng to bring enough low and mid level instability with its associated cold pool aloft for increasing intensity of orographically induced snows along the moutainous upslope favored areas.  As mentioned yesterday, downslope flow for the remainder of NewEng is likely to serve more as a drying agent for lingering low level RH rather than much warming effect on temps as cold advection is already underway (many areas dropped in temp even after sunrise).  925 mb winds to 30-35 kts aloft mix down periodically for gusts to 30 mph.

Winds stay remarkably active tonight as storm deepens in Eastern Canada and pressure gradient tightens.  This also hastens cold advection and surface trough swinging through NewEng this evening reorients winds to the west-northwest and unloads a chunk of modified but significant cold that's been sitting over the Upper Great Lakes.  Saturday still looks quite cold with most areas struggling to get above 30, and with winds gusting to 30 mph through Saturday as well, this brings wind chills into the low 20's for many areas.  Shortwave parade still expected to bring snow showers and heavier squalls to mountains Saturday and with bone dry air at 700 mb elsewhere, sunshine will be out.  Cirrus clouds begin riding into Southern NewEng as soon as Saturday afternoon well in advance of next system.

700 mb RH progs continue to ride farther and farther north with the area of 70%+ RH, and precip is riding farther north accordingly with Sunday system.  For now, have brought northern extent of precip to extreme Southern NH and Southern VT with accumulating snow of 1-2" from Massachusetts Turnpike points southward but north end of that is tenuous and I feel more secure from MA/CT line to South Shore points south.  Speaking of South Shore, air will be plenty cold for snow but ocean is still in the upper 40's and we have to put mix in for South Shore MA and Cape Cod/Islands as well as South Coast RI and SE coast CT.  Bottom line here is that today's frontal boundary is thrust southward overnight and then holds steady south of NewEng on Saturday.  By the time it returns ahead of next wave, it won't make it farther than off the south coast of Long Island and this should serve as the path for the surface low.  In a synoptic setup like this with a strengthening storm, the potential exists for a 4-6 inch snowfall with higher amounts.  But given that this wave is weakening on its path south, it should be more an example of a storm that's exhausting what it has for warm advection - enhanced by low level Atlantic inflow.

Most of Monday should be dry as a bubble high pressure center builds overhead.  This bubble high is detaching from the well of cold air over the Northern Tier of the US and should come with well-established cold.  Then comes the shortwave that everyone is talking about in the weather world.  There is terrible agreement among the guidance on how to handle this shortwave and when/where to strengthen it.  GFS obviously is going off on this storm and has finally placed it correctly timewise - Monday night into Tuesday.  While the other operational guidance isn't keying in on this as emphatically, the synoptics say it's going to have to be Monday night into Tuesday or the opportunity will have passed, so this is the timeframe any chance of snow/rain should go in.  Shortwave ridging helps to breed anomalously high heights from the Mid-Atlantic coast on Monday to the Western Atlantic on Tuesday, and it would be this shortwave ridging that would allow any storm development to take place.  GFS Ensemble mean MSLP fields show a coastal wave passing rather flat south of NewEng.  Canadian Ensemble members show a rather large spread in this same field.  850 mb temp anomalies indicate a rather flat west to east baroclinic zone, but very tight gradient between anomalously cold and anomalously warm, and this is terrific breeding ground for amplification of the shortwave as it moves east and over the relatively mild Atlantic waters.  Finally, GFS Ensemble means indicate a plummet from near normal to below normal heights over the Northeast from  Monday to Tuesday behind this shortwave, and this leaves room for the falling heights in the Northeast to be the result of an amplified short.  Bottom line is this:  It's still too early and too uncertain for any forecaster to feel confident on this as far as I can tell.  That being said, we have favorable low level baroclinicity and dynamics for a storm to quickly ramp-up, and the key will likely be the degree of shortwave ridging over the Western Atlantic ahead of the wave.  The breakaway high over us at the surface will mean cold air will be well enough entrenched for a mainly snow event, as it will force the very same frontal boundary from Sunday's event south of us once again, though the ocean will modify coastal locales.

Have a great weekend!

Matt