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November 2006

COOLER WEATHER GRADUALLY SETS IN...FRONT TO BE STUBBORN CLEARING NEW ENGLAND THRU THURSDAY

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

General Weather Summary:

This summary is a bit late today...

Weatherwise, New England is sandwiched between two weather systems today - a Bermuda high to our southeast with a clockwise flow of air around it, and a low pressure center in the Great Lakes with counter-clockwise flow...ushering a strengthening southwest flow between them and pushing mild air into New England.

The axis of a surface high pressure system - a fair weather cell - moving south of New England crested over New England Monday night and was responsible for our cold Tuesday morning start, with freezing fog reported in Lebanon, NH.  This chillly start has been offset by the southwest winds, ushering in warmer air that's been producing daily high temperatures in the 60s, 70s and 80s across the nation's midsection.  This air will bring similar results to New England, placing us on the cusp of the deeper warmth and bringing many spots into the 60s Tuesday afternoon, even with filtered sunshine through increasing high-altitude clouds.  These increasing clouds are traveling ahead of a disturbance aloft, riding along the Canadian border and carrying an associated surface storm and cold front with it.  While a few showers have been trying hard to jump Lake Champlain out of New York - and will succeed later in the afternoon, bringing light rain showers to Northern Vermont and New Hampshire by day's end.  Elsewhere, clouds will lower and thicken gradually Tuesday night with a few showers late at night, possibly lingering into early Wednesday morning with the passage of the cold front.  Behind the front, drier air will move in and some sunshine will return during the day Wednesday, though cooler air will filter in as another cool stretch of weather settles in for several days.  The result will be falling daily temperatures all the way to the end of the week.

The trick here is that this cold front is likely to slow and then stall late Wednesday across Southeastern and far Southern New England.  This will not only result in healthy development of puffy cumulus clouds Wednesday afternoon, but will also help to focus moisture ahead of another disturbance that will be racing northeast out of Southern Pennsylvania late Wednesday, allowing rain showers to develop over New England late Wednesday night into Thursday.  With such a slow moving front, chances are good it will be very hard to kick these showers and clouds out entirely until passage of the next disturbance, slated for Thursday night.

By Friday, a new disturbance aloft will bring a returning chance of showers to New England by evening, especially across Northwestern New England, but by this point colder and drier air will be spilling in, which means a band of lake-effect snow showers off Lake Ontario is likely, carrying into the Green Mountains, with a much slighter risk of precipitation elsewhere.

As for the longer range pattern, a shot of very chilly air will move in behind Friday night's showers, delivering a hearty shot of cold air through next weekend.  By early next week, the jet stream pattern will undergo a major shift - in this case called a "retrogression" where the cool dip in the jet stream winds aloft moves westward.  The result will be a warmer than normal pattern - at least on average - that may last through the first half of November.  Rest for the weary?  That very well may be the case.

Have a great Tuesday!

Technical Discussion:  None today.

Matt

Matt's Technical Meteorological Discussion:  Updated Monday, October 30 at 2:30 PM

Relatively quiet in the short term as winds subside this eve with decreasing PG - but only briefly as strong SW gradient has established over OH Valley.  Air advecting thru the boundary layer toward NewEng has history of 60s and 70s and will be in place Tue, tho with shifting winds slackening under sfc ridge axis overnight, expect valleys to decouple with frost while most areas land in the 20s and 30s, esp given that Tds currently running in low to mid 20s.  Cold start Tue to be moderated by aforementioned SW flow and help from insolation.  Full insolation with 925 mb temps would support temps over 70 in Srn NewEng, but decent moisture connection already evident on satellite imagery today over the Central and South-Central US is well modeled and progged to move overhead on Tue, limiting insolation by at least filtering sun.  Mixing will be a bit limited thanks to this cloud cover, and coupled with cold start, temps shud land in mid 60s most areas of Central/Srn NewEng...tho CT river valley may be able to hit 70.  This will leave a mild eve for trick-or-treating as mild flow continues in advance of shortwave moving east across the Nrn Plains as of this writing, and that will be moving thru Srn Canada on Tue.

Xpct showers Tue ngt - after 00Z - that will amount to between .01 and .15" of QPF (perhaps a bit higher in upslope favored areas) as low level moisture feed will have trouble establishing into such a dry antecedent airmass.  Air will be warm enough for rain all areas with plenty of warmth aloft.  Colder installments thru the end of the week with next shortwave slated for later Fri with chc showers from NW to SE later in the day, ushering in next fortified shot of chill in a steadily declining temp regime into the weekend.

The longwave pattern will actually favor recoiling heights northward quickly behind the shortwave on Fri as Srn Canada upper low is absorbed into deepening very strong polar vortex near the pole.  But left behind in fast westerly flow will be new energy ejecting from the Aleutian low, and this will help to maintain cool flow sfc and aloft into New Eng until these cold shortwaves pass later in the weekend.  Thereafter, strong Pacific energy will be trying to close off briefly over the Midwest, and while it may not live long, it will lower heights enough for energy continuing to shoot east from the strengthening Aleutian low - feeding off southward seeping energy from the polar vortex - into this new developing trough.  This feed of air from polar vortex to Aleutian low to Intermountain region will assist in longwave retrogression, with trough settling to our west, and putting NewEng in developing deep SW flow.  This sets up a pattern that will favor both warmth, and rainfall into NewEng for the first half of November, with the warmth coming on by next Mon/Tue, and the moisture not too far behind - likely a decent rain event MidAtl to Northeast mid to late next week as energy continues to eject from base of new trof, carrying Pacific subtropical moisture and tapping Gulf moisture.  Though this results in building northeast warmth thru the first two weeks of November, winter lovers should not lose hope here, as the retrogression will cease and the weather pattern become a bit more progressive by the latter half of the month, largely thanks to a super-ridge to develop across the Nrn Pacific, eventually dislodging both the energy and cold out of Alaska while NewEng warmth should serve as fuel for pumping heights to our east and building a rather impressive block over Greenland the latter half of the month.

So, in the short term we see cold persisting and in fact providing one of our cooler shots thus far for the upcoming weekend - likely to be accompanied by at least some upslope snows - before we see our pattern shift to warmth, then wet and warm...all perhaps en route to a different second half of November.

In the meantime, ski resorts should be able to take advantage of good snowmaking weather most nights except Tue Ngt of this week, through Mon Ngt of next week.  Make the most of it if you want to get the early start on the season, as you'll need a base that can survive only occasional snowmaking capabilities Nov 7 thru 14.

Matt


AFTER A WEEKEND OF DAMAGING WIND, MUCH QUIETER WEATHER GRADUALLY TAKES HOLD

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

General Weather Summary:

After a weekend of damaging winds, gusty winds will continue on Monday though are unlikely to reach damaging criteria.  These winds have been the result of the strengthening storm that soaked New England on Saturday, whitened parts of the North Country Saturday night and Sunday, and reached peak strength in Eastern Canada.  With the storm pulling farther northeast away from New England while weakening, winds will gradually subside, clouds will gradually break, and the weather will gradually improve.

Storm Photos:

From Hull, MA, where Michael Page reported significant street flooding and wind damage:Octstorm7

From Hyannisport, MA, where Peter Spang reports this boat broke free from its mooring: Octstorm6

From Sugarloaf/USA, ME, where Bill Swain reports the flakes were flying: Octstorm5

From Allston, MA, where Andrew Abramowitz grabbed photos of a car and driver that were under a falling tree.  Amazingly, Andrew reports the woman in the first car was uninjured: Octstorm4

And finally, three pictures taken by Dick Sharron in and around Glen, NH, at varying altitudes.  High water at Rocky Branch River in Glen, two inches of snow at the top of Iron Mtn. Road at 1900' in elevation, and golfers enjoying the day at the bottom of the very same road, elevation 800': Octstorm1 Octstorm2 Octstorm3

The improvement begins Monday, with the shield of low-altitude clouds quickly retreating northeast and dry air replacing them to provide for widespread sunshine.  From Portland, ME, points north and east, enough cold air remains aloft for numerous clouds to continue building in the difference between relatively warm land and chilly air upstairs, resulting in mostly cloudy conditions for most Central and Eastern Maine Monday afternoon.  Where sunshine emerges, the active wind gusts to 40 mph will help to ensure the atmosphere is well-mixed through the lower few thousand feet, and this will allow temperatures to rebound to near 60 in some Southern New England locales, especially in the Lower Connecticut River Valley.

The axis of a surface high pressure system - a fair weather cell - moving south of New England will crest over the six-state region Monday night, bringing mainly clear skies, light winds, and resultantly cool temperatures with frost in many valleys.  This chillly start will be offset by shifting winds on Tuesday, blowing from the southwest and ushering in warmer air that's been producing daily high temperatures in the 60s, 70s and 80s across the nation's midsection.  This air will bring similar results to New England, placing us on the cusp of the deeper warmth and bringing many spots into the 60s Tuesday afternoon, even with filtered sunshine through increasing high-altitude clouds.  These increasing clouds will come ahead of a disturbance aloft, riding along the Canadian border and carrying an associated surface storm and cold front with it.  Clouds will lower and thicken gradually Tuesday night with a few showers late at night, possibly lingering into early Wednesday morning with the passage of the cold front.  Behind the front, drier air will move in and sunshine will return during the day Wednesday, though cooler air will filter in as another cool stretch of weather settles in for several days.  The result will be falling daily temperatures - but continued sunshine mixed with clouds from time to time - all the way to the end of the week.

By Friday, a new disturbance aloft will bring a returning chance of showers to New England by evening, especially across Northwestern New England.

As for the longer range pattern, a shot of very chilly air will move in behind Friday night's showers, delivering a hearty shot of cold air through next weekend.  By early next week, the jet stream pattern will undergo a major shift - in this case called a "retrogression" where the cool dip in the jet stream winds aloft moves westward.  The result will be a warmer than normal pattern - at least on average - that may last through the first half of November.  Rest for the weary?  That very well may be the case.

Enjoy your Monday!

Matt

Matt's Technical Meteorological Discussion:  Updated Monday, October 30 at 2:30 PM

Relatively quiet in the short term as winds subside this eve with decreasing PG - but only briefly as strong SW gradient has established over OH Valley.  Air advecting thru the boundary layer toward NewEng has history of 60s and 70s and will be in place Tue, tho with shifting winds slackening under sfc ridge axis overnight, expect valleys to decouple with frost while most areas land in the 20s and 30s, esp given that Tds currently running in low to mid 20s.  Cold start Tue to be moderated by aforementioned SW flow and help from insolation.  Full insolation with 925 mb temps would support temps over 70 in Srn NewEng, but decent moisture connection already evident on satellite imagery today over the Central and South-Central US is well modeled and progged to move overhead on Tue, limiting insolation by at least filtering sun.  Mixing will be a bit limited thanks to this cloud cover, and coupled with cold start, temps shud land in mid 60s most areas of Central/Srn NewEng...tho CT river valley may be able to hit 70.  This will leave a mild eve for trick-or-treating as mild flow continues in advance of shortwave moving east across the Nrn Plains as of this writing, and that will be moving thru Srn Canada on Tue.

Xpct showers Tue ngt - after 00Z - that will amount to between .01 and .15" of QPF (perhaps a bit higher in upslope favored areas) as low level moisture feed will have trouble establishing into such a dry antecedent airmass.  Air will be warm enough for rain all areas with plenty of warmth aloft.  Colder installments thru the end of the week with next shortwave slated for later Fri with chc showers from NW to SE later in the day, ushering in next fortified shot of chill in a steadily declining temp regime into the weekend.

The longwave pattern will actually favor recoiling heights northward quickly behind the shortwave on Fri as Srn Canada upper low is absorbed into deepening very strong polar vortex near the pole.  But left behind in fast westerly flow will be new energy ejecting from the Aleutian low, and this will help to maintain cool flow sfc and aloft into New Eng until these cold shortwaves pass later in the weekend.  Thereafter, strong Pacific energy will be trying to close off briefly over the Midwest, and while it may not live long, it will lower heights enough for energy continuing to shoot east from the strengthening Aleutian low - feeding off southward seeping energy from the polar vortex - into this new developing trough.  This feed of air from polar vortex to Aleutian low to Intermountain region will assist in longwave retrogression, with trough settling to our west, and putting NewEng in developing deep SW flow.  This sets up a pattern that will favor both warmth, and rainfall into NewEng for the first half of November, with the warmth coming on by next Mon/Tue, and the moisture not too far behind - likely a decent rain event MidAtl to Northeast mid to late next week as energy continues to eject from base of new trof, carrying Pacific subtropical moisture and tapping Gulf moisture.  Though this results in building northeast warmth thru the first two weeks of November, winter lovers should not lose hope here, as the retrogression will cease and the weather pattern become a bit more progressive by the latter half of the month, largely thanks to a super-ridge to develop across the Nrn Pacific, eventually dislodging both the energy and cold out of Alaska while NewEng warmth should serve as fuel for pumping heights to our east and building a rather impressive block over Greenland the latter half of the month.

So, in the short term we see cold persisting and in fact providing one of our cooler shots thus far for the upcoming weekend - likely to be accompanied by at least some upslope snows - before we see our pattern shift to warmth, then wet and warm...all perhaps en route to a different second half of November.

In the meantime, ski resorts should be able to take advantage of good snowmaking weather most nights except Tue Ngt of this week, through Mon Ngt of next week.  Make the most of it if you want to get the early start on the season, as you'll need a base that can survive only occasional snowmaking capabilities Nov 7 thru 14.

Matt


HEAVY, LOCALLY FLOODING RAIN, DAMAGING WIND, PERIODS OF MOUNTAIN SNOW AND BATTERING WAVES TO MOVE THROUGH NEW ENGLAND THIS WEEKEND...

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

General Weather Summary:

Don't forget the Southern New England Weather Conference, slated for this Saturday, October 28 in Brookline, MA!  Open to ameteurs and professionals, alike, this conference is a great way to stay on top of the latest weather information for New England forecasters.  For more information, click here!

Weatherwise, New England is enjoying a calm and mostly sunny Friday ahead of what will be a powerhouse storm on Saturday.  This storm will bring heavy rain, damaging wind, a period of snow, and large waves to New England this weekend.

We're watching the merger of two strong storms over the Southeastern United States for our Friday, which will merge into a powerhouse storm for New England on Saturday as a third piece of energy becomes involved.  Each of these disturbances have been examined in this discussion over the course of the week - the moisture-packed remnants of what was once Hurricane Paul, the Alaskan energy that brought a blizzard to Colorado on Thursday, and additional energy diving southeast across the Northern Plains.  As of this writing, morning tornadoes have already been reported in the Gulf Coast states as deep tropical moisture funnels northward into the developing storm center.  Closer to home, high pressure (fair weather) has been gradually letting go of the region, but is holding on with enough dry and cool air to bring sunshine, much needed after a morning start in the 20s and 30s!  With a light wind, the chill of the past few days has been significantly muted, and even though actual temperatures will be somewhat cooler than midweek, the presence of sunshine and lack of wind will make a big difference.

Increasing clouds Friday night will come in advance of the approaching major storm, and rains will develop from southwest to northeast - first in Connecticut around midnight, then farther northeast thereafter.  While this storm won't reach peak intensity until over Eastern Canada, it will be undergoing a rapid strengthening phase as it moves over New England on Saturday, which means we'll experience a variety of dynamic weather.

Steady rains will be falling by Saturday at 8 AM through the southwestern half of New England, or a bit more than that, all the way into Western Maine.  This moisture surges north as we're still trying to let go of a stubborn cold airmass and importing a lot of deep tropical warmth and moisture.  The tropical nature of this air will mean it will be quick to erode cold air in most locales, and it will find additional and crucial help from a strengthening southeast flow that comes off Atlantic waters still running well into the 50s.  This marine influenced airmass will penetrate the lower few thousand feet of the atmosphere, and even though temperatures above about 5000 feet will be below freezing at the beginning of the event Saturday morning, the warmth near ground level will be sufficient to melt any ice crystals (snowflakes).  The exception to this early Saturday morning may be in the Northeast Kingdom of Vermont and the higher terrain of the Green Mountains, where snow may begin the event on Saturday morning for an hour or so before changing to rain, and after only a dusting to an inch.  Farther north and east, through the Northern White Mountains and Mountains of Maine, it will be harder to dislodge the cool air, as southeast winds struggle to displace cold air more in these locales, meaning a few hours of snow would be possible in these locales, too, with some accumulation in the higher terrain (especially of Northwest Maine) of anywhere between one and four inches (see map) before a brief change to sleet, then to all rain.  Even farther north, the precipitation won't arrive until later in the day Saturday but cold air will likely hold on long enough for a period of snow here, too, in Northern Maine.

Sfx_accums_00000 So where does that leave us farther south?  Most of New England will rain quite hard with this Saturday storm, as the primary storm cuts west of New England, but a slight reflection develops as a secondary storm from Virginia in the morning to Eastern New England in the afternoon.  Winds will ramp up along coastal locales where gusts to or over 50 mph will be possible Saturday afternoon, and gusts to 70 mph will be possible Saturday evening along the middle and Downeast coasts of Maine!  Winds of this velocity would be sufficient to cause damage to trees and powerlines, as well as blow around lightweight objects and destroy Halloween decorations through the day Saturday, especially within 30 miles of all New England coastlines, and the risk of power outages would be heightened in these areas.  With the exceptionally intense gusts along the Maine coast, shingle damage may be done to some immediate coastal residences.

Sfx_wind_fcst_near_sfc_00000 Sfx_wind_fcst_near_sfc1

Additionally, the infusion of tropical moisture to a lingering cool fall airmass will mean a strong clash of different airmasses that will crank out heavy rain across all of New England with at least one to two inches in most areas, though more along the lines of two to three inches of rain through the interior of Central and Southern New England!  This much rain will fall in roughly a 12 hour period on Saturday, timed right in the heart of the day, and would be enough to prompt at least minor flooding of streams, along with ponding of water in poor drainage areas, including areas where catch basins are clogged with leaves.  Runoff may even result in some small rivers experiencing minor flooding by Sunday morning.

Sfx_precip_fcst_00000

This major storm will churn the ocean waters, as well, and mariners will not want to be caught out in this storm on Saturday, with large swell lingering into Sunday as seas build 15-20 feet on Saturday, and linger at 10-15 feet on Sunday.

As for the weather across New England on Sunday, our powerful storm will have pulled over the border into Eastern Canada, but will grow quite large.  This will mean an expanding wind field under the belly of the storm, with brisk winds for all of New England gusting to 45 miles per hour (stronger in the mountains and hills where damage will still be possible) and snow showers across the mountains of the North where moisture and cold air will both wrap underneath the storm and cross the Canadian border.  Elsewhere in New England, the chill of the cool breeze will at least be muted somewhat by sunshine mixed with plenty of puffy cumulus clouds.  Nonetheless, the day should be redeemable in many areas after a virtual loss on Saturday.

Cold air will already be battled aloft by incoming warmth on Monday, and this is likely to bring a few clouds through the day, possibly producing a few isolated showers.  Milder air will make a surge north for Tuesday before another shot of chill sends the remainder of the week back to below normal temperatures.

Technical Discussion:  None today, believe it or not...but I think we've sufficiently addressed the storm thru prior techie discussions (below) and the maps/discussion above.  Enjoy the storm, techies!

Matt

Matt's Technical Meteorological Discussion:  Updated Thursday, October 26 at 2:45 PM

Plenty put down here yesterday (see below) and crunched for time today so will keep this rather brief.  Decoupling tonight with winds slackening and high building in.  Dewpoints have been lowering thru the day and this dry air will allow temps to fall quickly after dark with widespread frost.  Cold start Fri AM will be moderated by sunshine tho sfc ridge is overhead which means axis of chilly air overhead and mixing limited thanks to subsidence inversion, which will limit temp rise and keep max temps around or perhaps even a degree or two cooler than Thu, even tho drier ambient air will increase amount of insolation.  Reports from Nrn VT indicate no sun all week...will try to get some peeks of sun out with mixing on Fri.

Weekend storm will be a doozie...remains to be seen just how fast it strengthens but looking at minimum of a 12-14 mb drop from Ern VA 12Z Sat to Ern MA 00Z Sun, and perhaps more strengthening than that, which will both crank winds ahead of the circulation, cause banding of precip, and result in ageostrophic wind N of the storm.  Winds fcstd to crank to 70 kts over Srn Gulf of ME at 925 mb...and gusts over 60 will be likely from Nrn MA coast thru ME coast Sat afternoon.  Seas churn to 15-20 feet as a result.  Baroclinic zone discussed yesterday still looks like important player in focusing rainfall which will be heaviest thru interior and 2"-3" likely in large swath with closer to 2" elsewhere and lesser amounts NW.  As for the ageostrophic flow, that is the toughest part of the fcst wtih regard to ptype and tho it is not modeled by guidance, a rapidly strengthening storm would turn a fcstd E/ESE wind to a NE wind over Aroostook Cty ME and that's my concern for extended wintry precip there.  Elsewhere, Greens and Whites both shud have enuf cold air in place on commencement of precip for wintry burst, with Whites thru ME Mountains seeing slowest erosion of cold dome that historically would lead to some accum before a mix and change to sleet, then eventually rain as the cold is overwhelmed.

3" in 12 hrs enuf to aggravate streams and drains clogged with leaves will make many areas of poor drainage on Sat.  Cold air to wrap around belly of storm Sat Ngt/Sun with snow showers in Nrn NewEng and upslope heavier snows Nrn Greens/Whites/NW ME mountains.  Below normal pattern holds thru next week.

More detail for public consumption above in General Wx Summary.

Matt

Wednesday's Discussion:

2:20 PM:  Winds kicking up on cue across NewEng this afternoon and with gusts to over 30 mph at times, this is especially raw across Nrn VT where rain showers have been lingering beneath cold pool and with assistance of upslope flow.  Remainder of north seeing sct rain and snow showers with multiple weak vorts and localized upslope flow, along with lingering instability thanks to cold air aloft.  Conditions stay similar overnight but without diurnal disruption due to thermally induced mixing, and this will allow revitalization of upslope areas of snow showers, where some light accumulation is possible on the order of 1-3" for higher terrain - esp above 1200-1400 feet from VT to NH/ME as profile is colder over VT.  In fact, below freezing profile reaches 900-1000 feet in Nrn Greens by predawn Thu.

Overall trend for slower progression of weather pattern offsets a few parts of the forecast for us, starting with Thu when more clouds will linger below sluggish cold pool, then for Fri when we can extend dry weather thru the day with increasing clouds late.

Yesterday's thoughts on the weekend storm focused upon Dr. Colucci's "always beware the col" and the belief that this upcoming storm would take a track southeast of NewEng toward the well-defined col.  00Z GFS and Canadian Ensembles have both come back with eastward leaning solutions, but there are plenty of factors that need to be considered in this forecast for NewEng.  First of all, let's understand what's going on in the longwave pattern, and that is the combination of two big factors: 1) The continued and, in fact, accelerated breakdown of the Greenland block that has been in place, and 2) a large amount of Alaskan energy ejecting from the Aleutian low (which has shifted N recently in response to Siberian input) and diving into the mean trof position which begins W of NewEng but comes directly overhead given these two major factors at play.  What's to be truly amazing come Friday is the interaction of systems that take part in this longwave redefinition, which includes 1) Pacific energy sliding into the Pac NW currently that will carry a primary low well to our west, 2) the remnants of what was Hurricane Paul, coming across TX and tapping the Gulf for copious amounts of moisture and a storm center chock full of latent heat expenditure, and 3) the aforementioned Siberian/Alaskan energy combo that slides quickly SE in the fast Westerlies and is the final addition to prompt a negative tilt of a wildly amplifying trough.  Diffluence ahead of this system will be quite impressive aloft on Saturday over the waters south of NewEng, and this, coupled with tight baroclinic zone and aforementioned col will aid in steering quickly strengthening storm over the waters S and SE of NewEng on Sat, to a position N of NewEng where the low will become vertically stacked and bomb over Ern Canada, ensuring very windy conditions across the Northeast on Sun/Mon, though without much available deep cold (we've expended a large chunk of it already and there is currently no well of deep cold available in the Northern Hemisphere) it's unlikely we'll find more than a shallow surface dome of cold moving in, which will mix enough diurnally to warm on Sun and Mon, esp in Srn NewEng where strong wind is also downsloping wind.

We'll pick that thought up again in a moment, but before we get too far ahead of ourselves it's important to cover more details on the events that will transpire with the weekend storm itself.  We left off with storm track, likely to be S and SE of NewEng before hooking N as the surface center is pulled beneath the upper low and bombs as a result.  The question of the last few days has been just how much cold air holds on with the approach of the storm, and what ptype we're looking at for whom.  There remains little doubt that this event will be a liquid event for Central and Southern New England, where 850 temp anomalies of +2 to +6 C move in ahead of storm thanks to tropical input from remnants of Paul.  This is where it's important to keep in mind the origins of a storm, which I often will refer to in these technical discussions, as airmass origin can and does make a difference later down the line.  With so much tropical air available, it's quite likely there will be a slug of midlvl warmth that will be nearly impossible to stop without deep cold, of which we'll be out of when the moisture arrives.  The warm advection will be so intense that it's likely to overtake most of NewEng with warm air as the storm pushes N on Sat.  That's not the end of the story, however, as warm and moist advection means the influx of higher potential temperature air, which will create isentropic lift.  Strong enough isentropic lift will aid in dynamic (adiabatic) cooling, which will in turn hold a colder atmospheric profile.  Yesterday I noted the presence of a surface anticyclone in Eastern Canada that would serve to hold the low level cold into Nrn NewEng for me to consider significant snows in the mountains of the North, though the slowing of the pattern has allowed this high to weaken as upper level diffluence lifts north Fri night into Sat, which means we've lost the mechanism originally in place to hold the cold, and all we can count on for wintry precip is old, diminishing low level cold and dynamic cooling.  The end result of this should be a burst of snow in the mountains of Maine, especially, and perhaps in Northern Maine to begin the storm.  With a northeast surface wind ahead of the storm center thru most of Sat, until the passage of the occluded front connecting the primary low over Ontario with the secondary low swinging northward, east of NewEng, we are likely to hold the surface cold into esp mountain valleys in Maine, but the warm surge aloft in the midlvls (750-600 mb) assoc with the tropical moisture should be too strong to hold off, and ptype will swing to rain even thru most of ME later Sat, tho perhaps could hold as sleet for a time in the mountain valleys.

Elsewhere, heavy rain and strong wind will be the features of the strengthening low, with a well-established tropical moisture tap loading the system and intense dynamics assisting in wringing this moisture out, esp along low and midlvl baroclinic zone that lifts across interior NewEng where banded heavy precip is most likely.  Given high precipitable water values, should be able to exceed current guidance and crank out 2"-3" liquid QPF for these interior locales - even though most of the QPF comes with the slug of warm advection, this still lasts a good 12 hours during Sat.  Potent low level jet will crank ahead of this storm and this will translate to strong sfc winds near the storm center along Eastern Coastlines from the E on Sat...perhaps beginning NE but then will have to come E or even SE as this low pressure center is developing as secondary/triple point along occluded front.

As the storm pulls away Sat Ngt/Sun, mentioned above that storm deepens rapidly and winds kick, but lack of deep cold thanks to lack of strong anticyclone means no rapid surge of cold for all of NewEng, though low level cold will be intense enuf in Nrn NewEng to turn ptype to snow and snow may come down hard in Nrn ME during this period as wraparound comma head will come all the way under belly of circulation...biggest question here is whether it misses just north of ME or delivers a windswept snow to Nrn Aroostook County, which is possible on Sun.  Farther southwest, upslope flow will be maximized in mountains of ME on Sun, but lots of instability Cu will layer the skies of NewEng with snow showers in most of the mountainous terrain.  As the upper low churns over Ern Canada, it essentially creates its own pool of cold air courtesy of dynamic cooling, and this cool pool settles over NewEng middle to end of next week, and though it is progged to be at least 8 C anomalously cold at 850, the shallow nature of the cold is likely to allow mixing and therefore modify the impact somewhat, though clearly below to much below normal temp regime will continue.

Matt

Tuesday Discussion:

1:10 PM:  No techie update yesterday thanks to server failure at provider - apologies, especially considering I'm off to a public appearance today so limited time to share my thoughts.  Let me get them out as quickly as possible:

Well defined vort max to swing southeast across VT/NH/ME overnight and into early Wed AM.  The cyclonic vorticity advection (CVA) ahead of this vort is fairly well distributed - largely normal to the flow - and that will provide extra impetus to generate convective precip overnight.  Couple this with cold air aloft providing instability and upslope flow in Nrn mountains and you have a fairly favorable setup for accumulating snow even though sfc winds may not be the ideal NW direction I'd like to see.  Nonetheless, 925 mb temps fall steadily late this afternoon thru Tue Ngt and this shud ensure elevated areas are cold enuf for snow.  To take thermal fcst profiles literally, no snow will fall below 1500 feet, but I'd expect the convective nature of the precip in the CVA ahead of the vort max to overcome this inhibiting factor and lower the snow level considerably.  Elevated terrain will benefit from the combo of cold profile, abundant moisture, good snow crystal growth and upslope flow to crank out amounts as high as 6"-8" in favored locales like Jay Peak and perhaps Sugarloaf, as well.  Enuf warm air in the valleys that locales below 500-600 feet will probably have trouble getting snow to stick well as sfc temps stay above freezing.  Still, vort max passage doesn't occur until Wed AM in Srn NH and near coastal plain of ME where some snowflakes certainly may mix in, and wouldn't want this to be a shock to the awakening public in the AM so have adlibbed this possibility accordingly.  Have carried D-1" rather far south, as well, but am stressing elevation dependence - bottom line here is that I'm untrusting of the pattern with the combo of instability and vorticity, I'm untrusting of the low-level wind flow that is not only non-ideal upslope north, but more importantly to this point is non-ideal downslope south, and I'm untrusting of moist low levels.  Nonetheless, anything that does survive the trip would die or ship out quickly Wed as a final mix of mostly raindrops and some snowflakes, tho upslope flow will strengthen on Wed in the Nrn mountains where snow showers will continue.  Let's also not forget the connection from Lake Ontario, which has dropped light rain showers in SW CT earlier today and tho it has broken up with diurnal htg and assoc mixing, should redevelop overnight tho will be warm enuf for rain in these areas.

Moisture mixes out a bit better on Wed but cold pool is slow to decay and while I expect more sunshine, more mixing, greater wind speeds than Tue, clouds will still bubble aplenty during the afternoon beneath the cool pool.  Thu is a decent break in the action, and the trend has been for slower progression of Fri system which makes sense for at least a little while as Pacific energy and Tropical Storm Paul merge in the trof over the SE US.  This significant amplification will slow the progression, but once Paul's remnants are absorbed into the circulation, this will enhance the thrust of warm and moist advection ahead of the storm, and precip should develop later Fri from SW to NE.  1020 mb bubble of high pressure over Ern Canada bridges to high pressure over MidAtl while col (area of light wind) sets up between these two anticyclones and the cyclones to the southwest and northeast of NewEng.  At Cornell University, one of my meteorology professors, Dr. Colucci always would say "always beware the col".  As the low level flow becomes weakly convergent in this coll, it serves as a magnet for secondary storm development and/or track, and the GFS is close to this line of thinking.  A track from the MidAtl coast to the col for a secondary low would allow cool air to hold into Nrn NewEng enuf for a significant accumulating snow event Fri Ngt into Sat and am carrying that in fcst for now, with liquid much more likely ptype in Srn NewEng.

Enjoy your day.

Matt


TWO DAYS OF CALM...STORM TO RAGE ACROSS NEW ENGLAND SATURDAY

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

General Weather Summary:

Maintenance Note:  Radar links at right have been experiencing outages due to technical problems with the national server at the National Weather Service.  Even though the images may or may not be present when you're here, the links are still active and should be repaired before too long.

Weather:  As we stare down the barrel of another major storm for New England for the start of the weekend, we have two decent days to enjoy - nice days for those of us who can look at it from inside the car, house or office, but still a bit of chill for those of us who work outside through the day.

Thursday began with sunshine and cool temperatures for many, though clouds and a few showers still lingered in especially the Green Mountains, where folks in the state capital of Vermont began the day at 35 degrees with rain showers - ouch!  Elsewhere, sunshine will warm the atmosphere a bit today, though the drier air that helps to bring a bit more sunshine out also is cooler in nature, and temperatures will still fall either side of 50.  That said, winds will be relaxing on Thursday with only a few gusts over 20 mph as opposed to Wednesday's gusts in excess of 30 mph.  Still, for those of us who spend an extended period of time outside, the breeze will add a decided chill to the air.

The nation's weather map puts a strong area of low pressure in the Central Plains, which has delivered quite a snowstorm to the Rocky Mountains, a leading surge of moisture with showers and downpours near Chicago, and an eastward migrating slice of high pressure (fair weather) moving toward the East Coast.  The elongated area of high pressure will move over New England Thursday night into Friday, bringing clearing skies, slackening winds, and seeping deeper cool air into New England, allowing temperatures to bottom out in the 20s and 30s for all of New England with widespread frosty conditions by Friday morning.  Though sunshine will come thanks to the dry air associated with this fair weather cell on Friday, the heart of cool air will be in place, and this means highs will struggle to get much above 50 in many areas, and only barely exceed it in others - still well below normal for the date.  Nonetheless, with much lighter winds the air will likely feel a bit more comfortable for most of us.

Increasing clouds Friday night will come in advance of what will end up as a major storm across New England for Saturday.  If you've been reading earlier in the week, you'll remember that this storm is the result of a merger of several disturbances that all bring a significant ingredient to the table for the recipe of a strong storm.  Showers and thunderstorms across the Southeastern United States, and a piece of the rain that postponed last night's World Series game in St. Louis, come as the remnants of what was once Hurricane Paul makes its way across the Southern tier of states.  Though this cluster of showers and thunderstorms is no longer a well defined storm, its origins in the Tropical Pacific mean it comes packed with a combination of significant moisture and with plentiful heat energy.  Also traversing the country is a disturbance I've been following through the week that began in the Pacific and made its way through the Northwestern United States, now producing heavy snow in a winter storm at the time of this writing over the Rocky Mountains.  Finally, ready to enter the picture over the Northern Plains is additional strong and cold energy that's been moving across Canada - of Siberian origin and providing a shot in the arm for storm development.  Eventually, these three major disturbances will all merge to form an amazing storm, and while this storm won't reach peak intensity until over Eastern Canada, it will be undergoing a rapid strengthening phase as it moves over New England on Saturday.

With the approach of this storm, increasing clouds Friday night will lead to steady rains developing by Saturday at 8 AM through the southwestern half of New England.  A challenge for meteorologists will be what type of precipitation falls where as the moisture moves in, largely because we'll be letting go of a stubborn cold airmass and importing a lot of deep tropical warmth and moisture.  The tropical nature of this air will mean it will be quick to erode cold air in most locales, and it will find additional and crucial help from a strengthening southeast flow that comes off Atlantic waters still running well into the 50s.  This marine influenced airmass will penetrate the lower few thousand feet of the atmosphere, and even though temperatures above about 5000 feet will be below freezing at the beginning of the event Saturday morning, the warmth near ground level will be sufficient to melt any ice crystals (snowflakes).  The exception to this early Saturday morning may be in the Northeast Kingdom of Vermont and the higher terrain of the Green Mountains, where snow may begin the event on Saturday morning for a few hours before changing to rain.  Farther north and east, through the Northern White Mountains and Mountains of Maine, it will be harder to dislodge the cool air, as southeast winds struggle to displace cold air more in these locales, meaning a few hours of snow would be possible in these locales, too, with some accumulation in the higher terrain (especially of Northwest Maine) before a brief change to sleet, then to all rain.  Farther north, still, the precipitation won't arrive until later in the day Saturday but cold air will likely hold on long enough for a period of snow here, too, in Northern Maine.  In fact, the next 24 hours will be critical in putting my finger on just how quickly warm air can really move into Northern Maine, where it would seem to me that a rapidly deepening storm over Southern New England should turn winds to the northeast in Northern Maine, holding cold air in longer and thereby increasing the duration of snow and potential accumulations, which would be able to reach plowable amounts.

So where does that leave us farther south?  Most of New England will rain quite hard with this Saturday storm, and as it strengthens very quickly from Virginia in the morning to Eastern New England in the afternoon, winds will ramp up along coastal locales where gusts to or over 50 mph will be possible Saturday afternoon!  Additionally, the infusion of tropical moisture to a lingering cool fall airmass will mean a strong clash of different airmasses that will crank out heavy rain across all of New England with one to two inches in most areas, and more along the lines of two to three inches of rain through the interior of Central and Southern New England!  This much rain will fall in roughly a 12 hour period on Saturday, timed right in the heart of the day, and would be enough to prompt at least minor flooding of streams, along with ponding of water in poor drainage areas, including areas where catch basins are clogged with leaves.

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This major storm will churn the ocean waters, as well, and mariners will not want to be caught out in this storm on Saturday, with large swell lingering into Sunday as seas build 15-20 feet on Saturday, and linger at 10-15 feet on Sunday.

As for the weather across New England on Sunday, our powerful storm will have pulled over the border into Eastern Canada, but will grow quite large.  This will mean an expanding wind field under the belly of the storm, with brisk winds for all of New England and snow showers across the mountains of the North where moisture and cold air will both wrap underneath the storm and cross the Canadian border.  In the Northern tip of Maine, it's possible we'll remain under a wraparound band of snow, though it will be a matter of tens of miles as to whether we're under this accumulating snow band or just south of it and I'll continue to keep an eye on this potential.  Elsewhere in New England, the cool breeze will at least be muted somewhat by sunshine mixed with plenty of puffy cumulus clouds.  Nonetheless, the day should be redeemable in many areas after a virtual loss on Saturday.

Cold air will already be battled aloft by incoming warmth on Monday, and this is likely to bring thickening clouds later in the day, possibly producing a few showers by late Monday, as well.  The remainder of next week will continue to bring below-normal temperatures!

I'll keep you posted on the storm as we draw closer to it - in the meantime, enjoy the quieter weather Thursday and Friday.

Matt

Matt's Technical Meteorological Discussion:  Updated Thursday, October 26 at 2:45 PM

Plenty put down here yesterday (see below) and crunched for time today so will keep this rather brief.  Decoupling tonight with winds slackening and high building in.  Dewpoints have been lowering thru the day and this dry air will allow temps to fall quickly after dark with widespread frost.  Cold start Fri AM will be moderated by sunshine tho sfc ridge is overhead which means axis of chilly air overhead and mixing limited thanks to subsidence inversion, which will limit temp rise and keep max temps around or perhaps even a degree or two cooler than Thu, even tho drier ambient air will increase amount of insolation.  Reports from Nrn VT indicate no sun all week...will try to get some peeks of sun out with mixing on Fri.

Weekend storm will be a doozie...remains to be seen just how fast it strengthens but looking at minimum of a 12-14 mb drop from Ern VA 12Z Sat to Ern MA 00Z Sun, and perhaps more strengthening than that, which will both crank winds ahead of the circulation, cause banding of precip, and result in ageostrophic wind N of the storm.  Winds fcstd to crank to 70 kts over Srn Gulf of ME at 925 mb...and gusts over 60 will be likely from Nrn MA coast thru ME coast Sat afternoon.  Seas churn to 15-20 feet as a result.  Baroclinic zone discussed yesterday still looks like important player in focusing rainfall which will be heaviest thru interior and 2"-3" likely in large swath with closer to 2" elsewhere and lesser amounts NW.  As for the ageostrophic flow, that is the toughest part of the fcst wtih regard to ptype and tho it is not modeled by guidance, a rapidly strengthening storm would turn a fcstd E/ESE wind to a NE wind over Aroostook Cty ME and that's my concern for extended wintry precip there.  Elsewhere, Greens and Whites both shud have enuf cold air in place on commencement of precip for wintry burst, with Whites thru ME Mountains seeing slowest erosion of cold dome that historically would lead to some accum before a mix and change to sleet, then eventually rain as the cold is overwhelmed.

3" in 12 hrs enuf to aggravate streams and drains clogged with leaves will make many areas of poor drainage on Sat.  Cold air to wrap around belly of storm Sat Ngt/Sun with snow showers in Nrn NewEng and upslope heavier snows Nrn Greens/Whites/NW ME mountains.  Below normal pattern holds thru next week.

More detail for public consumption above in General Wx Summary.

Matt

Wednesday's Discussion:

2:20 PM:  Winds kicking up on cue across NewEng this afternoon and with gusts to over 30 mph at times, this is especially raw across Nrn VT where rain showers have been lingering beneath cold pool and with assistance of upslope flow.  Remainder of north seeing sct rain and snow showers with multiple weak vorts and localized upslope flow, along with lingering instability thanks to cold air aloft.  Conditions stay similar overnight but without diurnal disruption due to thermally induced mixing, and this will allow revitalization of upslope areas of snow showers, where some light accumulation is possible on the order of 1-3" for higher terrain - esp above 1200-1400 feet from VT to NH/ME as profile is colder over VT.  In fact, below freezing profile reaches 900-1000 feet in Nrn Greens by predawn Thu.

Overall trend for slower progression of weather pattern offsets a few parts of the forecast for us, starting with Thu when more clouds will linger below sluggish cold pool, then for Fri when we can extend dry weather thru the day with increasing clouds late.

Yesterday's thoughts on the weekend storm focused upon Dr. Colucci's "always beware the col" and the belief that this upcoming storm would take a track southeast of NewEng toward the well-defined col.  00Z GFS and Canadian Ensembles have both come back with eastward leaning solutions, but there are plenty of factors that need to be considered in this forecast for NewEng.  First of all, let's understand what's going on in the longwave pattern, and that is the combination of two big factors: 1) The continued and, in fact, accelerated breakdown of the Greenland block that has been in place, and 2) a large amount of Alaskan energy ejecting from the Aleutian low (which has shifted N recently in response to Siberian input) and diving into the mean trof position which begins W of NewEng but comes directly overhead given these two major factors at play.  What's to be truly amazing come Friday is the interaction of systems that take part in this longwave redefinition, which includes 1) Pacific energy sliding into the Pac NW currently that will carry a primary low well to our west, 2) the remnants of what was Hurricane Paul, coming across TX and tapping the Gulf for copious amounts of moisture and a storm center chock full of latent heat expenditure, and 3) the aforementioned Siberian/Alaskan energy combo that slides quickly SE in the fast Westerlies and is the final addition to prompt a negative tilt of a wildly amplifying trough.  Diffluence ahead of this system will be quite impressive aloft on Saturday over the waters south of NewEng, and this, coupled with tight baroclinic zone and aforementioned col will aid in steering quickly strengthening storm over the waters S and SE of NewEng on Sat, to a position N of NewEng where the low will become vertically stacked and bomb over Ern Canada, ensuring very windy conditions across the Northeast on Sun/Mon, though without much available deep cold (we've expended a large chunk of it already and there is currently no well of deep cold available in the Northern Hemisphere) it's unlikely we'll find more than a shallow surface dome of cold moving in, which will mix enough diurnally to warm on Sun and Mon, esp in Srn NewEng where strong wind is also downsloping wind.

We'll pick that thought up again in a moment, but before we get too far ahead of ourselves it's important to cover more details on the events that will transpire with the weekend storm itself.  We left off with storm track, likely to be S and SE of NewEng before hooking N as the surface center is pulled beneath the upper low and bombs as a result.  The question of the last few days has been just how much cold air holds on with the approach of the storm, and what ptype we're looking at for whom.  There remains little doubt that this event will be a liquid event for Central and Southern New England, where 850 temp anomalies of +2 to +6 C move in ahead of storm thanks to tropical input from remnants of Paul.  This is where it's important to keep in mind the origins of a storm, which I often will refer to in these technical discussions, as airmass origin can and does make a difference later down the line.  With so much tropical air available, it's quite likely there will be a slug of midlvl warmth that will be nearly impossible to stop without deep cold, of which we'll be out of when the moisture arrives.  The warm advection will be so intense that it's likely to overtake most of NewEng with warm air as the storm pushes N on Sat.  That's not the end of the story, however, as warm and moist advection means the influx of higher potential temperature air, which will create isentropic lift.  Strong enough isentropic lift will aid in dynamic (adiabatic) cooling, which will in turn hold a colder atmospheric profile.  Yesterday I noted the presence of a surface anticyclone in Eastern Canada that would serve to hold the low level cold into Nrn NewEng for me to consider significant snows in the mountains of the North, though the slowing of the pattern has allowed this high to weaken as upper level diffluence lifts north Fri night into Sat, which means we've lost the mechanism originally in place to hold the cold, and all we can count on for wintry precip is old, diminishing low level cold and dynamic cooling.  The end result of this should be a burst of snow in the mountains of Maine, especially, and perhaps in Northern Maine to begin the storm.  With a northeast surface wind ahead of the storm center thru most of Sat, until the passage of the occluded front connecting the primary low over Ontario with the secondary low swinging northward, east of NewEng, we are likely to hold the surface cold into esp mountain valleys in Maine, but the warm surge aloft in the midlvls (750-600 mb) assoc with the tropical moisture should be too strong to hold off, and ptype will swing to rain even thru most of ME later Sat, tho perhaps could hold as sleet for a time in the mountain valleys.

Elsewhere, heavy rain and strong wind will be the features of the strengthening low, with a well-established tropical moisture tap loading the system and intense dynamics assisting in wringing this moisture out, esp along low and midlvl baroclinic zone that lifts across interior NewEng where banded heavy precip is most likely.  Given high precipitable water values, should be able to exceed current guidance and crank out 2"-3" liquid QPF for these interior locales - even though most of the QPF comes with the slug of warm advection, this still lasts a good 12 hours during Sat.  Potent low level jet will crank ahead of this storm and this will translate to strong sfc winds near the storm center along Eastern Coastlines from the E on Sat...perhaps beginning NE but then will have to come E or even SE as this low pressure center is developing as secondary/triple point along occluded front.

As the storm pulls away Sat Ngt/Sun, mentioned above that storm deepens rapidly and winds kick, but lack of deep cold thanks to lack of strong anticyclone means no rapid surge of cold for all of NewEng, though low level cold will be intense enuf in Nrn NewEng to turn ptype to snow and snow may come down hard in Nrn ME during this period as wraparound comma head will come all the way under belly of circulation...biggest question here is whether it misses just north of ME or delivers a windswept snow to Nrn Aroostook County, which is possible on Sun.  Farther southwest, upslope flow will be maximized in mountains of ME on Sun, but lots of instability Cu will layer the skies of NewEng with snow showers in most of the mountainous terrain.  As the upper low churns over Ern Canada, it essentially creates its own pool of cold air courtesy of dynamic cooling, and this cool pool settles over NewEng middle to end of next week, and though it is progged to be at least 8 C anomalously cold at 850, the shallow nature of the cold is likely to allow mixing and therefore modify the impact somewhat, though clearly below to much below normal temp regime will continue.

Matt

Tuesday Discussion:

1:10 PM:  No techie update yesterday thanks to server failure at provider - apologies, especially considering I'm off to a public appearance today so limited time to share my thoughts.  Let me get them out as quickly as possible:

Well defined vort max to swing southeast across VT/NH/ME overnight and into early Wed AM.  The cyclonic vorticity advection (CVA) ahead of this vort is fairly well distributed - largely normal to the flow - and that will provide extra impetus to generate convective precip overnight.  Couple this with cold air aloft providing instability and upslope flow in Nrn mountains and you have a fairly favorable setup for accumulating snow even though sfc winds may not be the ideal NW direction I'd like to see.  Nonetheless, 925 mb temps fall steadily late this afternoon thru Tue Ngt and this shud ensure elevated areas are cold enuf for snow.  To take thermal fcst profiles literally, no snow will fall below 1500 feet, but I'd expect the convective nature of the precip in the CVA ahead of the vort max to overcome this inhibiting factor and lower the snow level considerably.  Elevated terrain will benefit from the combo of cold profile, abundant moisture, good snow crystal growth and upslope flow to crank out amounts as high as 6"-8" in favored locales like Jay Peak and perhaps Sugarloaf, as well.  Enuf warm air in the valleys that locales below 500-600 feet will probably have trouble getting snow to stick well as sfc temps stay above freezing.  Still, vort max passage doesn't occur until Wed AM in Srn NH and near coastal plain of ME where some snowflakes certainly may mix in, and wouldn't want this to be a shock to the awakening public in the AM so have adlibbed this possibility accordingly.  Have carried D-1" rather far south, as well, but am stressing elevation dependence - bottom line here is that I'm untrusting of the pattern with the combo of instability and vorticity, I'm untrusting of the low-level wind flow that is not only non-ideal upslope north, but more importantly to this point is non-ideal downslope south, and I'm untrusting of moist low levels.  Nonetheless, anything that does survive the trip would die or ship out quickly Wed as a final mix of mostly raindrops and some snowflakes, tho upslope flow will strengthen on Wed in the Nrn mountains where snow showers will continue.  Let's also not forget the connection from Lake Ontario, which has dropped light rain showers in SW CT earlier today and tho it has broken up with diurnal htg and assoc mixing, should redevelop overnight tho will be warm enuf for rain in these areas.

Moisture mixes out a bit better on Wed but cold pool is slow to decay and while I expect more sunshine, more mixing, greater wind speeds than Tue, clouds will still bubble aplenty during the afternoon beneath the cool pool.  Thu is a decent break in the action, and the trend has been for slower progression of Fri system which makes sense for at least a little while as Pacific energy and Tropical Storm Paul merge in the trof over the SE US.  This significant amplification will slow the progression, but once Paul's remnants are absorbed into the circulation, this will enhance the thrust of warm and moist advection ahead of the storm, and precip should develop later Fri from SW to NE.  1020 mb bubble of high pressure over Ern Canada bridges to high pressure over MidAtl while col (area of light wind) sets up between these two anticyclones and the cyclones to the southwest and northeast of NewEng.  At Cornell University, one of my meteorology professors, Dr. Colucci always would say "always beware the col".  As the low level flow becomes weakly convergent in this coll, it serves as a magnet for secondary storm development and/or track, and the GFS is close to this line of thinking.  A track from the MidAtl coast to the col for a secondary low would allow cool air to hold into Nrn NewEng enuf for a significant accumulating snow event Fri Ngt into Sat and am carrying that in fcst for now, with liquid much more likely ptype in Srn NewEng.

Enjoy your day.

Matt


AS NEW ENGLAND BREEZES BLOW WEDNESDAY...WE CAREFULLY EYE A MAJOR STORM SET TO DEVELOP TO OUR WEST

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

General Weather Summary:

Tuesday night and Wednesday morning snow was quite limited in scope across the Northern reaches of New England, falling only in the highest terrain of Vermont, New Hampshire and Maine as moisture found only limited focus ahead of our early Wednesday disturbance, largely due to a uni-directional wind - that is, not much of a wind shift to crank out the moisture.  Nonetheless, our active weather pattern will continue for the next several days into the weekend, and will bring another strong storm by Friday night.  Meanwhile, the same large storm in the upper levels continues to park a pool of cool air over New England, favoring development of puffy cumulus clouds and a few showers of rain and snow.

While the passage of the upper level disturbance and an associated wind shift at the surface brought anywhere from a trace to 3" of snow to the higher terrain - and FAR less snow than I anticipated to high terrain at the Canadian border of northeastern Vermont (valleys remained warmer and saw rain, as expected) - it should still succeed in carrying increased wind gusts and continued chilly air to most of New England, and a follow-up disturbance will move into the North Country tonight, adding to storm totals in areas that thus far have fallen short.  Though some snow and rain showers will linger into early afternoon around the Champlain Valley, the higher terrain of the White Mountains and Maine Mountains, and in Eastern Maine, most areas will find a blend of sun and large, puffy cumulus clouds that will drop only a few sprinkles or light rain showers from time to time, with the balance of the day staying dry for most of New England.  Winds will blow out of the west-northwest, gusting to over 30 mph at times under the belly of the mature storm east of New England. 

By Wednesday night, yet another weak disturbance will move through Northern New England aloft, and snow showers will find new life across the high terrain of the north.  With slightly colder air in place, the rain/snow line will likely drop lower in elevation than it was Tuesday night - perhaps to around 900 feet in Vermont and 1300 feet in New Hampshire and Maine, though accumulations would be rather light in most areas.  Elsewhere, expect a chilly night Wednesday night with winds subsiding a bit, though still breezy especially early.  Thursday will bring another cool blend of sunshine and billowing clouds - a break in the action before our weather turns stormy once again.

This end-of-week storm comes with a history, as two key weather systems will come together in its formation.  The first is what was once Hurricane Paul, crossing Mexico as a large mass of moisture, heat and energy heading for Texas en route to the southeastern United States, carried by the subtropical jet stream.  To the north, a strong energetic disturbance is moving southeast down the Western Canada coastline, caught in the polar jet stream that carries energy centers and cold air from the north.  This storm, too, will dive toward the Southeastern U.S., where it will meet with the remnants of Paul late in the week.  In the early stages of the merger, snows will develop in the Rockies where Winter Storm Warnings are in effect, and heavy rains will likely jeopardize the World Series game Wednesday night in St. Louis.

The strengthening storm to the southwest of New England on Thursday will launch a slug of meaningful warmth and moisture toward New England late Friday.  Ahead of this slug of moisture, most of Friday should remain dry with increasing clouds late in the day as a split area of high pressure defines warmer air to the south and cool air to the north in Canada, but holds the moisture at bay.  The Canadian fair weather cell packed with cool air will be settling north of New England later Friday, and this will provide a weak supply of cold air to New England.  The result will be a stubborness of the cold air to let go from Northern New England as moisture comes streaming in, and this likely will crank out at least some snow across Northern New England when precipitation moves into New England Friday night into Saturday, and perhaps into Sunday as well.  Though this will be a concern in the mountains of the North - where a mix of many types of precipitation are likely this weekend with an elevation dependency - most of New England will find a windswept rain Friday night into Saturday, as the storm center moving out of the Southeastern United States passes over the waters southeast of New England, holding a northeast wind and therefore very cool air in place. 

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As this storm wraps northeast of New England later Saturday and Sunday, cold air will wrap around the back of the circulation, and this will result in a changeover to wintry precipitation in the north, though there are questions just how much moisture will still be available once the lower elevations of the north (where most of us live) change to snow.  Nonetheless, the potential is there for significant snow in some areas, so this continues to bear watching.  By Sunday, skies will be partly sunny in Central and Southern New England, while snow showers and bursts of snow will linger in the north, with breezy conditions for one and all.

Enjoy your Wednesday.

Matt

Matt's Technical Meteorological Discussion:  Updated Wednesday, October 25 at 2:20 PM

Winds kicking up on cue across NewEng this afternoon and with gusts to over 30 mph at times, this is especially raw across Nrn VT where rain showers have been lingering beneath cold pool and with assistance of upslope flow.  Remainder of north seeing sct rain and snow showers with multiple weak vorts and localized upslope flow, along with lingering instability thanks to cold air aloft.  Conditions stay similar overnight but without diurnal disruption due to thermally induced mixing, and this will allow revitalization of upslope areas of snow showers, where some light accumulation is possible on the order of 1-3" for higher terrain - esp above 1200-1400 feet from VT to NH/ME as profile is colder over VT.  In fact, below freezing profile reaches 900-1000 feet in Nrn Greens by predawn Thu.

Overall trend for slower progression of weather pattern offsets a few parts of the forecast for us, starting with Thu when more clouds will linger below sluggish cold pool, then for Fri when we can extend dry weather thru the day with increasing clouds late.

Yesterday's thoughts on the weekend storm focused upon Dr. Colucci's "always beware the col" and the belief that this upcoming storm would take a track southeast of NewEng toward the well-defined col.  00Z GFS and Canadian Ensembles have both come back with eastward leaning solutions, but there are plenty of factors that need to be considered in this forecast for NewEng.  First of all, let's understand what's going on in the longwave pattern, and that is the combination of two big factors: 1) The continued and, in fact, accelerated breakdown of the Greenland block that has been in place, and 2) a large amount of Alaskan energy ejecting from the Aleutian low (which has shifted N recently in response to Siberian input) and diving into the mean trof position which begins W of NewEng but comes directly overhead given these two major factors at play.  What's to be truly amazing come Friday is the interaction of systems that take part in this longwave redefinition, which includes 1) Pacific energy sliding into the Pac NW currently that will carry a primary low well to our west, 2) the remnants of what was Hurricane Paul, coming across TX and tapping the Gulf for copious amounts of moisture and a storm center chock full of latent heat expenditure, and 3) the aforementioned Siberian/Alaskan energy combo that slides quickly SE in the fast Westerlies and is the final addition to prompt a negative tilt of a wildly amplifying trough.  Diffluence ahead of this system will be quite impressive aloft on Saturday over the waters south of NewEng, and this, coupled with tight baroclinic zone and aforementioned col will aid in steering quickly strengthening storm over the waters S and SE of NewEng on Sat, to a position N of NewEng where the low will become vertically stacked and bomb over Ern Canada, ensuring very windy conditions across the Northeast on Sun/Mon, though without much available deep cold (we've expended a large chunk of it already and there is currently no well of deep cold available in the Northern Hemisphere) it's unlikely we'll find more than a shallow surface dome of cold moving in, which will mix enough diurnally to warm on Sun and Mon, esp in Srn NewEng where strong wind is also downsloping wind.

We'll pick that thought up again in a moment, but before we get too far ahead of ourselves it's important to cover more details on the events that will transpire with the weekend storm itself.  We left off with storm track, likely to be S and SE of NewEng before hooking N as the surface center is pulled beneath the upper low and bombs as a result.  The question of the last few days has been just how much cold air holds on with the approach of the storm, and what ptype we're looking at for whom.  There remains little doubt that this event will be a liquid event for Central and Southern New England, where 850 temp anomalies of +2 to +6 C move in ahead of storm thanks to tropical input from remnants of Paul.  This is where it's important to keep in mind the origins of a storm, which I often will refer to in these technical discussions, as airmass origin can and does make a difference later down the line.  With so much tropical air available, it's quite likely there will be a slug of midlvl warmth that will be nearly impossible to stop without deep cold, of which we'll be out of when the moisture arrives.  The warm advection will be so intense that it's likely to overtake most of NewEng with warm air as the storm pushes N on Sat.  That's not the end of the story, however, as warm and moist advection means the influx of higher potential temperature air, which will create isentropic lift.  Strong enough isentropic lift will aid in dynamic (adiabatic) cooling, which will in turn hold a colder atmospheric profile.  Yesterday I noted the presence of a surface anticyclone in Eastern Canada that would serve to hold the low level cold into Nrn NewEng for me to consider significant snows in the mountains of the North, though the slowing of the pattern has allowed this high to weaken as upper level diffluence lifts north Fri night into Sat, which means we've lost the mechanism originally in place to hold the cold, and all we can count on for wintry precip is old, diminishing low level cold and dynamic cooling.  The end result of this should be a burst of snow in the mountains of Maine, especially, and perhaps in Northern Maine to begin the storm.  With a northeast surface wind ahead of the storm center thru most of Sat, until the passage of the occluded front connecting the primary low over Ontario with the secondary low swinging northward, east of NewEng, we are likely to hold the surface cold into esp mountain valleys in Maine, but the warm surge aloft in the midlvls (750-600 mb) assoc with the tropical moisture should be too strong to hold off, and ptype will swing to rain even thru most of ME later Sat, tho perhaps could hold as sleet for a time in the mountain valleys.

Elsewhere, heavy rain and strong wind will be the features of the strengthening low, with a well-established tropical moisture tap loading the system and intense dynamics assisting in wringing this moisture out, esp along low and midlvl baroclinic zone that lifts across interior NewEng where banded heavy precip is most likely.  Given high precipitable water values, should be able to exceed current guidance and crank out 2"-3" liquid QPF for these interior locales - even though most of the QPF comes with the slug of warm advection, this still lasts a good 12 hours during Sat.  Potent low level jet will crank ahead of this storm and this will translate to strong sfc winds near the storm center along Eastern Coastlines from the E on Sat...perhaps beginning NE but then will have to come E or even SE as this low pressure center is developing as secondary/triple point along occluded front.

As the storm pulls away Sat Ngt/Sun, mentioned above that storm deepens rapidly and winds kick, but lack of deep cold thanks to lack of strong anticyclone means no rapid surge of cold for all of NewEng, though low level cold will be intense enuf in Nrn NewEng to turn ptype to snow and snow may come down hard in Nrn ME during this period as wraparound comma head will come all the way under belly of circulation...biggest question here is whether it misses just north of ME or delivers a windswept snow to Nrn Aroostook County, which is possible on Sun.  Farther southwest, upslope flow will be maximized in mountains of ME on Sun, but lots of instability Cu will layer the skies of NewEng with snow showers in most of the mountainous terrain.  As the upper low churns over Ern Canada, it essentially creates its own pool of cold air courtesy of dynamic cooling, and this cool pool settles over NewEng middle to end of next week, and though it is progged to be at least 8 C anomalously cold at 850, the shallow nature of the cold is likely to allow mixing and therefore modify the impact somewhat, though clearly below to much below normal temp regime will continue.

Matt

Tuesday Discussion:

1:10 PM:  No techie update yesterday thanks to server failure at provider - apologies, especially considering I'm off to a public appearance today so limited time to share my thoughts.  Let me get them out as quickly as possible:

Well defined vort max to swing southeast across VT/NH/ME overnight and into early Wed AM.  The cyclonic vorticity advection (CVA) ahead of this vort is fairly well distributed - largely normal to the flow - and that will provide extra impetus to generate convective precip overnight.  Couple this with cold air aloft providing instability and upslope flow in Nrn mountains and you have a fairly favorable setup for accumulating snow even though sfc winds may not be the ideal NW direction I'd like to see.  Nonetheless, 925 mb temps fall steadily late this afternoon thru Tue Ngt and this shud ensure elevated areas are cold enuf for snow.  To take thermal fcst profiles literally, no snow will fall below 1500 feet, but I'd expect the convective nature of the precip in the CVA ahead of the vort max to overcome this inhibiting factor and lower the snow level considerably.  Elevated terrain will benefit from the combo of cold profile, abundant moisture, good snow crystal growth and upslope flow to crank out amounts as high as 6"-8" in favored locales like Jay Peak and perhaps Sugarloaf, as well.  Enuf warm air in the valleys that locales below 500-600 feet will probably have trouble getting snow to stick well as sfc temps stay above freezing.  Still, vort max passage doesn't occur until Wed AM in Srn NH and near coastal plain of ME where some snowflakes certainly may mix in, and wouldn't want this to be a shock to the awakening public in the AM so have adlibbed this possibility accordingly.  Have carried D-1" rather far south, as well, but am stressing elevation dependence - bottom line here is that I'm untrusting of the pattern with the combo of instability and vorticity, I'm untrusting of the low-level wind flow that is not only non-ideal upslope north, but more importantly to this point is non-ideal downslope south, and I'm untrusting of moist low levels.  Nonetheless, anything that does survive the trip would die or ship out quickly Wed as a final mix of mostly raindrops and some snowflakes, tho upslope flow will strengthen on Wed in the Nrn mountains where snow showers will continue.  Let's also not forget the connection from Lake Ontario, which has dropped light rain showers in SW CT earlier today and tho it has broken up with diurnal htg and assoc mixing, should redevelop overnight tho will be warm enuf for rain in these areas.

Moisture mixes out a bit better on Wed but cold pool is slow to decay and while I expect more sunshine, more mixing, greater wind speeds than Tue, clouds will still bubble aplenty during the afternoon beneath the cool pool.  Thu is a decent break in the action, and the trend has been for slower progression of Fri system which makes sense for at least a little while as Pacific energy and Tropical Storm Paul merge in the trof over the SE US.  This significant amplification will slow the progression, but once Paul's remnants are absorbed into the circulation, this will enhance the thrust of warm and moist advection ahead of the storm, and precip should develop later Fri from SW to NE.  1020 mb bubble of high pressure over Ern Canada bridges to high pressure over MidAtl while col (area of light wind) sets up between these two anticyclones and the cyclones to the southwest and northeast of NewEng.  At Cornell University, one of my meteorology professors, Dr. Colucci always would say "always beware the col".  As the low level flow becomes weakly convergent in this coll, it serves as a magnet for secondary storm development and/or track, and the GFS is close to this line of thinking.  A track from the MidAtl coast to the col for a secondary low would allow cool air to hold into Nrn NewEng enuf for a significant accumulating snow event Fri Ngt into Sat and am carrying that in fcst for now, with liquid much more likely ptype in Srn NewEng.

Enjoy your day.

Matt


PERIODS OF SNOW TO RETURN TO NORTHERN NEW ENGLAND...SOUTHERN NEW ENGLAND CHILL ROLLS ON...HURRICANE PAUL EVENTUALLY A PLAYER IN OUR WEATHER

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

General Weather Summary:

An active weather pattern will continue for the next several days into the weekend, and will bring another strong storm by Friday night.  In the meantime, a large storm in the upper levels continues to churn over New England and will pivot a new spoke of energy over the six-state region Tuesday night.

In the meantime, a steady northwest wind has kept cool air in place across the region with plenty of clouds helping to ensure temperatures will have to struggle just to break the 50 degree mark in a lot of communities Tuesday afternoon.  These clouds come as a result of cold air aloft - often found with an upper level storm - and the difference between those very cold temperatures and the relatively warmer temperatures near the ground.  This, combined with moisture in the lower few thousand feet of the atmosphere, allows the clouds to continue bubbling up over New England through Tuesday.  While Southern New England is somewhat removed from the core of cold air aloft and will find only a few clouds growing tall enough to drop a sprinkle or shower Tuesday afternoon, Northern New England lay under the belly of the high-altitude storm, and that's where clouds will continue to grow tall enough to deposit pockets of rain and snow to the North Country, with some bursts rather heavy in intermittent spells.

With the approach of the next spoke of energy rotating around the storm, bands of rain and snow showers have already developed over Southern Quebec and have been rotating southward toward Northern New England, with scattered showers of rain and snow developing in the Northern Mountains ahead of the more organized activity.  Overnight Tuesday night, that organized precipitation will enter New England, falling as snow showers and heavier squalls in the higher terrain.  The Tuesday night snow will be somewhat of an elevation dependent snow, with areas below 1000 feet needing to see a heavy burst of snow to get much accumulation.  Nonetheless, I've carried the chance for a dusting as far south as Manchester, NH, for a push of rain and snow showers that will move through in the pre-dawn hours of Wednesday, moving south out of the mountains.  While the actual cities of Concord and Manchester may not see more than a few flakes mixed in, higher terrain around those areas may see enough to coat roadways in the early morning hours, and that will result in a few slick spots.  Farther north, overnight snows will accumulate into Wednesday morning, with as much as 6"-8" possible around Jay Peak, and several inches possible in the higher terrain of the Northern White Mountains and Mountains of Northwest Maine as well, especially above 1500 feet.

Sfx_accums_1

Though snow showers will start the day in some spots Wednesday morning, the passage of the upper level disturbance and an associated wind shift at the surface will bring increased wind gusts, continued chilly air, but mostly dry conditions to most of New England.  Though some snow showers and heavier squalls may linger for a time in the mountains, the remainder of New England should find more sunshine than was seen on Tuesday, though the effect on the daily high temperature will be minimal.  After a chilly night Wednesday night with winds subsiding, Thursday will bring sunshine and moderating temperatures - a break in the action before our weather turns stormy once again.

This end-of-week storm comes with a history, as two key weather systems will come together in its formation.  The first is Hurricane Paul, heading for Baja and packing winds of 80 mph as of this writing, but forecasted to weaken before making landfall.  Nonetheless, Paul still will represent a large mass of moisture, heat and energy as he crosses Texas en route to the southeastern United States, carried by the subtropical jet stream.  To the north, a strong energetic disturbance is moving southeast down the Western Canada coastline, caught in the polar jet stream that carries energy centers and cold air from the north.  This storm, too, will dive toward the Southeastern U.S., where it will meet with the remnants of Paul late in the week.  The result will be a strengthening storm to the southwest of New England on Thursday, and this storm will launch a slug of meaningful warmth and moisture toward New England on Friday.  With cool air in place already, and clouds on the increase, temperatures will remain cool.  Additionally, a new fair weather cell packed with cool Canadian air will be settling into Southern Canada during the period, and this will provide a supply of cold air to New England.  The result will be a stubborness of the cold air to let go from Northern New England as moisture comes streaming in, and this likely will crank out snow across Northern New England when precipitation moves into New England later Friday or Friday night into Saturday, and if all works out as it currently appears, plowable snow would occur on a more widespread scale than the past day or two have brought.   Farther south, it's more likely that air will be warm enough for liquid to fall Friday night into Saturday.

Sfx_matt_jet1 Sfx_matt_jet2_1 Sfx_matt_jet3

For most areas, Saturday showers of rain and snow would taper and give way to gradual clearing, though clouds may linger across the north.  It's worth noting that - contrary to what we see in most storms - this storm would be unlikely to deliver a shot of hearty cold air behind it, and actually would likely bring warmer days after its passage, given its tropical origins and absence of cold air behind the storm circulation.

Have a great Tuesday.

Matt

Matt's Technical Meteorological Discussion:  Updated Tuesday, October 24 at 1:10 PM

No techie update yesterday thanks to server failure at provider - apologies, especially considering I'm off to a public appearance today so limited time to share my thoughts.  Let me get them out as quickly as possible:

Well defined vort max to swing southeast across VT/NH/ME overnight and into early Wed AM.  The cyclonic vorticity advection (CVA) ahead of this vort is fairly well distributed - largely normal to the flow - and that will provide extra impetus to generate convective precip overnight.  Couple this with cold air aloft providing instability and upslope flow in Nrn mountains and you have a fairly favorable setup for accumulating snow even though sfc winds may not be the ideal NW direction I'd like to see.  Nonetheless, 925 mb temps fall steadily late this afternoon thru Tue Ngt and this shud ensure elevated areas are cold enuf for snow.  To take thermal fcst profiles literally, no snow will fall below 1500 feet, but I'd expect the convective nature of the precip in the CVA ahead of the vort max to overcome this inhibiting factor and lower the snow level considerably.  Elevated terrain will benefit from the combo of cold profile, abundant moisture, good snow crystal growth and upslope flow to crank out amounts as high as 6"-8" in favored locales like Jay Peak and perhaps Sugarloaf, as well.  Enuf warm air in the valleys that locales below 500-600 feet will probably have trouble getting snow to stick well as sfc temps stay above freezing.  Still, vort max passage doesn't occur until Wed AM in Srn NH and near coastal plain of ME where some snowflakes certainly may mix in, and wouldn't want this to be a shock to the awakening public in the AM so have adlibbed this possibility accordingly.  Have carried D-1" rather far south, as well, but am stressing elevation dependence - bottom line here is that I'm untrusting of the pattern with the combo of instability and vorticity, I'm untrusting of the low-level wind flow that is not only non-ideal upslope north, but more importantly to this point is non-ideal downslope south, and I'm untrusting of moist low levels.  Nonetheless, anything that does survive the trip would die or ship out quickly Wed as a final mix of mostly raindrops and some snowflakes, tho upslope flow will strengthen on Wed in the Nrn mountains where snow showers will continue.  Let's also not forget the connection from Lake Ontario, which has dropped light rain showers in SW CT earlier today and tho it has broken up with diurnal htg and assoc mixing, should redevelop overnight tho will be warm enuf for rain in these areas.

Moisture mixes out a bit better on Wed but cold pool is slow to decay and while I expect more sunshine, more mixing, greater wind speeds than Tue, clouds will still bubble aplenty during the afternoon beneath the cool pool.  Thu is a decent break in the action, and the trend has been for slower progression of Fri system which makes sense for at least a little while as Pacific energy and Tropical Storm Paul merge in the trof over the SE US.  This significant amplification will slow the progression, but once Paul's remnants are absorbed into the circulation, this will enhance the thrust of warm and moist advection ahead of the storm, and precip should develop later Fri from SW to NE.  1020 mb bubble of high pressure over Ern Canada bridges to high pressure over MidAtl while col (area of light wind) sets up between these two anticyclones and the cyclones to the southwest and northeast of NewEng.  At Cornell University, one of my meteorology professors, Dr. Colucci always would say "always beware the col".  As the low level flow becomes weakly convergent in this coll, it serves as a magnet for secondary storm development and/or track, and the GFS is close to this line of thinking.  A track from the MidAtl coast to the col for a secondary low would allow cool air to hold into Nrn NewEng enuf for a significant accumulating snow event Fri Ngt into Sat and am carrying that in fcst for now, with liquid much more likely ptype in Srn NewEng.

Enjoy your day.

Matt


BURSTS OF HEAVY SNOW WILL CONTINUE IN THE NORTHERN MOUNTAINS...DEEP CHILL MOVING SOUTH

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

General Weather Summary:

Two storms are interacting on either side of New England on Monday - one to our north across Southern Quebec, and the other across the waters southeast of New England.  These two storms are connected by a weak front, which marks a shift in wind and also has been helping to focus moisture into rainfall and snowfall for parts of New England.  At last check, Sunday River ski resort reports 7.5" of NEW SNOW today on Jordan Bowl at 1800 feet in elevation, 2" that fell at the base in a burst of heavier rainfall that turned to snow in a process known as "dynamic cooling" - when rapidly rising air is cooled quickly.  Similar reports of snow have been coming back from across the North in heavier bursts of precipitation.  Check out the pics!

Sunday River:  Sfx_sky1 Sfx_sky2

Sugarloaf:  Sfx_sky3 Sfx_sky4

Dick Sharron's House in Glen, NH, reporting for www.northconwayweather.comSfx_sky5 Sfx_sky6

Otherwise, a rainy pre-dawn Monday in many areas gave way to drying conditions and breaks of sunshine through the day in Southern New England as winds shifted to the west and northwest, ushering in cooler but drier air, further drying as it slopes down the hills and mountains of New England.  The "occluded" front laid across New England between a Canadian storm and an ocean storm will continue to focus moisture as rainfall across the State of Maine through the day on Monday, with showers lingering in Northern New Hampshire and Vermont, though in most areas, temperatures will remain mild enough for all raindrops.  In a few elevations above 1000 feet, morning rain ended as a brief burst of snow in the White Mountains, and this will be the case in the higher terrain of the Maine Mountains, where snow will mix in during heavier bursts of precipitation.  All the while, the aforementioned front will be gradually pivoting northeast across Maine, shifting winds from the west and northwest behind it, gradually filtering colder air into New England from Canada.  This cooler air, combined with an upper level storm providing spiraling bundles of energy aloft, will generate snow showers in the mountains of Northern New England Monday night, and while the wind direction in the lowest few thousand feet of the atmosphere won't be perfect for significant accumulating snow, we should see at least a few inches in some of the higher terrain.  Elsewhere in New England, expect lots of clouds through the day Monday thanks to plenty of lingering moisture in the lower few thousand feet of the atmosphere and cold air spilling in aloft, though breaks of sun will emerge between the clouds.  Monday night will bring a partly cloudy and cool night with a persistent brisk northwest wind adding a bite to an already chilly airmass.

Expected Snowfall Accumulations - Please note, this is AVERAGE for lower elevations, and amounts will continue to be higher above 1500 feet:  Sfx_accums

Tuesday and Wednesday will be two rather similar days.  That is, a chilly west and northwest flow of air will continue at the surface, locking cool Canadian air in place, while offsetting sunshine will be difficult to find in abundance given the stalled upper level storm over New England providing a cold pool of air aloft.  The difference in temperature between this very cold air thousands of feet above our heads, and warmer air near the surface, will continue to generate many puffy cumulus clouds, some of which will drop a few showers of rain in Southern New England, and a few showers of snow and rain with heavier bursts of snow across the mountains of the North.  In the localized, heavier bursts of snow beneath spokes of energy under the large storm aloft, quick accumulations of snow in a short period of time may make some mountain roads slippery Tuesday and Wednesday afternoon.

Expect a slow moderation of the airmass on Thursday with a bit more sunshine and a break between storms before yet another moderately intense storm approaches for Friday.  It's possible that this end-of-week storm falls as a wintry mix for Northern New England with rain showers farther south, but the effects of the storm will be watched closely as it will leave cool air in its wake to begin the weekend.  The problem (dependent upon perspective) here is that the weather pattern will be quite progressive, or fast moving, and that will mean the next disturbance won't be far behind this shot of cold air, which may leave enough cold air in place for a more widespread wintry mix with the next disturbance this weekend!

I'll keep you posted, for sure.

Technical Discussion:  Technical problems with the server (out of my control) have kept me from updating today.  My apologies to those of you checking back for it today!

Matt


STRONG STORM CROSSES NEW ENGLAND FRIDAY...BRISK WEEKEND...THEN ANOTHER STRONG STORM TO LEAD US INTO COLD WEEK

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

General Weather Summary:

Lots going on behind the scenes besides just the storm, so late on the update - my apologies.

A major storm will cross New England today, to be remembered largely for the wind it will generate on the trip through.  This storm will be the first in a series over the next couple of weeks, but more specifically, the first in a set of two storms that will usher in a new, cold weather pattern for next week.

Pertinent Maps (more below in discussion):

Intro_graphic1 Intro_graphic2 Intro_graphic3

In the meantime, relatively warm air delivered a mild start to most of New England Friday morning.  The advance of more warmth and moisture to New England - the result of a deep tropical moisture tap - brought one round of rain through most of the six-state region overnight Thursday night into Friday morning, while rains continued to fall on the warm side of a cool front settling toward Northern New England from Southern Canada.  With a very strong impulse of moisture-loaded energy set to march over New England later Friday, periods of rain, heavy at times, will continue to migrate from southwest to northeast across the region.  Though there will be breaks in the rain at times, the combination of strong energy, ample moisture, and the resultant surface storm will ensure rain fills in for most areas Friday afternoon, with the heaviest amounts falling where steady rains have been falling for quite some time - in Northern and Western New England - and it's in these areas where localized flooding of streams is possible, while we all may see localized flooding of streets in heavier downpours.

Additionally, the passage of the surface storm will bring a quickly falling barometric pressure - a sure sign of storminess - and this will help to transport more warmth and moisture into Southern New England...enough for thunderstorms to develop Friday afternoon and some of the storms will have the potential to tap strong winds aloft and cause locally damaging wind gusts.  As the storm center moves through Eastern New England, barometric pressures will rise rapidly behind it as winds shift to the west, and this pressurized air will create widespread wind gusts to 60 mph Friday evening through the overnight.  These winds will have the capability of bringing down trees, tree limbs and power lines through the overnight, and will help to make temperatures in the 30s feel like the 20s by dawn.  Additionally, keep in mind that signs, banners, and lightweight objects like Halloween decorations will blow around in the overnight into Saturday.  Finally, these winds will be transporting colder air into New England, and rain will turn to snow before ending in the mountains of Vermont, New Hampshire and extreme Northwestern Maine, where a dusting of snow will fall, with amounts to two inches in higher terrain.  Sfx_ptype Sfx_wind_fcst_00000

The drier and cool air moving in will bring a decent Saturday after any lingering snow showers in Northeastern Maine, with a blend of sun and clouds elsewhere, but winds will continue to be quite active, with a west-northwest wind gusting to 40 mph!  This will make the coxswain's jobs (those who steer the boats) very challenging for the Head of the Charles, and will continue to mean signs and banners serve as sails in the winds, along with tents, so please be sure everything is well-secured.  After a chilly Saturday night, expect dry conditions to begin Sunday - so...all in all...most of New England does enjoy a decent fall weekend.  That said, the next blast of energy - two strong disturbances merging from the Pacific and from near the North Pole - will be gathering strength and moisture across the nation's midsection.  Clouds will increase Sunday and showers will likely develop by evening from west to east.  This will set the stage for what will likely be a powerful storm for New England Monday into Tuesday.  With cold air prior to the storm, and more cold air on the backside of the circulation, the threat for more widespread snow is present across Northern New England at the beginning of next week.  This is a potential that needs to be monitored carefully for a possible early-season snow on especially the Northern Mountains.  The most likely scenario would be for precipitation to begin late Sunday as a mixture of rain and snow or perhaps all snow but light in intensity across Northern Maine later Sunday night.  For a time, most areas will see rain on Monday, but with substantially colder air available immediately west and north of the storm, rain should transition to snow later Monday or Monday night across the North Country.  With moisture present, a northwest wind pushing up against the mountain faces, and cold air streaming in, "upslope" snows are likely to be generated Monday night through Tuesday in the Greens, parts of the Whites and the mountains of Maine.

Sfx_matt_jet1_00000 Sfx_matt_jet2 While this surge of cold air will bring the potential for an early-season accumulating snow to Northern New England early next week, we'll all feel the result, as next week should be marked by much-below normal temperatures - perhaps producing record cold around midweek from the Northeast to the Mid-Atlantic, though admitedly, our records are already quite cold for the middle of next week - some dating back to the late 1800's, and the Mid-Atlantic may see a better chance of realizing record values.  None the less, it'll be plenty cold!

Have a wonderful weekend.

Matt

Matt's Technical Meteorological Discussion:  Updated Friday, October 20 at 2:30 PM

Wind gust to 61 mph recorded at KMPO in Ern PA at 1739Z with line of low topped convection moving E that will be in Wrn Srn NewEng at 1530 EDT and will reach KBOS between 1800 and 1900 EDT with damaging wind burst behind wind shift and possibly svr thunder along the line.  Warm sector has bled into Srn NewEng according to sfc pressure/theta-e composite and deepening storm has reached 993 mb already before even reaching Hudson Valley.  Will continue strengthening as it moves over Srn NewEng with 4-5 mb pressure rise/fall couplet and strong isallobaric component to the wind.

Winds may die down for a couple of hours behind front after the big gusts as cold and dry advection is slightly delayed, but once CAA commences, winds will gust once again up to 60 mph and become more widespread with damage done thru the overnight, scattered power outages, trees down, lightweight objects blown around.  Please stress importance in forecasts of securing objects like signs and banners that can act as sails.  Area of heaviest rain to move E ahead of potent vort max and in area of greatest isentropic lift in WAA across Wrn/Nrn NewEng where flooding of streams and streets most likely.  Snow reported in KELZ and KBFD earlier today in Srn NY/Nrn PA - both are elevated stations but KELZ lowered to 1/2 mile in SN and this is a sign of the dynamic and advective cooling that will take hold in Nrn NewEng this eve and tonight.  If we could snow during diurnal max there...and just flipped from rain to snow at diurnal max in KART (Watertown, NY)...we will have no problem doing the same in elevated locales of VT/NH as soon as 00Z/03Z respectively.  Most areas shouldn't see more than a half inch or so up the spine of the Greens, but higher terrain will see a couple of inches, esp near 1800 feet in elevation.

Likely lingering snow showers early Sat in NW ME - tho perhaps still too mild in wraparound warmth aloft for NE ME - but most of NewEng transitions to windy sun/cloud blend.  Downsloping component present in Ern areas and dry enuf air to preclude upslope development in Wrn/Nrn areas, but winds should still gust to 40 mph first half of day with 850 winds still cranking.

As winds taper Sat Ngt, temps tumble.  Tds in lower 30s put lows near the same, tho some breeze still present will prevent widespread decoupling.  Sunday brings moderation and less wind but next shortwave already increasing clouds thru the day.  Am still holding showers off until eve but model runs holding it off until night are too slow given vorticity advection quickly moving E.  A dynamic situation again for Mon/Tue and I continue to hedge on the colder and stormier side of the solutions.  With deepening upper low forecasted to shift directly overhead, we won't see worst case scenario of deep phasing, but still plenty of energy and thermodynamics at work.  First, slug of warm and moist advection ahead of upper low will crank out rain Sun Ngt into early Mon for most of NewEng as upper low shifts SE from Hudson Bay to Lake Superior.  For a lot of NewEng this is probably it and it's done early Mon with some clearing late and winds kicking up.  This will not be the case in the North Country, however, where the upper low will catch the surface system as it tries to ride out north and east, and effectively stall it.  The result is going to be low level cold advection, moisture wrapping around the low in the midlvls and dynamic cooling as the upper low shifts east, and this should result in significant bursts of convective snow in Nrn NewEng - esp the mountains of ME - on Mon, and esp later in the day.  Then we have ample moisture to interact with upslope NW flow and CAA to setup accumulating upslope snows in Nrn VT, Nrn NH and NW ME Mon Ngt thru Tue.  By Tue, I expect cold enuf air to keep Srn NewEng in 40s, Nrn NewEng in 30s.  As for records, min temps are quite cold Tue and Wed, and with an active wind that will be difficult to challenge, but record low maximum temps are possible Tue or Wed.  Records more likely to fall in the Mid-Atl.

That's all for today - enjoy the weekend.

Matt

Wednesday's Discussion:

3:05 PM:  'Tis the season for surges of winter amidst lingering tropical warmth and moisture, and NewEng shud see both in the coming week.  Tropical airmass in place as of this writing thanks to delivery by former TS Norman who chugged over NewEng last night dropping rainfall amounts over an inch to some, and under a quarter inch to others.  Nonetheless, the storm has left behind an appreciable chunk of tropical warmth directly from the Gulf of Mexico and areas with sun have seen corresponding quick temp rises.

Shortwave embedded in the flow to cross between 18Z and 00Z this afternoon and have adlibbed isolated shra/tsra with warmth and low level moisture in Srn NewEng, tho cov'g should be limited.  Enuf dry air aloft for breaks to remain in clouds overnight tho fog will be dense in many areas with relatively light wind and high dewpoints.

Fog and sun starts Thu before clouds advance along midlvl baroclinic zone stretched across Nrn NewEng.  Approach of shortwave energy to interact with this zone in generation of showers for Nrn NewEng by early afternoon, expanding S as cool front approaches from NW and baroclinic zone tightens.  Leading s/w ejects NE from base of Central US trof on Thu and fills showers and period of rain in across Srn NewEng Thu eve into the ngt.  Thereafter, attention turns to strong shortwave migrating rapidly E in Westerlies.  Tho this s/w will be strong, it will also be progressive until it reaches NE NewEng later Fri, where it interacts with colder air aloft and deepens/closes off NE of ME.  There has been some issue as to the path of assoc sfc low pressure center(s) with this vort max, more so with the secondary low than the primary, which will cut north of NewEng.  The secondary has been progged from NYS to offshore NewEng as a nor'easter (ECMWF) but consensus likely to be best, not to mention the solution of the GFS Ensemble mean - which places triple point low over Ern NewEng - inland - perhaps getting Cape Cod into warm air as it swings thru but bringing gale SE gusts to the mid and downeast ME coast and perhaps gale force SW gusts under the belly of the strengthening sfc low to SE NewEng.

As this storm wraps up while moving NE Fri Ngt into Sat, still feel there is enuf basis to include potential of snow in the fcst for Nrn/NE ME with wraparound precip early Sat.  While operational models have varied greatly for this time period, GFS Ensemble mean has stuck to its guns of keeping high chc pops in NE ME at the same time cold air in Srn Canada is ingested into storm center.  Additionally, with upper level low closing off, moisture wraps around back of circulation and will maintain chc snow showers in Nrn ME for Sat AM.  Precip also may end as a few flakes in Nrn mountains of NE VT/NH where upslope flow can generate enuf lift, but dry air quickly moving in behind storm by that point.  Ridging is quick to move back in aloft and this will mean cool but dry most of NewEng Sat into Sun.  Next s/w in line is one that recently ejected from the Aleutian low and will drop into Central US trof, ejecting NE into NewEng like its predecessor, but with enuf airmass modification for rain in all locales except perhaps in Nrn ME where warm and moist advection will ride overhead before llvl flow can swing out of the N and this means a brief pd of light WAA snow would be possible in Nrn ME later Sun ahead of the s/w.  Warm advection should win out Sun Ngt, however, with all areas going to liquid.

The real meteorological fun only grows more intense early next week, as a strong shortwave dropping south from the polar vortex near the North Pole will merge with a Pacific counterpart and amplify handily at the base of the trof to our west on Monday.  The trick here is that the storm Sun into Mon will have already yanked down a hearty chunk of cold air from Canada, and the motherload of cold will be heading east across the Midwest.  This will be another chunk of record cold in Iowa, and will end up spelling record cold for the Mid-Atlantic and at least some of the Northeast by the middle of next week.  But the transition to this cold will likely come with an intense cyclone as the upper low deepens and generates its own cold air through continued dynamic cooling over Southeastern Canada, and drives sfc cyclone development over or very near to NewEng on Monday.  This storm will already have picked up plenty of Gulf moisture during its amplification, and with the cold air to the north and west of the storm, sufficient baroclinicity will meet sufficient vorticity to generate a powerful storm whose circulation will tap the cold to our west and northwest.  The result should be enuf cold air meeting up with a wound up storm that will wrap significant mositure around its west side to generate snows from Nrn ME thru the North Country where upslope flow will play a significant role.  In fact, the situation looks quite favorable for accumulating upslope flow snows in esp the Green Mountains as cold advection meets with moisture on a strong NW flow.  While this will not spell snow for Srn NewEng, it will spell a great pattern for cold air - a prolonged NW flow at the sfc meeting up with an airmass to the tune of 12 C below normal, creating record low temperatures, especially by midweek when winds will weaken but WAA will not have begun yet, and overnight lows should plummet.

What could change this outlook?  Obviously storm track and timing of cyclogenesis is crucial.  Slightly farther east...or west...upsets how the cold air and the storm can interact and the wind direction.  This won't change the cold - that's coming - what it would effect is the potential for accumulating snow.  But at this point, I'd say it's certainly the best chance of snow the North Country has had since spring.

We'll keep an eye on it together.

Matt

Monday's Discussion:

1:40 PM:  Slow moving wx pattern has been northern stream dominated of late but that will change in the coming days as trof continues to dig in Wrn US and sends subtropical jet springing northward.  This subtropical jet is active with the remnant of Norman, a former tropical storm who churned across the Eastern Pacific before crossing Mexico, then regaining an impressive satellite signature over the Western Gulf of Mexico this weekend before making landfall early Monday into the Eastern TX coastline, where winds gusted in excess of 40 mph.  Torrential rain has been lifting north and will turn NE as it encounters the fast flow of the westerlies across the Midwest, and the vort max assoc with the remnant of Norman will charge NE and directly over Srn NewEng late Tue Ngt and Wed AM, bringing a shot of heavy rain with it.

In the meantime, high altitude Ci clouds will spill overhead in waves Mon Ngt as thicker moisture puts on the brakes crossing OH Valley, but dry air and light wind shud still allow for temps to fall quickly after sundown.  If enuf Ci spill overhead, my fcstd low temps will be a bit too warm, tho with Tds in the upper 20s to around 30, I'd imagine most locales will see frost, and concern is for perhaps pockets of black ice where freezing fog may result in Pioneer Valley through Monadnock Region and Central NH.  Any sun early Tue will quickly help to mix the atmosphere, tho Ci clouds will thicken and lower as midlvl moisture spreads NE across NewEng thru Tue.

Slug of moisture slated for Tue Ngt shud come in with progged vort max as referred to in first paragraph.  12Z GFS a bit drier than its preceding run, 12Z NAM not much more moist and still noticeably drier than GFS.  Canadian Ensembles and GFS Ensembles both lean toward wetter solution, while most guidance insists on quick solution.  Wet and quick both make the most sense with slug of isentropic lift intense thanks to tropical slug but quick moving embedded in the subtropical jet.  The net result shud be a shot of 1" QPF for most of Srn NewEng with locally higher amounts, then lesser amounts Nrn half of NewEng.  As warm and moist advection wanes Wed AM, rain will taper, tho quick progression of warmth and moisture aloft leaves behind the corridor of warm advection in the llvls, and this means plenty of moisture is left behind at 850 mb and below.  Hence, clouds linger thru most of day Wed tho a few breaks not impossible Wrn areas as sfc inverted trof/weak warm front moves E and brings westerly flow, while drizzle immediately behind rain assoc with shift of winds to the N and llvl cool advection shud be found in ME coastline.

Still will have sfc low assoc with llvl remnant of Norman that will eject off MidAtl coastline and pass SE of NewEng, while new shortwave induces sfc low development in the Great Lakes and drags cold front with multiple waves across OH and TN valley.  This front with waves will enter the I-95 corridor Thu Ngt and strengthening wave with tropical moisture will be rippling thru MidAtl Thu Ngt en route to NewEng for Fri.  This happens at the same time Nrn stream wave moves E, carrying cool air behind it, and this is enuf to at least peak interest in how the incoming cold air will interact with northward rippling moisture-loaded wave.  I say this because, at some point, these two features really should link up, but the question is how quickly does that happen?  The 12Z GFS is one of the quickest to merge, and while I do think the GFS tends to handle waves of fronts better than most of the guidance, the key here is more in the handling of the Nrn stream shortwave, which takes on a neutral/negative tilt at the end of this week but does so just a bit too far west on Thu to let the cold come flooding in as quickly as the new GFS would paint.  I think the end result is that the merger of cold and tropical occurs E of ME later Fri, and this means Nrn ME will be on-guard for wrap-around precip...and yes, perhaps snow...late Fri into early Sat.  Certainly something to watch carefully.

Another watcher will be the beginning of next week, which the GFS Operational has not been nearly as bullish on as its Ensemble member counterparts, but bullish may be the way to go for next Mon/Tue as polar vortex deepens over SCentral Canada before nudging east and quite literally helps to create its own cold air that should be quite eager to move into NewEng, with strong energy aloft and sfc baroclinicity ready to encourage sfc low development over or near Ern NewEng, and once again raising eyebrows for those interested in snow prospects for the North.

We'll see...plenty to work out between now and then.

Matt


SERIES OF STRONG STORMS TO LEAD NEW ENGLAND INTO MUCH COLDER PATTERN

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

General Weather Summary:

While New England enjoys a relatively mild day on Thursday, big changes are on the way, as a storm Friday will mark the start of a transition in the weather pattern to a decidedly more winter-like appearance by next week.  Intense energy dropping south from the North Pole will deepen both the cold air and increase the potential for storm growth in the Eastern United States by the beginning of next week.

Thursday undoubtedly began with more clouds than I'd anticipated - thanks at first to low level moisture trapped after yesterday's rains that bubbled into clouds during the overnight - clouds that I expected to be near ground level as fog, but instead formed above our heads.  These clouds developed beneath what's called and "inversion" in the world of meteorology.  Normally, temperatures get colder the higher up one goes in the sky in the layer of atmosphere where weather is made, but an inversion is a warm layer of air aloft - that is, a setup where the air gets warmer as one rises in altitude, and that was the case early Thursday morning.  With a weakening sun angle, and cool air trapped beneath a consistently warming atmosphere aloft, it becomes difficult to entirely erode this inversion, and the result is stubborn clouds.  Nonetheless, downsloping flow allowed for some mixing in the Connecticut River Valley Thursday morning, and that area of drier air has slowly been moving east across New England, followed in turn by more clouds that you can follow with the visible satellite imagery linked at left (during the day - infrared imagery after dark).  With breaks of sun amidst the clouds, temperatures will once again respond fairly well, especially when aided by a southwest breeze.

Meanwhile, the next round of clouds is already on the move toward New England, well ahead of the next developing storm over the Mississippi River Valley, where lines of showers and intense thunderstorms are raging Thursday.  This developing storm is the result of one chunk of substantial energy carving out a trough in the jet stream over the Central United States.  Remember that the jet stream is the fast river of air aloft that steers our storm systems and acts as a thermostat for the atmosphere, separating cold air to the north from warmer air to the south.  With a storm developing at the dip in these jet stream winds - the trough over the Mississippi Valley - it will be able to feed off of the difference between warmth and cool air, and will be driven by the strong, energetic jet stream winds aloft toward New England.  As clouds thicken from north to south during the day Thursday, showers will follow suit, with showers developing Thursday afternoon in the north, then expanding over Central New England during the evening.  By Thursday night, showers will expand into Southern New England witih most areas seeing showers by midnight.

All the while, the developing storm to our southwest will be strengthening and charging toward New England.  This should deliver a swath of rain, heavy at times, to New England on Friday, with gusty winds as the storm strengthens directly overhead.  I continue to favor a track over Eastern New England on Friday, and this will likely dump heavy rains in most of New England, falling fastest between mid-morning and late afternoon.  This will limit warm winds to areas east of the storm track - especially Cape Cod and the Islands - where thunder would be possible in some of the rain bands.  Additionally, this track will bring a strengthening storm over Eastern New England, cranking winds up quickly enough for gale force gusts from the southeast ahead of the storm in the Mid and Downeast coasts of Maine late Friday afternoon and Friday evening, and perhaps strengthening the storm quickly enough to even deliver gale force winds from the southwest to Cape Cod and adjacent waters Friday evening under the belly of the storm.  All the while, the counter-clockwise circulation will continue to tap cold air from Southern Canada, tugging it closer to New England, and is likely to create a period of snow showers for the mountains of Vermont, New Hampshire and Maine Friday night (into Saturday morning in northeastern Maine) before tapering as drier air takes hold of New England.

The drier and cool air moving in will bring a decent Saturday after any lingering snow showers in Northeastern Maine, with a blend of sun and clouds elsewhere.  After a chilly Saturday night, expect dry conditions to begin Sunday - so...all in all...most of New England does enjoy a decent fall weekend.  That said, the next blast of energy - two strong disturbances merging from the Pacific and from near the North Pole - will be gathering strength and moisture across the nation's midsection.  Clouds will increase Sunday and showers will likely develop by evening from west to east.  This will set the stage for what will likely be a powerful storm for New England Monday into Tuesday.  With cold air prior to the storm, and more cold air on the backside of the circulation, the threat for more widespread snow is present across Northern New England at the beginning of next week.  This is a potential that needs to be monitored carefully for a possible early-season snow on especially the Northern Mountains.  The most likely scenario would be for precipitation to begin late Sunday as a mixture of rain and snow or perhaps all snow but light in intensity across Northern Maine later Sunday night.  For a time, most areas will see rain on Monday, but with substantially colder air available immediately west and north of the storm, rain should transition to snow later Monday or Monday night across the North Country.  With moisture present, a northwest wind pushing up against the mountain faces, and cold air streaming in, "upslope" snows are likely to be generated Monday night through Tuesday in the Greens, parts of the Whites and the mountains of Maine.

Sfx_matt_jet1_00000 Sfx_matt_jet2 While this surge of cold air will bring the potential for an early-season accumulating snow to Northern New England early next week, we'll all feel the result, as next week should be marked by much-below normal temperatures - perhaps producing record cold around midweek from the Northeast to the Mid-Atlantic, though admitedly, our records are already quite cold for the middle of next week - some dating back to the late 1800's, and the Mid-Atlantic may see a better chance of realizing record values.  None the less, it'll be plenty cold!

Have a wonderful Thursday.

Technical Discussion:  Another public appearance today will keep me from a techie discussion, but will have on tomorrow to take us into an exciting weekend.

Matt

Matt's Technical Meteorological Discussion:  Updated Wednesday, October 16 at 3:05 PM

'Tis the season for surges of winter amidst lingering tropical warmth and moisture, and NewEng shud see both in the coming week.  Tropical airmass in place as of this writing thanks to delivery by former TS Norman who chugged over NewEng last night dropping rainfall amounts over an inch to some, and under a quarter inch to others.  Nonetheless, the storm has left behind an appreciable chunk of tropical warmth directly from the Gulf of Mexico and areas with sun have seen corresponding quick temp rises.

Shortwave embedded in the flow to cross between 18Z and 00Z this afternoon and have adlibbed isolated shra/tsra with warmth and low level moisture in Srn NewEng, tho cov'g should be limited.  Enuf dry air aloft for breaks to remain in clouds overnight tho fog will be dense in many areas with relatively light wind and high dewpoints.

Fog and sun starts Thu before clouds advance along midlvl baroclinic zone stretched across Nrn NewEng.  Approach of shortwave energy to interact with this zone in generation of showers for Nrn NewEng by early afternoon, expanding S as cool front approaches from NW and baroclinic zone tightens.  Leading s/w ejects NE from base of Central US trof on Thu and fills showers and period of rain in across Srn NewEng Thu eve into the ngt.  Thereafter, attention turns to strong shortwave migrating rapidly E in Westerlies.  Tho this s/w will be strong, it will also be progressive until it reaches NE NewEng later Fri, where it interacts with colder air aloft and deepens/closes off NE of ME.  There has been some issue as to the path of assoc sfc low pressure center(s) with this vort max, more so with the secondary low than the primary, which will cut north of NewEng.  The secondary has been progged from NYS to offshore NewEng as a nor'easter (ECMWF) but consensus likely to be best, not to mention the solution of the GFS Ensemble mean - which places triple point low over Ern NewEng - inland - perhaps getting Cape Cod into warm air as it swings thru but bringing gale SE gusts to the mid and downeast ME coast and perhaps gale force SW gusts under the belly of the strengthening sfc low to SE NewEng.

As this storm wraps up while moving NE Fri Ngt into Sat, still feel there is enuf basis to include potential of snow in the fcst for Nrn/NE ME with wraparound precip early Sat.  While operational models have varied greatly for this time period, GFS Ensemble mean has stuck to its guns of keeping high chc pops in NE ME at the same time cold air in Srn Canada is ingested into storm center.  Additionally, with upper level low closing off, moisture wraps around back of circulation and will maintain chc snow showers in Nrn ME for Sat AM.  Precip also may end as a few flakes in Nrn mountains of NE VT/NH where upslope flow can generate enuf lift, but dry air quickly moving in behind storm by that point.  Ridging is quick to move back in aloft and this will mean cool but dry most of NewEng Sat into Sun.  Next s/w in line is one that recently ejected from the Aleutian low and will drop into Central US trof, ejecting NE into NewEng like its predecessor, but with enuf airmass modification for rain in all locales except perhaps in Nrn ME where warm and moist advection will ride overhead before llvl flow can swing out of the N and this means a brief pd of light WAA snow would be possible in Nrn ME later Sun ahead of the s/w.  Warm advection should win out Sun Ngt, however, with all areas going to liquid.

The real meteorological fun only grows more intense early next week, as a strong shortwave dropping south from the polar vortex near the North Pole will merge with a Pacific counterpart and amplify handily at the base of the trof to our west on Monday.  The trick here is that the storm Sun into Mon will have already yanked down a hearty chunk of cold air from Canada, and the motherload of cold will be heading east across the Midwest.  This will be another chunk of record cold in Iowa, and will end up spelling record cold for the Mid-Atlantic and at least some of the Northeast by the middle of next week.  But the transition to this cold will likely come with an intense cyclone as the upper low deepens and generates its own cold air through continued dynamic cooling over Southeastern Canada, and drives sfc cyclone development over or very near to NewEng on Monday.  This storm will already have picked up plenty of Gulf moisture during its amplification, and with the cold air to the north and west of the storm, sufficient baroclinicity will meet sufficient vorticity to generate a powerful storm whose circulation will tap the cold to our west and northwest.  The result should be enuf cold air meeting up with a wound up storm that will wrap significant mositure around its west side to generate snows from Nrn ME thru the North Country where upslope flow will play a significant role.  In fact, the situation looks quite favorable for accumulating upslope flow snows in esp the Green Mountains as cold advection meets with moisture on a strong NW flow.  While this will not spell snow for Srn NewEng, it will spell a great pattern for cold air - a prolonged NW flow at the sfc meeting up with an airmass to the tune of 12 C below normal, creating record low temperatures, especially by midweek when winds will weaken but WAA will not have begun yet, and overnight lows should plummet.

What could change this outlook?  Obviously storm track and timing of cyclogenesis is crucial.  Slightly farther east...or west...upsets how the cold air and the storm can interact and the wind direction.  This won't change the cold - that's coming - what it would effect is the potential for accumulating snow.  But at this point, I'd say it's certainly the best chance of snow the North Country has had since spring.

We'll keep an eye on it together.

Matt

Monday's Discussion:

1:40 PM:  Slow moving wx pattern has been northern stream dominated of late but that will change in the coming days as trof continues to dig in Wrn US and sends subtropical jet springing northward.  This subtropical jet is active with the remnant of Norman, a former tropical storm who churned across the Eastern Pacific before crossing Mexico, then regaining an impressive satellite signature over the Western Gulf of Mexico this weekend before making landfall early Monday into the Eastern TX coastline, where winds gusted in excess of 40 mph.  Torrential rain has been lifting north and will turn NE as it encounters the fast flow of the westerlies across the Midwest, and the vort max assoc with the remnant of Norman will charge NE and directly over Srn NewEng late Tue Ngt and Wed AM, bringing a shot of heavy rain with it.

In the meantime, high altitude Ci clouds will spill overhead in waves Mon Ngt as thicker moisture puts on the brakes crossing OH Valley, but dry air and light wind shud still allow for temps to fall quickly after sundown.  If enuf Ci spill overhead, my fcstd low temps will be a bit too warm, tho with Tds in the upper 20s to around 30, I'd imagine most locales will see frost, and concern is for perhaps pockets of black ice where freezing fog may result in Pioneer Valley through Monadnock Region and Central NH.  Any sun early Tue will quickly help to mix the atmosphere, tho Ci clouds will thicken and lower as midlvl moisture spreads NE across NewEng thru Tue.

Slug of moisture slated for Tue Ngt shud come in with progged vort max as referred to in first paragraph.  12Z GFS a bit drier than its preceding run, 12Z NAM not much more moist and still noticeably drier than GFS.  Canadian Ensembles and GFS Ensembles both lean toward wetter solution, while most guidance insists on quick solution.  Wet and quick both make the most sense with slug of isentropic lift intense thanks to tropical slug but quick moving embedded in the subtropical jet.  The net result shud be a shot of 1" QPF for most of Srn NewEng with locally higher amounts, then lesser amounts Nrn half of NewEng.  As warm and moist advection wanes Wed AM, rain will taper, tho quick progression of warmth and moisture aloft leaves behind the corridor of warm advection in the llvls, and this means plenty of moisture is left behind at 850 mb and below.  Hence, clouds linger thru most of day Wed tho a few breaks not impossible Wrn areas as sfc inverted trof/weak warm front moves E and brings westerly flow, while drizzle immediately behind rain assoc with shift of winds to the N and llvl cool advection shud be found in ME coastline.

Still will have sfc low assoc with llvl remnant of Norman that will eject off MidAtl coastline and pass SE of NewEng, while new shortwave induces sfc low development in the Great Lakes and drags cold front with multiple waves across OH and TN valley.  This front with waves will enter the I-95 corridor Thu Ngt and strengthening wave with tropical moisture will be rippling thru MidAtl Thu Ngt en route to NewEng for Fri.  This happens at the same time Nrn stream wave moves E, carrying cool air behind it, and this is enuf to at least peak interest in how the incoming cold air will interact with northward rippling moisture-loaded wave.  I say this because, at some point, these two features really should link up, but the question is how quickly does that happen?  The 12Z GFS is one of the quickest to merge, and while I do think the GFS tends to handle waves of fronts better than most of the guidance, the key here is more in the handling of the Nrn stream shortwave, which takes on a neutral/negative tilt at the end of this week but does so just a bit too far west on Thu to let the cold come flooding in as quickly as the new GFS would paint.  I think the end result is that the merger of cold and tropical occurs E of ME later Fri, and this means Nrn ME will be on-guard for wrap-around precip...and yes, perhaps snow...late Fri into early Sat.  Certainly something to watch carefully.

Another watcher will be the beginning of next week, which the GFS Operational has not been nearly as bullish on as its Ensemble member counterparts, but bullish may be the way to go for next Mon/Tue as polar vortex deepens over SCentral Canada before nudging east and quite literally helps to create its own cold air that should be quite eager to move into NewEng, with strong energy aloft and sfc baroclinicity ready to encourage sfc low development over or near Ern NewEng, and once again raising eyebrows for those interested in snow prospects for the North.

We'll see...plenty to work out between now and then.

Matt


THOUGH WARMTH REMAINS WITH NEW ENGLAND FOR THE MIDWEEK...FRIDAY STORM MARKS THE BEGINNING OF A SIGNIFICANTLY COLDER PATTERN

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

General Weather Summary:

The overall weather pattern will take a decidedly more winter-like appearance over the course of the next week.  Intense energy dropping south from the North Pole will deepen both the cold air and increase the potential for storm growth in the Eastern United States by the beginning of next week.  In the meantime, warm and rather tropical air has spread north along the Eastern Seaboard, and most of Southern New England will feel the difference Wednesday afternoon.

Overnight rains brought a sharp drop in precipitation amounts across Southeastern MA, but dropped over an inch of rain to Portland, ME, and vicinity.  These rains were associated with the remnants of what was once Tropical Storm Norman - a storm in the Pacific Ocean that carried moisture across Mexico, gained more moisture in the Gulf of Mexico though was not reclassified as a tropical system, pummelled the Texas coastline with tornadoes and flooding, then curled northeast over New England Tuesday night.  The slug of tropical warmth and moisture associated with this remnant, colliding with our cool fall air that was still in place, was truly the impetus in wringing out moisture.  Where the clash in airmasses continues - across Northeastern New England and especially Maine - clouds will hold firm, showers will only gradually taper through the afternoon, and temperatures will remain cool as a result.  Farther south, satellite imagery has clearly shown drier air moving into the Southern half of New England from the southwest, and this will help to poke holes in the cloud deck from late morning through afternoon.  With tropical air in place, just a little bit of sun will go a long way, boosting temperatures to over 70 degrees where the most sun is found!  With one weak upper level disturbance set to swing through Southern New England Wednesday afternoon, a shower or thunderstorm is possible later in the day in areas that see the warmest temperatures.

Wednesday night will remain dry and relatively mild, though our tropical air will provide sufficient moisture under partly cloudy skies for areas of dense fog to develop.  Fog and sun will therefore be found Thursday morning, and the next round of clouds will be on the move toward New England, well ahead of the next developing storm over the Mississippi River Valley, which will be a result of one chunk of substantial energy carving out a trough in the jet stream over the Central United States.  Remember that the jet stream is the fast river of air aloft that steers our storm systems and acts as a thermostat for the atmosphere, separating cold air to the north from warmer air to the south.  With a storm developing at the dip in these jet stream winds - the trough over the Mississippi Valley - it will be able to feed off of the difference between warmth and cool air, and will be driven by the strong, energetic jet stream winds aloft toward New England.  As clouds thicken from north to south during the day Thursday, showers will follow suit, with showers developing by midday in the north, then expanding over Central New England during the afternoon.  By Thursday evening and night, showers will expand into Southern New England.

All the while, the developing storm to our southwest will be strengthening and charging toward New England.  This should deliver a swath of rain, heavy at times, to New England on Friday, with gusty winds.  While it's evident that a period of windy and wet weather will affect New England on Friday, the exact storm track is still in question, which means wind direction and therefore duration of wet weather is still in question.  If the storm tracks directly over New England, a brief but intense period of rain would move through, accompanied by warm winds.  If the storm center should move just east of the region, however, northeast winds will blow, keeping New England cool and raw.  At this point, it seems as though a track over Eastern New England may be most likely - keeping most areas on the cool side.  Colder air will be poised to charge in behind this storm, and though it will also be drier air that will bring gradual clearing Friday night into Saturday for many areas, the State of Maine - especially Central and Northern parts of the state - may see at least snow showers continuing on the first half of the day Saturday.

Thereafter, expect dry conditions to begin Sunday - so...all in all...most of New England does enjoy a decent fall weekend.  That said, the next blast of energy - two strong disturbances merging from the Pacific and from near the North Pole - will be gathering strength and moisture across the nation's midsection.  Clouds will increase Sunday and showers may develop by evening from west to east.  This will set the stage for what will likely be a powerful storm for New England Monday into Tuesday.  With cold air prior to the storm, and more cold air on the backside of the circulation, the threat for more widespread snow is present across Northern New England at the beginning of next week.  This is a potential that needs to be monitored carefully for a possible early-season snow on especially the Northern Mountains.  Obviously, confidence in such a forecast at this point is still quite low, given that I'm still working out the details for the Friday storm, let alone one even farther out in time, but you come here to find out my thoughts, and now you have them!

Next week should be marked by much-below normal temperatures - perhaps producing record cold around midweek.

Enjoy your hump day.

Matt

Matt's Technical Meteorological Discussion:  Updated Wednesday, October 16 at 3:05 PM

'Tis the season for surges of winter amidst lingering tropical warmth and moisture, and NewEng shud see both in the coming week.  Tropical airmass in place as of this writing thanks to delivery by former TS Norman who chugged over NewEng last night dropping rainfall amounts over an inch to some, and under a quarter inch to others.  Nonetheless, the storm has left behind an appreciable chunk of tropical warmth directly from the Gulf of Mexico and areas with sun have seen corresponding quick temp rises.

Shortwave embedded in the flow to cross between 18Z and 00Z this afternoon and have adlibbed isolated shra/tsra with warmth and low level moisture in Srn NewEng, tho cov'g should be limited.  Enuf dry air aloft for breaks to remain in clouds overnight tho fog will be dense in many areas with relatively light wind and high dewpoints.

Fog and sun starts Thu before clouds advance along midlvl baroclinic zone stretched across Nrn NewEng.  Approach of shortwave energy to interact with this zone in generation of showers for Nrn NewEng by early afternoon, expanding S as cool front approaches from NW and baroclinic zone tightens.  Leading s/w ejects NE from base of Central US trof on Thu and fills showers and period of rain in across Srn NewEng Thu eve into the ngt.  Thereafter, attention turns to strong shortwave migrating rapidly E in Westerlies.  Tho this s/w will be strong, it will also be progressive until it reaches NE NewEng later Fri, where it interacts with colder air aloft and deepens/closes off NE of ME.  There has been some issue as to the path of assoc sfc low pressure center(s) with this vort max, more so with the secondary low than the primary, which will cut north of NewEng.  The secondary has been progged from NYS to offshore NewEng as a nor'easter (ECMWF) but consensus likely to be best, not to mention the solution of the GFS Ensemble mean - which places triple point low over Ern NewEng - inland - perhaps getting Cape Cod into warm air as it swings thru but bringing gale SE gusts to the mid and downeast ME coast and perhaps gale force SW gusts under the belly of the strengthening sfc low to SE NewEng.

As this storm wraps up while moving NE Fri Ngt into Sat, still feel there is enuf basis to include potential of snow in the fcst for Nrn/NE ME with wraparound precip early Sat.  While operational models have varied greatly for this time period, GFS Ensemble mean has stuck to its guns of keeping high chc pops in NE ME at the same time cold air in Srn Canada is ingested into storm center.  Additionally, with upper level low closing off, moisture wraps around back of circulation and will maintain chc snow showers in Nrn ME for Sat AM.  Precip also may end as a few flakes in Nrn mountains of NE VT/NH where upslope flow can generate enuf lift, but dry air quickly moving in behind storm by that point.  Ridging is quick to move back in aloft and this will mean cool but dry most of NewEng Sat into Sun.  Next s/w in line is one that recently ejected from the Aleutian low and will drop into Central US trof, ejecting NE into NewEng like its predecessor, but with enuf airmass modification for rain in all locales except perhaps in Nrn ME where warm and moist advection will ride overhead before llvl flow can swing out of the N and this means a brief pd of light WAA snow would be possible in Nrn ME later Sun ahead of the s/w.  Warm advection should win out Sun Ngt, however, with all areas going to liquid.

The real meteorological fun only grows more intense early next week, as a strong shortwave dropping south from the polar vortex near the North Pole will merge with a Pacific counterpart and amplify handily at the base of the trof to our west on Monday.  The trick here is that the storm Sun into Mon will have already yanked down a hearty chunk of cold air from Canada, and the motherload of cold will be heading east across the Midwest.  This will be another chunk of record cold in Iowa, and will end up spelling record cold for the Mid-Atlantic and at least some of the Northeast by the middle of next week.  But the transition to this cold will likely come with an intense cyclone as the upper low deepens and generates its own cold air through continued dynamic cooling over Southeastern Canada, and drives sfc cyclone development over or very near to NewEng on Monday.  This storm will already have picked up plenty of Gulf moisture during its amplification, and with the cold air to the north and west of the storm, sufficient baroclinicity will meet sufficient vorticity to generate a powerful storm whose circulation will tap the cold to our west and northwest.  The result should be enuf cold air meeting up with a wound up storm that will wrap significant mositure around its west side to generate snows from Nrn ME thru the North Country where upslope flow will play a significant role.  In fact, the situation looks quite favorable for accumulating upslope flow snows in esp the Green Mountains as cold advection meets with moisture on a strong NW flow.  While this will not spell snow for Srn NewEng, it will spell a great pattern for cold air - a prolonged NW flow at the sfc meeting up with an airmass to the tune of 12 C below normal, creating record low temperatures, especially by midweek when winds will weaken but WAA will not have begun yet, and overnight lows should plummet.

What could change this outlook?  Obviously storm track and timing of cyclogenesis is crucial.  Slightly farther east...or west...upsets how the cold air and the storm can interact and the wind direction.  This won't change the cold - that's coming - what it would effect is the potential for accumulating snow.  But at this point, I'd say it's certainly the best chance of snow the North Country has had since spring.

We'll keep an eye on it together.

Matt

Monday's Discussion:

1:40 PM:  Slow moving wx pattern has been northern stream dominated of late but that will change in the coming days as trof continues to dig in Wrn US and sends subtropical jet springing northward.  This subtropical jet is active with the remnant of Norman, a former tropical storm who churned across the Eastern Pacific before crossing Mexico, then regaining an impressive satellite signature over the Western Gulf of Mexico this weekend before making landfall early Monday into the Eastern TX coastline, where winds gusted in excess of 40 mph.  Torrential rain has been lifting north and will turn NE as it encounters the fast flow of the westerlies across the Midwest, and the vort max assoc with the remnant of Norman will charge NE and directly over Srn NewEng late Tue Ngt and Wed AM, bringing a shot of heavy rain with it.

In the meantime, high altitude Ci clouds will spill overhead in waves Mon Ngt as thicker moisture puts on the brakes crossing OH Valley, but dry air and light wind shud still allow for temps to fall quickly after sundown.  If enuf Ci spill overhead, my fcstd low temps will be a bit too warm, tho with Tds in the upper 20s to around 30, I'd imagine most locales will see frost, and concern is for perhaps pockets of black ice where freezing fog may result in Pioneer Valley through Monadnock Region and Central NH.  Any sun early Tue will quickly help to mix the atmosphere, tho Ci clouds will thicken and lower as midlvl moisture spreads NE across NewEng thru Tue.

Slug of moisture slated for Tue Ngt shud come in with progged vort max as referred to in first paragraph.  12Z GFS a bit drier than its preceding run, 12Z NAM not much more moist and still noticeably drier than GFS.  Canadian Ensembles and GFS Ensembles both lean toward wetter solution, while most guidance insists on quick solution.  Wet and quick both make the most sense with slug of isentropic lift intense thanks to tropical slug but quick moving embedded in the subtropical jet.  The net result shud be a shot of 1" QPF for most of Srn NewEng with locally higher amounts, then lesser amounts Nrn half of NewEng.  As warm and moist advection wanes Wed AM, rain will taper, tho quick progression of warmth and moisture aloft leaves behind the corridor of warm advection in the llvls, and this means plenty of moisture is left behind at 850 mb and below.  Hence, clouds linger thru most of day Wed tho a few breaks not impossible Wrn areas as sfc inverted trof/weak warm front moves E and brings westerly flow, while drizzle immediately behind rain assoc with shift of winds to the N and llvl cool advection shud be found in ME coastline.

Still will have sfc low assoc with llvl remnant of Norman that will eject off MidAtl coastline and pass SE of NewEng, while new shortwave induces sfc low development in the Great Lakes and drags cold front with multiple waves across OH and TN valley.  This front with waves will enter the I-95 corridor Thu Ngt and strengthening wave with tropical moisture will be rippling thru MidAtl Thu Ngt en route to NewEng for Fri.  This happens at the same time Nrn stream wave moves E, carrying cool air behind it, and this is enuf to at least peak interest in how the incoming cold air will interact with northward rippling moisture-loaded wave.  I say this because, at some point, these two features really should link up, but the question is how quickly does that happen?  The 12Z GFS is one of the quickest to merge, and while I do think the GFS tends to handle waves of fronts better than most of the guidance, the key here is more in the handling of the Nrn stream shortwave, which takes on a neutral/negative tilt at the end of this week but does so just a bit too far west on Thu to let the cold come flooding in as quickly as the new GFS would paint.  I think the end result is that the merger of cold and tropical occurs E of ME later Fri, and this means Nrn ME will be on-guard for wrap-around precip...and yes, perhaps snow...late Fri into early Sat.  Certainly something to watch carefully.

Another watcher will be the beginning of next week, which the GFS Operational has not been nearly as bullish on as its Ensemble member counterparts, but bullish may be the way to go for next Mon/Tue as polar vortex deepens over SCentral Canada before nudging east and quite literally helps to create its own cold air that should be quite eager to move into NewEng, with strong energy aloft and sfc baroclinicity ready to encourage sfc low development over or near Ern NewEng, and once again raising eyebrows for those interested in snow prospects for the North.

We'll see...plenty to work out between now and then.

Matt