Northeast Weather Blog

Strong clipper to bring accumulating snowfall

By: sullivanweather, 8:08 AM GMT on December 30, 2008

Current watches, warnings and advisories.


Eastern US current watches/warnings

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Forecast Discussion


Synopsis - Issued 12/30 @3:05am


Several areas of low pressure will move along a very fast west-east flow across the northern tier of the country into the Northeast. The first in this series of clippers is moving through the region at the time of this writing. The next, and most potent, will slide by Tuesday night and Wednesday, followed by another on Friday/Saturday and a fourth on Sunday.


Short-term - Issued 12/30 @3:05am



Snow showers and flurries had overspread much of the northern half of the Northeast as of late Monday evening in association with a rather potent clipper low moving across southern Canada. This system is moisture starved and would hardly be considered ‘potent’ in terms of accumulating snowfall, however, where it will be felt most is in the wind department. Flow at 850mb is in excess of 50kts across a good chunk of real estate with a strong 35-45kt boundary layer flow aligned out of the west-northwest. Given the strong cold air advection behind the cold front trailing south from the low center these winds should easily mix down to the surface and wind advisories have been posted just about region-wide, aside from Maine lying just outside of the belt of strongest winds located to the southwest. Combined with the light to, at times, moderate snow across upstate New York and northern New England traveling will become quite difficult, with occasional near-zero visibilities in blowing snow, especially across the higher terrain of the Adirondacks, Green and White Mountains. Also included are areas immediately downwind of Lake Ontario as the lake effect kicks in. This is where the accumulating snow will be found, on the order of 2-4” with less than an inch elsewhere across the region. Temperatures tonight are holding steady now that clouds have overspread much of the region but they will fall towards daybreak as deeper cold air moves in.


Much more of the same on Tuesday in terms of strong winds and lake effect/terrain enhanced snow showers. The clipper will transfer its energy to an area of cyclogenesis east of Newfoundland leaving behind little forcing outside of local enhancements and general cyclonic flow. Upslope areas of the North Country and around the Tug Hill Plateau should receive an additional inch or two of wind-driven snow. For most everyone else the skies will be partly cloudy but the big story will be the winds. Boundary layer flow will still be 30-45kts from I-81 on east across eastern New York and much of New England. Continued cold air advection and diurnal influences will drive these winds down to the surface in gusts that may very well exceed 50mph, especially in exposed/elevated areas. Temperatures will rise very little during the morning hours and will likely fall several degrees during the afternoon as the airmass aloft cools roughly 4-6°C through the course of the day. Highs will reach the upper 30’s to low 40’s along the southern coastal plain with upper 20’s to mid 30’s across the interior and along the northern New England coast. The higher terrain will likely see an all day drop in temperatures, beginning the day in the mid to upper 20’s then dropping to the upper teens by day’s end. There will be an increase in high cloudiness late in the day across the western portions of the region as isentropic lift ensues ahead of the next disturbance. A good time to keep an eye to the sky for sun pillars/sun dogs, always a winter sky treat. If these clouds move in early enough, before 2pm when the sun is at a high enough angle, a circumzenithal arc may be witnessed or other intriguing sun halos.

As night falls clouds will rapidly increase from the west, lowering and thickening during the evening hours. Light snow will break out by midnight across the Niagara Frontier and extreme northwestern Pennsylvania around midnight, spreading eastwards to cover much of the Finger Lakes region, Catskills, Allegheny’s and the northern tier of Pennsylvania by daybreak. Thereafter it will spread across southern/central New England during the day on Wednesday. The surface low looks to take a track from the Upper Ohio Valley and across southern Pennsylvania, with surface low reformation occurring just off the northern New Jersey Coast. As the low tracks across the region it will be deepening rapidly. Pressure falls from ~1002mb when it enters the region to ~988mb as it passes south of Cape Cod. Despite not having much moisture to work with (Precipitable water values around .25-.33”) strong frontogenic forcing along the north side of the tracks of the 850/700mb low couplet will make for very efficient precipitation generation. Also, unlike previous storms this season, strong UVM in the snow growth region (-15 to -20 microbars/sec) will make for increased fluff factor, leading to 15-18:1 snow:liquid ratios, especially in the axis of strongest frontogenesis, though, where this intersects with the immediate coast ratios will likely be lower due to warmer temps in the boundary layer, likely 10:1. Strongest model projected 2-D frontogenesis occurs along the New York/Pennsylvania border to the southern Catskills/Taconics and along the I-84 Corridor across southern New England. Model QPF has steadily increase in the lead up to this event and is now running around a third to a half an inch, with lesser amounts (<.25”) to the north and south of axis of heaviest precipitation. The southern cut-off should lie across the southern tier of Pennsylvania across to Atlantic City, New Jersey, where just a few scattered flurries and/or sprinkles will fall. To the north, the northern edge of the precipitation lines up from the southern Adirondacks eastwards to the Portland, Maine vicinity. A snow map will follow shortly to outline amounts, which should range from 4-8” across the area progged to receive the highest QPF. Lows Tuesday night will range from the teens and single digits across the far north to the 20’s and low 30’s across the southern interior and coastal plain. On Wednesday, temperatures remain steady or slowly fall across the south as arctic air pours into the region behind the departing low while across the north temperatures rise into the 20’s by noon and drop sharply by mid afternoon thanks to the arctic airmass. Winds will also become quite blustery once again thanks to aforementioned pressure falls and strong cold air advection.




Mid/long-term - Issued 12/30 @6:15am

Low pressure rapidly pulls towards Newfoundland Wednesday night as it bombs out to a 975mb storm center. Strong cold air advection will be left in its wake as 850mb temps drop from –15°C to –24°C, ushered in on a gusty north-northwesterly flow. Airmass is also very dry and given the short fetch, lake effect snows will be kept to a minimum, likely a multi-band event across central New York. There may even be a few ocean effect bands out over the Cape. Despite the overall lack of precipitation, with the very cold airmass in place and gusty winds over a fresh snow cover there will still be a host of problems to deal with. Lots of folks will be out and about due to the New Year’s holiday and it would be a good idea to pack a winter weather survival kit. On their own, temperatures will be very cold across the region, ranging from the upper teens to low 20’s along the coast, but inland it’ll be much worse. Here temperatures should fall into the single digits with the North Country likely falling below zero, by a good margin across the higher terrain too. In addition, the biting wind of 10-20mph will create wind chills close to zero along the coast and up to –30°F across the far northern interior. These winds will also create lots of blowing and drifting of snow. It may be a good idea to simply keep it indoors for New Year’s Eve this year. Ouch!


High pressure builds in on Thursday (New Year’s Day) with a slackening of the winds and a slight moderation of the brutal airmass overhead, except for over Maine where 850mb temps should fail to climb out of the –20°C range. Skies will become mostly sunny but temperatures at the surface will fail to respond to the weak January sun with highs running some 5-15 degrees below normal. The high will crest over the Northeast Thursday night with excellent radiational cooling conditions. Many locations across the northern interior will once again fall below zero with the remainder of the region in the single digits and teens.

The next system of concern moves towards the Northeast on Friday. Still much to be resolved with this one as the main pocket of energy still lies in the Gulf of Alaska. Recent model trends have been for a much less amplified storm and a lack of phasing with southern stream energy until it’s mainly east of the region. GFS remains steadfast in developing low pressure in the Delmarva vicinity Friday and moving it up the coast for a significant snowfall for the eastern half of the region into the first half of the weekend but other model solutions have trended away from this scenario and now depict more of a northern stream trough passage with cyclogenesis occurring south of Nova Scotia. As it looks currently, Maine stands the best chance at a significant snowfall with mainly light accumulations of snow all points west. Until this energy moves ashore the Pacific Northwest and comes under a better sampling from ob sites uncertainty will remain high. A weak transient ridge clears things out from west to east Saturday into Saturday night, though it will be blustery before this high arrives, then the next system moves in by Sunday afternoon spreading more snow showers to the north with a light mix or rain showers to the south.

Looking ahead into next week, a southern stream disturbance looks to make a run at the Northeast by next Tuesday. This one should have much more moisture to deal with than any of the first 4 systems to affect the region over the next 7 days and will be one to watch.



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Radar: Northeast Region Loop

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Current snowcover

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Local SST's

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Ferndale, NY climagraph

***Climagraph has been discontinued and will return at the beginning of 2009 with the location of Yulan, NY***
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2008-09 Winter Forecast


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Updated: 2:38 AM GMT on January 02, 2009

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Near-record warmth today; Winter to settle back in this week

By: sullivanweather, 9:39 AM GMT on December 28, 2008

Current watches, warnings and advisories.


Eastern US current watches/warnings

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Forecast Discussion


Synopsis - Issued 12/28 @4:40am


Deep southerly flow will have temperatures approaching record levels on Sunday before a sharp cold front passes through the region during the afternoon, bringing high winds to the north. During the upcoming week there will be three trough passages, each one bringing progressive colder air in their wake, and each progressively stronger. The third in the series of these troughs may become a significant winter weather event to open the New Year.


Short-term - Issued 12/28 @4:40am



A strong inversion is beginning to lose its grip on the Northeast as a strong southerly push of mild air continues to surge into the region. However, until this inversion mixes out this morning, it will create some problems with low clouds and locally dense fog. The temperature contrast across the Northeast is rather large this morning thanks to the cold air damming east of the Appalachians. Erie, PA is reporting a temperature of 66°F at the time of this writing, while to the east of the mountains State College is a chilly 28°F! Some of these colder locations will have glazing issues due to freezing fog and patchy freezing drizzle (not to mention a very cold ground). Above the inversion skies have cleared allowing for some areas to decouple and experience radiational cooling, hence the amazing temperature disparities. The warm air will eventually win this battle as 50-60kt low-level jet will adequately mix into the boundary layer this morning, eroding the low clouds/fog and send temperatures soaring to near record levels. There will be breaks of sun, especially along the coastal plain, that will help temperatures achieve these lofty heights. All this occurs today ahead of a sharp cold frontal boundary that will push into western sections of the region by mid-morning and blow across the remainder of the Northeast this afternoon and evening. Much of the energy/forcing associated with this trough will move by well to the northwest of the region, leaving little, if any, precipitation along its flanks. Scattered showers will do for most areas today, likely within an hour or two of the frontal passage. The most fanfare from the front will be in the form of strong winds, especially across the northern half of the region. Strong cold air advection and rapid pressure rises will lead to mixing down of the 50kt low-level jet into the boundary layer. Across the higher terrain winds of 25-40mph with gusts to 60mph will be common while the lower elevations see 20-30mph winds with gusts to 50mph. Further to the south the winds won’t be as strong, around 15-25mph with gusts to 40mph. Highs will likely be early in the day across the western half of the region, with many areas likely at their highs or the day currently. Here temperatures will remain in the 50’s and 60’s until the frontal passage, then begin to fall into the 40’s after the fontal passage. Across the east, temperatures will quickly rise once the inversion is broken, climbing into the mid 50’s to low 60’s along the coastal plain and southern interior by noon. Only across far northern New England will temperatures fail to crack 50°F.

Cold air continues to pour into the region tonight on a gusty, but diminishing, westerly wind. 850mb temperatures, which began the day above 10°C, will fall to –10 to –2°C from northwest to southeast across the region by daybreak. Skies will be partly cloudy away from the mountainous terrain and lakes where a few scattered snow showers may drift by from time to time. Temperatures fall back into the 20’s across the interior with 30’s along the coastal plan and 40’s in the urban centers.

Monday begins mostly sunny region-wide, aside from a few lingering lake flurries. Mid/high clouds will increase during the afternoon due to weak isentropic lift generated by a potent but moisture-starved clipper system diving into the Great Lakes. Temperatures will remain above normal, with highs around 50°F in the urban centers of New York and Philadelphia and along the southern Jersey Coast, with 40’s elsewhere along the coastal plain and 30’s across the interior. Winds will remain out of the west around 10-20mph.

Aforementioned clipper system moves across central Ontario and southern Quebec Monday night spreading snow showers across the North Country with just a general increase in cloudiness across the south. Temperatures will continue to average 5-10 degrees above normal with lows in the 20’s across the interior and 30’s along the coastal plain.


Mid-term - Issued 12/28 @4:40am



Much cooler air arrives in the wake of the clipper as 850mb temps drop to –5°C to –15°C from south to north on Tuesday. This should drop temperatures back to seasonal averages to close out December. Cyclonic flow will keep snow showers going over the upslope regions of northern New England while the remainder of the region remains dry. Quickly on the heels of the first clipper system in this fast zonal flow is the next one, moving into the Northeast late Tuesday night and Wednesday. This next clipper has a bit better dynamics to work with and although the atmosphere will still be parched, it will still manage to squeeze out an area of steady light snowfall. This clipper also looks to take a track a bit further to the south, across the Niagara Frontier and off the Jersey Coast. In doing so, it will acquire more moisture, leading to light to moderate snowfall accumulations across New York to eastern New England. Just a little sometime to keep an eye on before the next system of concern moves towards the Northeast by week’s end; more on that later.


Long-term - Issued 12/28 @4:40am



High pressure builds into the Northeast on Thursday, with temperatures returning back to below normal readings as the progressively colder air follows behind each clipper. What follows for Friday and Saturday is a very complicated progression of complex low pressure moving from the Upper Midwest to the Ohio Valley and eventually off the coast of the Northeast by Saturday. That’s the general thinking right now behind what will become of a significant shortwave that will slam ashore the Pacific Northeast Coast on Wednesday as it approaches the region. There will be plenty of cold air in place ahead of the storm, but depending on where it wraps up will ultimately determine precipitation type here in the Northeast associated with the system. Some models predict a Miller type-B scenario with the primary low pressure transferring energy to a coastal low off Delmarva that would bring significant snows, especially to the interior, with a mix or rain along the immediate coast. Others depict a stronger primary low wrapping up into the Great Lakes and a mix to rain scenario for many locations as warm air surges up the East Coast. Trend of the last two winters would be for the latter to happen, but given the zonal flow in place ahead of the storms’ arrival would argue for the system to dig further southeast before wrapping up, hinting at the Miller type-B scenario. Either way, models all agree that this storm will have a high impact on the sensible weather here in the Northeast as heavy snows will present the obvious problems and heavy rain may lead to more flooding concerns, though how much of the snowpack survives after this most recent warm up remains to be seen.


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Radar: Northeast Region Loop

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Current snowcover

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Local SST's

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Ferndale, NY climagraph

***Climagraph has been discontinued and will return at the beginning of 2009 with the location of Yulan, NY***
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2008-09 Winter Forecast

Updated: 9:17 PM GMT on December 28, 2008

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Winter returns with a vengence

By: sullivanweather, 9:13 AM GMT on December 16, 2008

Current watches, warnings and advisories.


Eastern US current watches/warnings

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Forecast Discussion


Synopsis - Issued 12/16 @4:15am


An active week of weather of the wintry kind is shaping up for the Northeast. Three separate significant areas of low pressure will deliver mainly snow to the north and a mixture of precipitation type across the south. Following the third system temperatures will fall well below normal as we head into Christmas week.


Short-term - Issued 12/16 @ 4:15am


A sharp cold front, responsible for some dramatic temperature changes across the country, is currently pushing offshore and south of the region. Though not as potent now, it will still manage to drop temperatures low enough to change the mild showery weather of the previous couple days to a colder, snowier, icier scenario for the week to come. As this front has pushed south it has become aligned to the upper level flow, becoming anafrontal; meaning some or most of the precipitation associated with the front is falling behind it. This precipitation will gradually change over to snow, sleet and freezing rain from northwest to southeast as the colder air filters into the region. The front is also in the process of becoming quasi-stationary, just south of the region, as it banks up against the developing Southeast ridge. For the remainder of the overnight into Tuesday morning precipitation will continue across the southern half of the region, slowly changing from rain to a wintry mix, then to snow. Some light accumulations of snow and ice can be expected before precipitation tapers to flurries and freezing drizzle by early afternoon. However, as quickly as one impulse departs, another will be fast to fill its void and precipitation may break out once again around dusk in advance of the next wave of low pressure, likely as snow or a wintry mix. To the north, the day will be spent partly to mostly cloudy, mainly mid/high level clouds as upper jet streaks by overhead. A few light lake effect snow flurries may drift by with conditional instability parameters. Temperatures will remain in the 20’s across the north, with 30’s to the south and along the coastal plain. Winds will be out of the northwest around 5-10mph.

The next in a series of low pressures to ride up along the stationary boundary will move into the Northeast via the Ohio Valley Tuesday night. Isentropic lift (south) and mid-level frontogenesis (north) appear to be the main precipitation producing mechanisms with this system as it quickly moves through the region. There’s a weak cold air damming signature in the pressure/thickness fields thanks to a 1036mb high pressure over northern Maine, which should help to lock in the cold air in the boundary layer. Aloft, a good push of warm air advection should create a layer of above freezing air that will change snow over to sleet and freezing rain across much of Pennsylvania, south-central/southeast New York and southern New England away from the immediate coast. To the far north this looks to be mainly a snow event with light to moderate accumulations while along the coast (Maine excluded) temperatures in the boundary layer should sufficiently warm to bring this region mainly rain, although a few pockets of sleet may mix in at times. Low pressure rockets offshore on Wednesday around the noon hour, as much of the precipitation will have moved into New England by this time. This should be an advisory level event for much of the region away from the coast with the higher terrain locales of the Adirondacks, Green and White Mountains possibly looking at a low end warning criteria snowfall of 5-8”. Once again, with marginal parameters for lake effect snows there will only be a few flurries and scattered light snow showers off the lakes in response to the weak cold air advection behind the system. Temperatures overnight Tuesday will range from the teens north, 20’s south and 30’s coast. On Wednesday highs climb into the 20’s north, 30’s south, 40’s coast.




Mid-term - Issued 12/16 @4:15am



High pressure builds into the Northeast Wednesday night and Thursday, allowing skies to clear some and ending the light lake effect snows. Temperatures will average close to seasonal norms. The break between systems will be brief as high cloudiness begins to spill into the Northeast Thursday night as the next in a line of systems rapidly begins to organize over the Midwest. This second system appears to be much stronger, aided by a potent pocket of mid-level vorticity and dynamically driven, as it will be working with a 170kt jet streak at upper levels. Banana high wrapped around the northern semi-circle of the storm will do its best to try and deflect the storm eastwards rather than allowing it to move northeastwards and will also lock cold air into the Northeast east of the Appalachians. Preliminary QPF amongst the models is well agreed upon, ranging from a half to an inch and a quarter, easily a warning criteria event for much of the interior. Since this storm will be a fast mover it stands to reason that there will be heavy precipitation rates with this one. As always, it seems, there will be a transition zone to deal with, likely lined up somewhere across the southern interior. The storm moves offshore Friday afternoon/evening with scattered snow showers left in its wake. Behind the storm the frontal boundary will make a push further to the south, allowing high pressure to build in on Saturday with a deeper push of cold air.


Long-term - Issued 12/16 @4:15am



The third, and perhaps strongest, area of low pressure will head towards the Northeast late Saturday night and Sunday. This time around, instead of sending a piece of energy off the western trough towards the region, the entire trough looks to head east as it's replaced by another digging trough off the Pacific Northwest coast. Low pressure will form in the Southern Plains as a ~1050mb arctic high pressure builds into the Northern Rockies, whose ridge axis extends east-west across the US/Canadian border, a classic set-up for a major winter storm. Once again, this system will be aided by an anomalous 170kt jet stream over the eastern half of the country. There will also be a deeper cold airmass in place over the Northeast ahead of this storm, though it would be hard to imagine at least some of it not being displaced by the strength of the thermal advection ahead of the storm. Regardless, snow should break out across the region, likely changing to a mix or rain across the south. If everything comes together correctly, this could be quite a snowstorm for the region, especially upstate New York and northern New England. Lots of time to watch this one but being that it will be the weekend before Christmas, a big traveling weekend, preparations should be made now in the event this one rolls through as fierce as models prog the system to be. Surely, updates will follow. The storm wraps up off the New England coast on Monday as the rest of the country finds itself in the deep freeze. Global medium range models unanimously agree that the 850mb 0°C isotherm will extend from the Southeast Coast, across the Gulf Coast into northern Mexico then across the four-corners region to the California Coast. Quite the cold snap!


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Radar: Northeast Region Loop

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Current snowcover

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Ferndale, NY climagraph

***Climagraph has been discountinued and will return at the beginning of 2009 with the location of Yulan, NY***
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2008-09 Winter Forecast

Updated: 10:20 PM GMT on December 16, 2008

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La Nina déjà vu?

By: sullivanweather, 10:27 AM GMT on December 13, 2008

Current watches, warnings and advisories.


Eastern US current watches/warnings

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Forecast Discussion


Synopsis - Issued 12/13 @5:30am


High pressure will build over the Northeast and move offshore this weekend, bringing a marked warm-up on Sunday in return flow. The next cold front arrives Monday night and Tuesday and becomes quasi-stationary, just south of the region. Thereafter, several waves of low pressure will ride along this boundary delivering mainly wintry precipitation to the north and a mix or rain to the south.


Short-term - Issued 12/13 @5:30am



Sprawling 1030mb surface high pressure with a north-south ridge axis will build across the southern Mid-Atlantic and move off the Eastern Seaboard this evening. Any lake flurries will come to an end during the morning and elsewhere skies will be mostly sunny through noon. High clouds begin to spill into western New York and Pennsylvania during the afternoon making glare a problem on east-west routes. For those not driving, keep an eye out for sun dogs and pillars if high clouds should happen to move into your area. Despite the abundant sunshine it will be very chilly across the region. It barely cracks freezing along the southern coastal plain while much of the interior remains in the 20’s. Northern New York and New England will only manage to climb into the teens after a start in the single digits where hundreds of thousands are still without power.

It will be one more very chilly night across upstate New York and much of New England, although clouds moving in from the west should cut down the free fall at some point during the overnight. Warm air advection will begin in earnest and 850mb temperatures climb above freezing all the way to the New York/Pennsylvania border by daybreak, putting an early halt on the drop in temperatures across Pennsylvania and New Jersey. Other than New Hampshire and Maine, much of the region will have their lows at or before midnight with slowly rising temperatures thereafter. Lows will bottom out in the upper 20’s and low 30’s across western Pennsylvania and along the southern coastal plain. Across Pennsylvania to the northern coastal plain lows will be in the upper teens to low 20’s. Upstate New York and northern New England will bottom out in the single digits and low teens.

A strong blizzard moves into the Northern Plains on Sunday as the high offshore builds. The southerly flow between these large synoptic features increases across the Northeast, with frontogenesis occurring at the nose of higher theta-e air punching through the Great Lakes region. The eastern end of this developing warm front may bring some light wintry mix to northern New York and New England late Sunday afternoon and Sunday evening. Meanwhile, fog and drizzle, even some patchy freezing drizzle, will become an issue across the remainder of the interior, especially over the recently laid down ice/snow pack. Highs will climb into the 40’s and low 50’s across the south and along the lake plains with lows in the 30’s and 40’s. The North Country will stay in the upper 20’s and 30’s for highs with little change in temperature Sunday night.


Mid-term - Issued 12/13 @5:30am



Warm front will be north of the region, well into Canada on Monday with deep southwest flow aloft. There will be low clouds and some drizzle under the inversion across the interior with some breaks of sun along the coastal plain. Rain enters the western third of the region as a strong cold front approaches in the afternoon. Temperatures will be some 5-10 degrees above normal. Front continues to slide southeast Monday night, becoming increasingly anafrontal as it aligns to the flow aloft. Rain will change to snow from northwest to southeast, across the Appalachians, much of upstate New York and northern New England during the overnight and end as flurries down to the coast on Tuesday. Temperatures will drop back to seasonal norms, or maybe a few degrees below, after the passage of the front.


Long-term - Issued 12/13 @5:30am



Aforementioned front sags south of the region before stalling on Wednesday. The large trough in the Western US will then start to send pieces of energy rippling along this boundary, which will extend from Colorado to the northern Mid-Atlantic. Models in somewhat fair agreement, other than minor timing and track differences. The first disturbance looks to arrive Wednesday night and the second on Saturday. There should be enough cold air across the region for the first system to bring mainly wintry precipitation types to the region, except for along the coastal plain and just west of the Laurel Highlands. The second system looks warmer and the transition zone may be further inland. Unfortunately, the second system also looks to bring more QPF for a region that could desperately go without another ice storm. In fact, the pattern beginning midweek looks very much like last year’s textbook La Nina set-up and the strength of the Southeast ridge will have to be monitored as this feature will have the most bearing on storm track in the coming week leading up to Christmas. If Santa wants to have a smooth landing, he’ll have to hope that ridge doesn’t get too strong.


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Radar: Northeast Region Loop

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Current snowcover

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Local SST's

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Ferndale, NY climagraph



*averages used are from WU Monticello data minus one degree on highs and lows to better represent my local region. Actual temperatures are from my PWS.
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2008-09 Winter Forecast

Updated: 10:31 AM GMT on December 13, 2008

Permalink

Severe nor'easter to pound the region

By: sullivanweather, 9:52 AM GMT on December 11, 2008

AN EXTREMELY DANGEROUS, LIFE-THREATENING SITUATION IS DEVELOPING OVER THE INTERIOR OF THE NORTHEAST. RESIDENTS HOULD PREPARE FOR A DEVASTATING ICE STORM THAT WILL BRING DOWN NUMEROUS TREES AND POWER LINES. SOME AREAS COULD BE OUT OF POWER FOR SEVERAL DAYS AS UTILITY CREWS STRUGGLE TO GET A FOOT HOLD ON THE SITUATION. ANYONE IN THE AREAS EXPECTED TO RECEIVE HEAVY ICE ACCUMULATIONS SHOULD TAKE THE NECESSARY STEPS TO ENSURE THEIR SAFETY. TRAVEL IS HIGHLY DISCOURAGED THURSDAY AFTERNON THROUGH FRIDAY MORNING AS IT WILL BE VERY DIFFICULT, IF NOT IMPOSSIBLE. A VERY COLD AIRMASS WILL FOLLOW THE STORM LASTING INTO SATURDAY. TEMPERATURES BOTH FRIDAY AND SATURDAY NIGHTS ARE EXPECTED TO DROP INTO THE TEENS AND SINGLE DIGITS IN THE AFFECTED AREAS WHICH MAY PRESENT LIFE-THREATENING CONDITIONS FOR THOSE WHO RELY ON ELECTRICTY FOR HEATING PURPOSES.


Current watches, warnings and advisories.


Eastern US current watches/warnings

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Forecast Discussion

If there ever were a time for a thorough in depth forecast, this would be it. A crippling winter storm is on the doorstep of the Northeast that will have wide ranging effects. Across the far interior as much as a foot of snow could fall, while along the coast flooding rainfall and strong winds will create their own set of problems. However, by far, the worst conditions will be just inland of the coast where a devastating ice storm is shaping up that could leave some areas without power for several days, maybe even a week as utility crews will be stretched thin due to the widespread nature of this storm. Very cold air follows in behind the storm that could create life-threatening conditions for those without power. Residents are urged to heed the warnings of local officials, keep tuned to the very latest on the storm and take the necessary precautions to ensure the safety of themselves and their families. I repeat, this is a life-threatening situation! Milder conditions return for the second half of the weekend into early next week that will give folks time to recover. Another frontal boundary moves through the region midweek with a return to wintry conditions.


An anomalously strong upper level low pressure is currently tracking along the north-central Gulf Coast early this morning, responsible for accumulating snows in the Deep South, even to the Texas Coast! In addition winter storm warnings have been issued for much of central Mississippi and east-central Louisiana where up to 6 inches of snow may fall. Here in the Northeast a cold front has been slowly pushing south across the region over the previous 24 hours and has now become stalled just offshore. This action has allowed for cold air to bleed southward, into the region, setting the stage for the upcoming winter storm.

Meteorologically speaking, this storm is almost as bad as it gets. Offshore, an anomalously strong deep layer ridge will be unyielding to the advancing low pressure, tightening the gradient along the Eastern Seaboard and promoting the development of a very strong low-level jet, in excess of 75kts! This flow will be aligned to the tight thermal gradient set up along the coast thanks to the quasi-stationary front offshore allowing for intense frontogenesis to develop. As low pressure moves northeast out of the Gulf and across the Southeast it will garner tremendous amounts of moisture. Precipitable water values will range from 2-4 standard deviations above normal and it’ll just be getting started. Upon reaching the Delmarva Coast, the low pressure will also acquire moisture from the Atlantic and focus this moisture into the frontogenesis band leading to impressive QPF. Additional forcing from the development of a coastal front will only add to the misery, where as much as 4” of rain could fall. This storm will be just as remarkable in the mid and upper levels. Strong vorticity advection will further enhance lift as will impressive divergence at upper level. This will be a very dynamic system too, with the region sitting square in the right rear quad of a 170kt jet over southeastern Canada. Essentially strong lift will exist throughout the entire vertical atmospheric profile.


Now to the meat and potatoes of the storm, who gets what and how much. Along the immediate coast up to southern New England, this is a rather straight forward forecast. Rain, already falling at the time of this writing, will become steadier and heavier as the day progresses. By this evening rainfall rates will reach an impressive quarter to half inch per hour, especially in/around the location of the developing coastal front. This will lead to flooding of poorly drained areas, ditches, parking lots along with rapid rises on rivers and streams, which very well may come out of their banks during the overnight hours. Minor to moderate flooding can be expected, especially along the flashier waterways. Rain will taper off to showers before daybreak and end as scattered snow showers as cold air infiltrates behind the departing low. There will also be a high wind threat in the warm sector of the storm. Some of the strong winds in the low-level jet may get mixed down into the boundary layer, especially if convection develops. This may cause downed trees in highly saturated soils. This threat looked much higher yesterday but with the surface low now expected to take a more easterly track the threat has diminished some. Now, on to the fun part of the forecast; the interior.

Across the far interior, from the Appalachians, to the Finger Lakes region of New York, northeastwards to the Adirondacks and northern New England, this will be mainly a snow event, although some sleet may occasionally mix in along the southern boundary of this region. Strong mid-level frontogenesis will efficiently wring moisture out of a rich atmosphere. Without getting into too much detail, potential exists for up to 6-12 inches of snow with the highest amounts extending from the eastern Finger Lakes into the southern Adirondacks, northern Green and White mountains and northern Maine and lesser amounts towards north-central/western Pennsylvania west of Williamsport where 2-6 inches of snow is possible. There will be a very sharp gradient along the northern edge of the precipitation shield as northerly boundary layer winds and confluent flow aloft effectively saps the atmosphere of lift/moisture.

The worst of the storm will extend from northeast Pennsylvania, including the Poconos, into east-central New York, central New England, along the Mass Pike and into central Maine. Here a myriad of precipitation types will fall and in heavy amounts. There are still lots of fine-tuning to be had to the forecast here and an update or two will follow, if time allows. What it boils down to is a prolonged period of snow, sleet and freezing rain (more sleet/snow to the north, freezing rain to the south) as the boundary layer/ageostrophic flow drain shallow cold air into the region while impressive thermal advection aloft pushes temperatures in the 925-800mb level above freezing. Strong frontogenic forcing will produce exceptional UVM leading to heavy precipitation rates and devastating amounts of ice accretion. There are some caveats, though, that will preclude this from being a truly crippling event. For one, the shear rate of precipitation will lead to ice accretion rates less than ideal for heavy icing, as there will be some level of run-off before the rain is able to freeze on contact. Another thing to consider is the strength of the thermal advection pushing into the region, which, with marginal temperatures, may allow for surface temperatures in localized regions to climb above freezing for a short period of time cutting down on the allowable time for ice accretion. However, with that being said, there will be areas that will stay below freezing for this entire event leading up to an half inch to an inch or more of ice accretion. This amount of ice will easily bring down numerous trees and power lines and cause major disruptions to travel along area roadways. Travel is highly discouraged across these areas, not just for the ice on the roads, but the possibility for impassible roads due to debris (falling trees/branches). More on this at bottom. Precipitation will begin during the late morning and early afternoon hours and continue straight through the night. After midnight, as the low pressure begins pulling east of the area and a deeper layer of cold air penetrates south, precipitation will change over entirely to snow and may accumulate 2-6” in an impressive trowal/deformation band expected to develop along the backside of the storm. This snow will taper from southwest to northeast during the day on Friday.

This is a very dangerous storm and cannot be stressed enough. Preparations should be rushed to completion during the morning hours today before the storm begins to get a stranglehold over the region. Supplies of non-perishable foods should be purchased in the event of a prolonged power outage, which is a very real possibility. Due to the widespread nature of this storm utility crews may have their work cut out for themselves and will be stretched thin. In these cases they’re likely to service the more highly populated areas first, so those living in rural locations that lose power may do so for several days as crews try to keep up. Other factors need to be considered as well. Those that rely on electricity for heat may have to suffer through two excruciating nights of cold weather as temperatures on both Friday and Saturday nights are expected to drop into the teens and single digits. Also, those will electric well pumps need to prepare by bottling water in the event of a prolonged power outage. This storm is not to be taken lightly and may become a life-threatening situation for those left unprepared. Do the right thing and make sure you have all the necessary supplies in the event of an emergency to keep yourself and your family safe! There’s also an increase in carbon monoxide related deaths in these situations. Be mindful if using other means of heating!




Mid and long term forecast to follow later

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Radar: Northeast Region Loop

NE radar

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Current snowcover

Northeast Snowcover


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Local SST's

Northeast SST's

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Ferndale, NY climagraph



*averages used are from WU Monticello data minus one degree on highs and lows to better represent my local region. Actual temperatures are from my PWS.
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2008-09 Winter Forecast

Updated: 6:22 PM GMT on December 12, 2008

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Life-threatening ice storm to arrive Thursday and Friday

By: sullivanweather, 2:14 AM GMT on December 09, 2008

AN EXTREMELY DANGEROUS, LIFE-THREATENING SITUATION IS DEVELOPING OVER THE INTERIOR OF THE NORTHEAST BEGINNING TOMORROW LASTING INTO SATURDAY. RESIDENTS HOULD PREPARE FOR A DEVASTATING ICE STORM THAT WILL BRING DOWN NUMEROUS TREES AND POWER LINES. SOME AREAS COULD BE OUT OF POWER FOR SEVERAL DAYS AS UTILITY CREWS STRUGGLE TO GET A FOOT HOLD ON THE SITUATION. ANYONE IN THE AREAS EXPECTED TO RECEIVE HEAVY ICE ACCUMULATIONS SHOULD TAKE THE NECESSARY STEPS TO ENSURE THEIR SAFETY. TRAVEL IS HIGHLY DISCOURAGED THURSDAY AFTERNON THROUGH FRIDAY MORNING AS IT WILL BE VERY DIFFICULT, IF NOT IMPOSSIBLE. A VERY COLD AIRMASS WILL FOLLOW THE STORM LASTING INTO SATURDAY. TEMPERATURES BOTH FRIDAY AND SATURDAY NIGHTS ARE EXPECTED TO DROP INTO THE TEENS IN THE AFFECTED AREAS WHICH MAY PRESENT LIFE-THREATENING CONDITIONS FOR THOSE WHO RELY ON ELECTRICTY FOR HEATING PURPOSES. MORE WILL FOLLOW LATER TONIGHT AND THURSDAY AS THE COMPLEX NOR'EASTER MOVING TOWARDS THE REGION IS BETTER RESOLVED BY THE FORECAST MODELS.

Current watches, warnings and advisories.


Eastern US current watches/warnings

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Forecast Discussion


Synopsis - Issued 12/08 @9:15pm


A wild week of weather in upcoming for the Northeast featuring several large temperature swings and, perhaps, two significant storm systems. The first storm moves through the Northeast on Tuesday and Wednesday, bringing mostly rain to the region as it moves through after the passage of a strong warm front. The second low pressure could come barreling up the coast late Thursday and Friday, delivering a snowstorm to portions of the interior with rain along the immediate coast.


Short-term - Issued 12/08 @9:15pm


A strong (~1035mb) surface high pressure currently resides over the Northeast, providing mostly clear skies and light winds, allowing for strong radiational cooling. Temperatures are plummeting early this evening with most of upstate New York and central/northern New England already down into the teens and single digits. Further to the southwest the first signs of frontogenesis that will become a rather pronounced warm front is already occurring. Light snow/sleet is trying to develop over extreme southwestern Pennsylvania where clouds are keeping temperatures held in the 20’s. Since the airmass over the region is extremely dry it remains to be seen how much of this is actually reaching the ground. As the high slips off the coast tonight and winds turn to the south and clouds increase, temperatures are likely to rise overnight across most of the region with the exception being over the state of Maine where the surface high will hold on just a bit longer. Along the northern flanks of the warm front frontogenic forcing and strong isentropic lift will manage to squeeze out occasional snow showers in the dry airmass. These will transition into sleet and freezing rain across western Pennsylvania and New York right up to the Niagara Frontier as above freezing air moves atop the colder boundary layer. Snowfall tonight should be very light, generally under 2”, and confined to the region from the south shore of Lake Ontario to the Adirondacks. Some precipitation may sneak over the Appalachians but the increasingly dry airmass as one heads east should effectively end this threat.

Southerly flow intensifies on Tuesday as the high pressure moves offshore. The warm frontal boundary will push north with precipitation overspreading northern New England. By noon 850mb temps over 0°C will extend from the southern Tug Hill Plateau to the greater Boston, MA area and by evening only extreme northern New England will still be in the cold sector. Across the far north, along the border with Canada, snowfall amounts will range from 1-3” by evening. Just south of the warm front, thermal profiles suggest a mixing of sleet and freezing rain from the southern Adirondacks to the southern Green and White mountains. A few isolated pockets of freezing rain will also be seen in the northern Berkshires and some of the deeper valleys in the Catskills. Ageostrophic flow indicates a several hour period of east to northeast winds at the surface below the inversion that should help to lock in some cold air initially but the warm surge coming from the south will eventually win out and the entire column should warm above freezing during the overnight hours on Tuesday. Deep southwesterly flow eventually draws in enough Gulf of Mexico moisture to moisten up the atmosphere allowing for rain to overspread much of the Northeast by Tuesday night.

There will be a couple waves of low pressure to ride north along the frontal boundary, each one bringing a quarter to three quarters of an inch of precipitation. The first will move through Tuesday during the overnight and the second Wednesday afternoon and evening. Behind the first low the frontal boundary will start to make some eastward progress so that by the time the second low arrives, the transition zone will once again bisect the region. Rain will turn back over to snow from northwest to southeast during the day on Wednesday, though not likely in time for the coastal plain to see any of the white stuff before the precipitation ends during the evening hours. Temperatures will rise into the 50’s across the southern half of the region and up along the coastal plain to the Boston, MA region by Wednesday afternoon as the warm sector moves in. Further north it will be much harder to mix out the strong inversion so temperatures should only rise into the 40’s (mid-upper 30’s across the far north/higher terrain). Areas that have deep extensive snowpacks (Tug Hill, northern New England) should easily be able to handle the expected QPF from this storm without much concern for flooding. Areas where the snowpack is less extensive should see most of it melt off. Combined QPF and melting snow may cause some minor flooding concerns but since the precipitation will be spread out over a 24-30 hour period the flood threat will be minimal. Strong winds may become a concern across the New England Coast as the inversion eventually mixes out. With a 50-70kt low-level jet expected to develop and the warm sector expected to move in, some of these winds may find their way down to the surface, especially along the Maine Coast where some higher terrain exists.


Mid/long-term - Issued 12/09 @4:30am


Nor'easter - potential impacts




The surface cold front will become hung up along the coast Wednesday night, becoming quasi-stationary as it aligns to the flow aloft. There will be some moisture streaming northeastwards along the front that should produce scattered showers of rain (along the coast) and snow (inland). What follows is a very complex scenario that will likely bring a few extra grey hairs upon forecasters noggins by the time all is set and done. The front itself will become ‘stretched’ as the northern stream disturbance races off in the 150kt jet towards the Labrador Coast. In doing so a strong area of vorticity (the southern stream disturbance) with break off, in essence, becoming cut-off from the main flow and be left behind to fester along the Gulf Coast. Cyclogenesis will occur, in response, in a region ripe with moisture. As low pressure forms a northern stream disturbance will drop into the upper Great Lakes and serve as the kicker, eventually lifting the low out of the Gulf. The mid-level disturbance will open and move northeastwards, with the surface low, along the quasi-stationary boundary set up along the Eastern Seaboard. Here’s where it gets tricky and models diverge with some taking the low on a more easterly trek and others moving the storm along a track favorable for big time snows across the interior. What will ultimately decide where the low tracks is the level of phasing between the northern stream kicker and the southern stream low and where this phasing occurs. What is agreed upon is that there will be a very sharp cut off along the northwestern edge of the precipitation field so not all of the interior is subject to seeing this storm and many locales will remain dry for the entire event. The storm will be moving very quickly once caught up in the very fast flow aloft so it won’t have much time to produce but strong frontogenesis fields and anomalously high precipitable water values suggest that while the storm is producing it will be doing so efficiently and heavily. Areas that do manage to see snow from this system could have it adding up very quickly and travel will become difficult, if not, impossible for a time during the height of the storm. High pressure builds in quickly behind the storm over the Mid-Atlantic with 850mb temps falling to –6 to –12°C from south to north over the region. Lake effect behind the storm will be minimal but present and a few inches of snow may fall over the snowbelts before flow goes anti-cyclonic and inversions lower.


Heights build rapidly over the second half of the weekend as a major pattern shift begins to take effect on the sensible weather here in the Northeast. With the mean trough axis shifting west and ridging taking hold in the east, a marked warm-up should ensue as next week begins. Forecaster confidence was much higher regarding an extended period of warmth in the long term that would take us right up into around the solstice but this confidence has since waned some. A very active northern branch in recent weeks gives me pause as to how much the warmth will be able to sustain itself over the region. Despite teleconnections being less than ideal for cold air intrusions punching into the Northeast feeling here is that models have been too aggressive in amplifying the pattern over North America as of late and, perhaps, the flow will be more zonal than meridional, allowing for backdoor cold fronts to temper the warmth. This is not to say that there won’t be any mild stretch of weather because there will be several days where winter goes on vacation. However, as mentioned in my seasonal outlook, the ridge forecast to develop over Eastern North America may find itself flattened at its crest, leaving the door open for cold air to sneak down into the region. Time will tell the story but for snow-lovers the suicide watch will be put on hold for now until the situation becomes clear. There’s still hope for a white Christmas after all.


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Radar: Northeast Region Loop

NE radar

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Current snowcover

Northeast Snowcover


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Local SST's

Northeast SST's

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Ferndale, NY climagraph



*averages used are from WU Monticello data minus one degree on highs and lows to better represent my local region. Actual temperatures are from my PWS.
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2008-09 Winter Forecast

Updated: 10:28 PM GMT on December 10, 2008

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Storminess on the horizon

By: sullivanweather, 11:33 AM GMT on December 06, 2008

Current watches, warnings and advisories.


Eastern US current watches/warnings

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Forecast Discussion


Synopsis - Issued 12/06 @6:30am


A clipper system races through the Northeast this weekend with most locales getting at least some snowfall. The coldest airmass of the season follows in its wake but will be transient in nature, with temperatures aloft warming by Monday PM. For midweek and beyond a very complex synoptic pattern develops over the eastern half of the country that will send at least one wave of low pressure across the region and perhaps a coastal low to close out the week.


Short-term - Issued 12/06 @6:30am



Mid and high level clouds are already on the increase early this Saturday morning across the western portion of the region in advance of an approaching Alberta clipper. This fairly potent system is moisture-starved and will be moving into a rather dry airmass currently over the region. Flow ahead of this system is also helping to push lake effect bands northward, as winds turn southwesterly. Communities north of Buffalo and along the St.Lawrence River Valley may see a few inches of fluffy snowfall this morning before activity tapers off as wind gains more southerly component. By this afternoon synoptic snow showers associated with the clipper will make their way into western New York and Pennsylvania as clouds spread over the remainder of the region. With clouds moving in and a rather low subsidence inversion limiting mixing temperatures will struggle into the 20’s across the interior and into the 30’s along the coastal plain. Winds will increase from the south around 10-15mph across the west while light and variable winds in the east become southerly around 5-10mph during the afternoon.

Snow showers increase in coverage this evening into the overnight as low pressure moves to the Niagara Frontier from Michigan. On piece of shortwave energy within the overall trough will spawn a secondary area of low pressure off the Carolina Coast that will rocket off the coast, sparing the region a significant snowfall. As energy is transferred to the secondary area of low pressure the primary low over western New York will weaken, however, a weak surface trough axis that develops between the two areas of low pressure will provide enough convergence across the region for scattered snow shower activity. Any accumulations will be light, basically a coating to an inch or so with a few exceptions. Aid from orographic lift may provide up to 3-5” of snow across the southwest facing slopes of the Adirondacks, Green and White Mountains of northern New York and New England. Also, as low pressure moves east and winds turn to the northwest, the lakes will become involved with 3-5” of snowfall also expected across the snowbelts just downwind of Lake Erie and across the Allegheny Front. Snow:liquid ratios will be very high, almost 20:1, which should help these amounts be realized despite the fairly dry airmass in place. Onshore flow over Maine will also help to get a limited level of Atlantic moisture involved, with perhaps 2-4” of snowfall expected from the central Maine coast to the border with Nova Scotia. Clouds will keep temperatures from freefalling after sunset and lows will likely fall into the teens across the interior with 20’s along the coastal plain and low 30’s along the immediate coast.

As the main shortwave within the 500mb trough pulls offshore Sunday it will greatly invigorate the secondary low pressure, causing it to develop rapidly. Unfortunately for snow lovers, this will occur too far offshore for any widespread meaningful snowfall across the region. Instead, a couple small areas will need to be watched for any mesoscale areas of enhancement. Namely along the southeast coast of New England, including Cape Cod, where a norlun trough-like feature could wring out a couple inches. As always, with a very cold arctic airmass invading the region, the lakes will become a hotbed of activity with numerous snow showers developing downwind. Northwesterly flow will promote a multi-band event and tend to keep accumulations down. In addition, the cold dry airmass following the clipper and low inversions will also cut back on a major event, despite deltaT’s ranging from 24-28°C. As the low pressure offshore rapidly deepens and strong cold air advection ensues behind the cold front winds will become quite strong and gusty. Winds will range from 15-25mph with gusts as high as 40mph. Areas with fresh snowcover will see lots of blowing and drifting and wind chills will drop below zero across the interior by afternoon (single digits and low teens along the coast). High temperatures for the day will likely be reached before the noon hour with falling temperatures during the afternoon. Across the interior temperatures should begin the day in the mid to upper 20’s, falling into the lower 20’s and teens by mid to late afternoon. Along the coastal plain temperatures in the 30’s will hold steady for much of the day and fall back into the upper 20’s before sunset.

Sunday night is likely to be the coldest night of the season as 850mb temperatures fall from –12 to –20°C across the region. Strong winds, along with wrap-around/upslope snow showers across northern New England will make for a very nasty night to be venturing about. Here temperatures will dive into the teens and single digits with wind chill readings approaching 20 below across the higher terrain. North facing slopes will see an inch or two of snow accumulation that will be blown about by those strong winds. Across New York and Pennsylvania high pressure will quickly build into the region. Lake effect snow showers will continue but dramatically decrease in coverage as the inversion comes crashing down after midnight. Skies will clear and winds will slacken, allowing for better radiational cooling conditions as the night wears on. A few locales may fully decouple a few hours before daybreak resulting in some very cold low temperatures. I would not be surprised to see a below zero reading or two reported in northwest Pennsylvania with single digits and low teens expected elsewhere away from the immediate lake shores where the moderating influence of those large bodies of water hold temperatures in the upper teens. Along the coastal plain temperatures may also spend their first night in the teens, although the urban centers and along the immediate coastline lows should stay in the low 20’s.


Snow from clipper/lake effect





Mid/long-term - Issued 12/06 @6:30am


Monday begins very cold across the entire region as arctic high pressure slides across the Mason-Dixon line and offshore by afternoon. Snow showers still ongoing across upslope regions of northern New England will end by noon as low pressure moves to the Labrador Coast. A shearing shortwave trough will rapidly spread mid/high level clouds across the southern half of the region late in the morning, making for a mostly cloudy day and masking the sun on a day it’s needed badly. Skywatchers may be interested, however, as high thin crystalline clouds usually bring sun dogs, pillars, and other atmospheric visuals. Temperatures should hover 10-20 degrees below normal region-wide.

Great uncertainty remains in the mid/long term section of the forecast. As always, models are having great difficulty attempting to decipher the phasing of northern and southern stream systems anticipated to occur somewhere over the Plains/Mississippi Valley region of the country as the week begins. Where and when this occurs still has big implications here in the Northeast. One wave of low pressure should develop and move northeastwards, spreading precipitation into the region on Tuesday. Across the interior of New York and Pennsylvania, snow should develop, gradually mixing with sleet and freezing rain across the southern half of this region by afternoon as warm air moves in aloft. Along the coast, precipitation will start as snow and gradually mix with sleet and freezing rain, eventually becoming rain by the afternoon as the boundary layer warms above freezing. Depending on the level of phasing and ensuing track of low pressure will determine further changes in precip-type Tuesday night, although there should be additional northward movement of the transition zone. Cold front blows through on Wednesday with arctic air moving back in and lingering precipitation changing over to snow. QPF from this wave should range from a half inch to an inch and a quarter, so should most of this fall as snow and/or ice, it could get quite messy.

Thursday and beyond still remain a mystery as some models develop a lingering southern stream disturbance into a Miller type-A coastal system while other model runs show a system sheared from the main flow and passing harmlessly over Florida then out to sea and everything in between. One thing that is agreed upon is that it will be cold, with temperatures some 5-10 degrees below normal. Stay tuned for updates on the potential storm late next week.


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Radar: Northeast Region Loop

NE radar

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Current snowcover

Northeast Snowcover


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Local SST's

Northeast SST's

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2008-09 Winter Forecast

Updated: 1:01 PM GMT on December 06, 2008

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Cold, cold and more cold

By: sullivanweather, 8:38 PM GMT on December 03, 2008

Current watches, warnings and advisories.


Eastern US current watches/warnings

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Forecast Discussion


Synopsis - Issued 12/03 @3:30pm


A sharp cold front with anafront characteristics will move through the Northeast Thursday, delivering an icy blast of arctic air that will remain entrenched over the region until early next week. Lake effect snow will follow in its wake, which could be quite a significant event in the snowbelts. High pressure builds in to begin the weekend but will quickly give way to a clipper to close out the weekend that may undergo coastal redevelopment, bringing an accumulating snowfall to Maine.


Short-term - Issued 12/03 @3:30pm


Mainly clear skies will begin the night but clouds will increase as the night wears on as warm air advection ensues behind the departing high in southerly flow. However, enough clear skies and a decoupling of the winds after dusk should make for ideal radiational cooling conditions for a couple hours, especially across the eastern portion of the region. The cold front will punch into western New York and Pennsylvania after midnight, accompanied by rain showers that will quickly change to snow as colder air filters in aloft. A coating to an inch or two of snow may fall behind the front, which is a nuisance snowfall for Northeasterners, but what lies beneath is where there will be trouble. The initial liquid precip followed by a rapid cooling may result in a flash freeze of road surfaces. Anyone traveling across the western half of the region will have to keep this in mind. Temperatures tonight will drop sharply after sundown before leveling off, or even rising a couple degrees, once the cloud deck moves in. Across western sections, temperatures will drop once again after the frontal passage, so a rather atypical temperature profile across the region tonight. Lows will fall into the 20’s across the interior with 30’s along the coastal plain and across the far western sections of the region where clouds will move in quickly after sunset. Winds will be light and variable but increase to around 10mph out of the south just ahead of the front and turn towards the west after its passage.

The cold front continues to march across the Northeast during the day on Thursday, with much of the associated precipitation falling behind it. QPF with this feature will be light, mainly a tenth to a quarter inch. Ahead of the front, temperatures in the boundary layer should warm sufficiently to allow for rain showers to fall initially, but rapidly cooling air thanks to strong cold air advection behind the front and dynamic cooling of the column will make for a quick transition to snow across the interior. Along the coastal plain this changeover will likely take much longer to occur, if at all. Elevations above 1,000’ could see a fast inch or two of snow accumulation while at lower elevations any accumulations will likely be confined to colder surfaces, such as grassy areas or car tops. Lake effect activity will also develop by afternoon as increasing deltaT’s create enough lake induced instability for snow showers. Once again, temperatures will follow an atypical diurnal trend. Across the western half of the region, where the frontal passage will occur during the overnight/early morning hours, temperatures will slowly fall during the day from the 30’s into the 20’s by mid afternoon. Meanwhile, areas that see the frontal passage occur during the late morning/early afternoon will see a fast rise in temperatures into the upper 30’s to low 40’s, then after the frontal passage a slow fall back into the low to mid 30’s. Along the immediate coastal plain temperatures should easily climb into the upper 40’s as the front won’t reach these areas until late in the afternoon. Southerly winds of 10-15mph ahead of the front will quickly turn to the west behind it and become quite gusty in strong cold air advection.

The cold front will be off the coast by this evening will any lingering precipitation along the coastal plain transitioning over the snow showers. Lake effect snows will increase as 850mb temperatures drop to nearly –15°C in/around the Great Lakes region, increasing deltaT’s to ~20-22°C. Despite the extreme lake induced instabilities and rather high inversion levels, there will be some deterring factors to seeing a substantial event. For one, the flow won’t be well aligned and will likely oscillate between 270-290°, which won’t keep the bands over any one particular area for any significant length of time. There’s also likely to be about 20-30° of directional shear in the 1000-700mb flow that should spread the band out and synoptic moisture will be lacking. Regardless of these deterrents, snowfall across the Tug Hill Plateau, western Adirondacks and across some of the higher terrain of Northwest Pennsylvania to the region surrounding Jamestown, NY could easily see 6-12” of lake effect snow overnight. Lighter amounts will fall in the immediate surrounding regions. Lows will fall back into the teens across the interior with 20’s along the coastal plain. Winds will be out of the west around 10-15mph.


Mid-term - Issued 12/03 @3:30pm


Cold air continues to bleed into the Northeast on Friday, keeping temperatures well below normal while lake effect snows continue across upstate New York. The flow will turn to more of a west-southwesterly direction as the day progresses as high pressure slides by to the south over the Mid-Atlantic. Inversion levels will also lower, making for lighter lake snows as the bands progress to the north, reaching the Buffalo/Watertown areas. Elsewhere skies will be partly to mostly sunny as temperatures remain in the 20’s across the interior, with 30’s along the coastal plain.

The next system of concern will be a potent clipper system dropping into the deep trough carved out over the eastern half of the nation this weekend. Being from the northern branch, this system will be moisture-starved, but will carry with it some rather impressive dynamics that should be able to squeeze out whatever available moisture presented to it. Hence, a widespread snow shower event is expected to spread over the entire region. As the trough reaches the coast it should begin to take on a negative tilt with a secondary surface low pressure developing offshore. Models are currently hinting at the possibility of a norlun trough developing between the offshore low and the parent low hanging back over the US/Canadian border region. A surface trough axis in the pressure field is apparent, as well as a thermal ridge axis. As Atlantic moisture is tapped an accumulating snowfall may develop across coastal New England, especially Downeast Maine. Lots of time to sort out the details here but the weekend may be a snowy one from Cape Cod to Eastport, Maine, including the greater Boston area. The lake effect machine will also fire up behind the departing clipper in a strong northwest flow. Temperatures will continue to average well below normal for early December.


Long-term - Issued 12/03 @3:30pm


High pressure quickly builds in on Monday, ending the lake effect snowfall. It will remain cold, however, with 850mb temperatures progged to range from –7°C to –15°C from south to north. Complications arise by midweek as an attempt of northern/southern stream phasing occurs in/around the Ohio Valley region of the country. Earlier model prognostications had a much more phased/amplified pattern developing across the eastern half of the country, which allowed warm air to flood up the coast bringing a rain event to much of the Northeast with a mix or snow confined to the far northwestern sections of the region. Ensuing model runs now show the possibility of the northern stream system outrunning the southern stream disturbance, for a time, before they catch up to one another. This would bring a sharp cold front into the Northeast where it will become hung up as both branches of the jet phase at a further east longitude. The result would be a much more wintry scenario to the region and a much more complicated forecast. Skipping on the details and focusing on the generalities, it appears as a significant QPF event is likely during the middle of next week with a very tight baroclinic zone setting up north-south across the region. The warm side of the storm could see flooding rainfall while the cold side of the system could see substantial snow/ice accumulations. More on this in the days to follow but be prepared to the possibility of a high impact weather event developing next week that could have widespread effects.


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Radar: Northeast Region Loop

NE radar

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Current snowcover

Northeast Snowcover


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Local SST's

Northeast SST's

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2008-09 Winter Forecast

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About sullivanweather

Thomas is an avid weather enthusiast, landscaper and organic gardener. This blog is dedicated to Northeast and tropical weather forecasting. Enjoy!

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