Northeast Weather Blog

The one that got away?

By: sullivanweather, 10:18 AM GMT on January 31, 2009

Current watches, warnings and advisories.


Eastern US current watches/warnings

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Forecast Discussion


Synopsis - Issued - 1/31/09 @5:15am


An upper trough axis responsible for scattered snow showers and squalls on Friday will be moving offshore today with lake effect snow left in its wake. Northern stream remains active on Sunday with more snow showers for the North Country. The big story during the forecast period will be the near miss. After toying with the notion of a potential nor’easter models have bucked their recent trends as well as the seasonal westward trend now showing the track of a southern stream low far enough offshore to spare a significant winter storm to the region aside from the lone but steadfast GFS. Instead, light to moderate snow can be expected along the Eastern Seaboard with the best chances for higher accumulations over Cape Cod and Downeast Maine. Arctic air drains south from Canada after the storm’s passage with an active northern branch sending a clipper towards the region by Thursday.


Short-term - Issued - 1/31/09 @5:15am


Lake effect snow will be found across upstate New York today in a northwesterly flow during the morning hours that will gradually shift towards the west by afternoon. DeltaT’s are around 18-20°C and inversions are just below 750mb. However, the flow is slightly sheared which is preventing some organization of the bands and spreading the wealth. Accumulations through noon should range from 2-4” in favored areas southeast of Lake Ontario with 2” or less outside of this area. As the flow backs and bands lift north during the afternoon the Tug Hill Region will get in on the lake effect with 2-4” there and up to 2” extending to the western Adirondacks. There’s a slight window during the early afternoon where the bands may become slightly more organized but with lowering inversions and anti-cyclonic flow developing, the lake effect should wind down by evening. Not much going off Lake Erie as that lake has now almost completely frozen over. Some latent heat is providing conditional instability and up to an inch of snow may fall in one or two bands that manage to organize but this will be a short-lived event as the marginally favorable conditions cease by mid-morning. Elsewhere across the Northeast scattered snow showers can be found across upslope regions of northern New England and perhaps along the coastal sections of Downeast Maine as an oceanic storm scoots by to the east. This storm had shown some promise in the models of turning up the coast at the beginning of the week but the upper trough axis currently moving through the Northeast was late in arriving. Elsewhere skies will be partly to mostly cloudy as convective temps should be reached allowing for cumulus/stratocumulus development by late morning. High clouds will also increase from the west during the afternoon as warm advection commences ahead of the next disturbance. Highs will range from the mid to upper 20’s along the coastal plain with lower 20’s and teens inland. Across the higher terrain temperatures should remain in the single digits.

Surface low pressure north of the Great Lakes will send a warm front towards the Northeast tonight with increasing clouds and snow showers developing in weak isentropic lift from the Allegheny Front to the Niagara Frontier. These snow showers may leave a coating to perhaps an inch. Further east clouds will be later in arriving allowing for temperatures to fall slightly after dusk before holding or perhaps rising toward morning as clouds move in and temperatures aloft warm by some 6-7°C overnight. The coldest temperatures tonight will be found across Maine where, once again, overnight lows will fall below zero across the Allagash. Elsewhere across the region temperatures will manage to remain above the zero mark with lows in the single digits over the remainder of the North Country. Teens will be found elsewhere across the interior with 20’s along the coastal plain.

Clouds and snow showers remain over the interior on Superbowl Sunday as low pressure moves into southern Quebec. Temperatures will be close to seasonal averages or a few degree over with highs in the 20’s across the northern interior and 30’s across the south and low 40’s along the coastal plain. More of the same Sunday night as clouds persist. Lows will be 5-10 degrees above normal.


Mid-term - Issued - 1/31/09 @5:15am


Big questions remain in the midterm (Monday-Wednesday) but the trends are becoming a bit more clear. The much hyped up potential for a major coastal storm is starting to wane as models have shifted the track of this storm east over the waters of the western Atlantic. As discussed in the previous blog there was a plethora of conditions that needed to come together correctly for this storm to materialize and recent model trends have moved away from a coastal solution for a variety of reasons. First and foremost is the northern stream trough’s position and orientation. Progressive nature of this trough and positive tilt exhibited in the models fails to capture the southern stream low forming in the Gulf. In addition a second, stronger shortwave diving down the backside of the trough that would have phased with the Gulf low will be a hair late in arriving. This means cyclogenesis should occur just far enough offshore to clip the coastal sections with precipitation. However, given the poor handling of this storm throughout recent days I’m not willing to completely close the book on this one yet. The lone model still showing a major East Coast snowstorm continues to be the very consistent GFS. This was the first model to pick up on this storm and is still the only model in the boat as the others have already jumped ship. The GGEM/ECMWF/UKMET all take this storm too far east of the region for a widespread significant snowfall though Cape Cod and Downeast Maine still stand a chance at seeing something a bit larger. Regardless of a blockbuster storm or not, light snow should still develop should a full-fledged storm not develop. This will be along a surface trough lingering along the coast as moisture streams north and frontogenesis develops. The western portions of the region should escape the wrath of this storm and see only scattered snow showers in association with the upper trough axis, cyclonic flow and some lake enhancement. A much colder airmass will also dive south from Canada with temperatures starting the period near normal to slightly above on Monday before falling back below seasonal levels by Wednesday.


Long-term - Issued - 1/31/09 @5:15am


Another northern stream trough approaches in deep-layer northwest flow on Thursday bringing more snow showers to the region. By Friday in next weekend a moderating trend should finally ensue as a pattern change may be in the offing as troughing develops over the west with building heights in the east. Over the last 3 weeks models have been showing moderating temperatures in the day 7-10 period but thus far these have failed to materialize. Will be keeping an eye on latest model trends to see if this is a phantom warm-up or the real thing.



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Updated: 10:20 AM GMT on January 31, 2009

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Nor'easter possible next week

By: sullivanweather, 11:59 AM GMT on January 29, 2009

Current watches, warnings and advisories.


Eastern US current watches/warnings

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Forecast Discussion


Synopsis - Issued - 1/29/09 @7:00am


Yesterday’s winter storm has rapidly moved into the Canadian Maritimes becoming a powerful extra-tropical cyclone, lashing that region of Canada with heavy snow and high winds. Left in the wake of this storm are blustery winds and lake effect snow showers across the snowbelts. The passage of several shortwaves rounding the base of an upper level trough will keep clouds and snow showers around the Great Lakes and Northeast into Saturday. Another northern stream disturbance moves into the Northeast on Sunday evening that will have big implications on the potential for a major winter storm come early next week. Low pressure will form in the Gulf of Mexico and track along a stationary boundary trailing from Sunday evening’s system so how far east this front progresses will determine who sees rain and who sees snow. Much below normal temperatures plunges into the Northeast following the system for midweek.


Short-term - Issued - 1/29/09 @7:00am



For those following the scoreboard this winter season it’s Euro: 12, GFS: 1. Once again after a seemingly set-in-stone snowfall for many just a couple days out in time, numerical models, led by the ECMWF’s charge, gradually pulled the storm to a more northerly course that ultimately ended in a messy mixture of frozen precipitation types for a large portion of the Northeast. This right of track bias has been a persistent theme this winter nearly every winter storm to affect the region. The question now is what track will verify for a potential major nor’easter early next week? More on that later. Currently, cold, moist cyclonic flow lingers over the Northeast this morning as yesterday’s winter storm moves away. This has induced lake effect/upslope snow showers over the interior while coastal locales see mainly cloudy skies. Flow this early morning is around 290° but this should gradually shift to a more southwesterly trajectory as we progress into the afternoon as a trough slides in from the west, lifting snow showers to the north. Low-level profiles suggest a bit of shear, spreading the snow out with little organization shown on radar loops. A general 1-4” of snow can be expected today from this lake effect, with the highest amount centered in the Tug Hill Plateau region and the western Adirondacks. Elsewhere across the region skies will be mostly cloudy with a few scattered morning flurries. A bit of downsloping will break the cloud cover over the coastal plain where partly sunny skies will be the rule. Continued cold air advection will also make for quite blustery conditions today. Diurnal influences will allow for a fairly well mixed boundary layer where a 20-30kt flow will be present. 850mb temps fall to –6°C to –14°C across the region leading to highs in the low 30’s along the coast with teens and 20’s over the interior. Winds will be from the west at 10-20mph with gusts to 30mph.

A weak surface trough along with a couple H5 shortwave disturbances slide through the Northeast tonight through Friday night. Clouds will increase once again as will the coverage of snow showers, mainly found across the interior. 850mb temps continue to drop as well, increasing lake induced instability as deltaT’s approach 20°C. Lake enhancement will lead to accumulating snows of 3-8 inches in the favored snowbelts on a 270-290° flow. Accumulating snow will also be found along the Allegheny front and the Laurel Highlands where upslope flow may deposit 2-4 inches of fresh snowfall. Just a reminder that Lake Erie is almost completely frozen over now lessening the effectiveness for this lake to produce snow across western Pennsylvania and New York. Diurnal influences will also increase lapse rates allowing for numerous snow showers away from the lakes, however, with little accumulation. Along the coastal plain a few snow showers may survive the trip down the mountains and mostly cloudy skies will do. Temperatures will drop to near normal levels during the overnight periods due to the coverage of clouds and remain several degrees below normal on Friday.


Mid-term - Issued - 1/29/09 @7:00am


The upper trough begins to pull offshore on Saturday but another shortwave diving down the backside of this trough will lead to more snow showers scattered about the region. Flow turns northwesterly behind the trough axis as well igniting lake effect/enhanced snows across central New York and northeast Pennsylvania and orographic snow showers over the mountainous terrain over northern New York and New England. One small caveat to watch for will be the development of low pressure over the western Atlantic that may come close enough to Downeast Maine to provide that region with a couple inches of snow. This would be due to an inverted trough that models are currently trying to resolve developing on the western side of this low. Otherwise, continued cold and blustery conditions for the Northeast as the cold core of the modified arctic airmass sits squarely over the region. Temperatures will be around 5-10 degrees below normal.

Northern stream becomes more zonal through the second half of the weekend with warm air advection increasing. Weak low pressure will move to a position north of the Great Lakes with the flow turning more to the southwest over the region. Warm frontal frontogenesis occurs Saturday night and Sunday that will once again spread clouds and snow/rain showers over the region. Temperatures will moderate as well, with 850mb temps climbing roughly 8-10°C from their Saturday readings. 0°C isotherm rides north to the NY/PA border region which will be the dividing line to snow north and rain south. QPF is on the light side with just a couple hundredths of an inch expected so nothing more than a ground wetting/coating expected.


Long-term - Issued - 1/29/09 @7:00am


Main forecasting challenge awaits in the long-term. Very complicated situation setting up as a classic Miller type-A development occurs in the Gulf of Mexico this period. Major model differences are already apparent with a clustering of models showing the movement of this low pressure up the Eastern Seaboard. A second clustering of models have the storm moving up the Appalachians, including the dreaded ECMWF solution. The differences lie in the models respective handling of the northern stream pattern, which has two disturbances in question. The first is the low pressure discussed in the mid-term period over Ontario. This low will drop a trough across the Northeast that will ultimately become the baroclinic zone in which the Gulf of Mexico low will travel up. The second shortwave will be screaming southeastward out of Canada that will sharpen the longwave trough over the eastern US and energize the Gulf low as it lifts north. Since there are so many factors that will influence the track of this low I’ll lay them out to illustrate the complexity of this upcoming storm.

Upstream blocking – The NAO will be taking a strong dive towards negative territory during the beginning of February. This will allow for building heights over the Northwest Atlantic, effectively stopping the eastward progression of any disturbances approaching from the west. Problem is that as cyclogenesis occurs over the Gulf, the blocking ridge will be to the storm’s east and not the storm’s north. This factor argues for a western low track.

Residual airmass – As the storm approaches, the airmass over the Northeast won’t be particularly cold. The frontal boundary moving into the region is of Pacific origin with maritime polar air behind it. This airmass will also have with it the residual effects of a moderate Chinook. Not usually an ingredient for a major snowstorm.

Right of track bias in the models – Just about all winter long as models got a better grip on the situation at hand a gradual shift to the west/north occurred. Of course, this is nothing more than a non-scientific observation of model trends but being that the model taking the lead in picking out the west/north trends of approaching storms has been the ECMWF model. And this model was the first one to show the Appalachian track. Again, argues for the western track to the low

Antedecent conditions – Snow/icepack now extends far to the south over the eastern states, in some cases a very deep snowpack. Will this temper the Chinook warmth as it heads east over the snowpack bringing the baroclinic zone closer to the coast? If so, then a track to the east may be more plausible and the residual airmass over the Northeast may be just cold enough for a snowier scenario (it will be February, afterall).

Resolving the northern stream ‘phaser’ – This disturbance is still over Asia. Timing this shortwave as it drops into the longwave trough is nearly impossible this far out in time. There’s still a chance that this disturbance doesn’t even phase up with the southern stream Gulf low until it’s halfway to Bermuda. There’s also a chance that it phases to early the storm pulls into the Ohio Valley. Although the spread is much more narrow in the models any track between the above two mentioned areas is still possible.

Where’s the front? – The lead shortwave in the northern stream will have a front draped over the Northeast attached to it. This weak front will eventually become a strong baroclinic zone that the low pressure will track along. The upstream blocking will have a say in how far eastward this front will be able to progress so the building heights over the western Atlantic will need to be watched closely as it closely ties into the position of this front.

Low track – Regardless of which route it takes the direction this low will travel in is almost due north, perhaps backing if/when 700/500mb lows close off. This will allow for warm air to flood up the eastern flanks of the storm while cold air holds nearly in place along the western flanks. As mentioned above, the residual airmass over the region is of Pacific origin and won’t be particularly cold so a clear-cut rain/snow line in a south-north axis should exist with little in the way of sleet/freezing rain.


There you have it. Basically, any solution is still possible at this time. In terms of sensible weather, the eastern side of this storm will be very mild Atlantic air flood into the region with copious amounts of rain, easily over an inch. This would likely create flooding problems due to the amount of QPF combined with melting snow, which may melt rapidly with rain/mild temps/high dewpoints/strong winds. With the recent stretch of very cold air rivers are likely frozen over presenting the probability of ice jams. Along the western side of the storm blizzard conditions will be possible. Snow will be very heavy with strong winds as the low bombs out into the 970mb’s. Precip from the storm will move into the southern portion of the region Monday afternoon, spreading into New England by Tuesday morning. The storm pulls into Canada on Wednesday with numerous snow showers in its wake and much below normal temperatures as it drags an arctic airmass into the region.


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Updated: 5:27 PM GMT on January 29, 2009

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Significant winter storm to impact the Northeast

By: sullivanweather, 9:45 AM GMT on January 27, 2009

Current watches, warnings and advisories.


Eastern US current watches/warnings

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Forecast Discussion


Synopsis - Issued - 1/27/09 @4:45am


A major winter storm will move through the Northeast over the next 48 hours providing up to a foot of snow across the interior and a messy mix along the coastal plain with up to ½” of ice on top of significant accumulations of snow. Clouds and snow showers linger Thursday and Friday as the upper trough pulls through with gradually improving conditions by the weekend. Temperatures will remain near seasonable levels.


Near/short-term - Issued - 1/27/09 @4:45am


The proverbial calm before the storm has settled in over the Northeast this overnight. Only a few flurries are falling across central New York and northern Pennsylvania as a weak mid-level disturbance runs out ahead of the main low pressure complex over the Mississippi-Valley. A shield of cold high cloud tops have also spread across Pennsylvania along the northeastern flanks of a developing baroclinic leaf seen on satellite imagery. The remainder of the Northeast has been mostly clear with calm winds thanks to a 1032mb high pressure centered over upstate New York allowing for ideal radiational cooling. Presque Isle, Maine sits at –26°F at the time of this writing, a very cold night but not nearly as cold as the –30’s and –40’s there last night!

Clouds will continue to slowly spread over the region today ahead of the organizing low pressure over the Mid South. A few snow showers or flurries may skirt along southern Pennsylvania but these should mainly stay south of the Mason-Dixon line through the afternoon thanks to confluent flow and subsidence. Other than another small area of minor lake effect snow around the Tug Hill Plateau much of the day will be spent precipitation-free allowing for any preparations to be made before the storm hits. Temperatures will recover nicely from their bitter morning lows as the arctic airmass that has been entrenched over the Northeast modifies. Highs will reach the 20’s to low 30’s across the southern half of the region with teens hanging tough across the north. A few single digits cannot be ruled out over the higher terrain of northern New York and New England. Winds will be light and variable but will start to increase out of the east across the southern half of the region later in the afternoon.

It all starts going downhill tonight as the surface low pressure pulls into the Tennessee Valley. Increasing low-level jet our ahead of the low will help to transport higher theta-e air over a tightening baroclinic zone just south of the Mason-Dixon line. Isentropic lift will increase and snow will break out from southwest to northeast across Pennsylvania and New Jersey, reaching the NY/PA border by midnight. Snow will become rather intense at the nose of a 50-60kt low level jet punching into southern Pennsylvania with strong UVM noted in the mid-levels (-15microbars/sec omega) and west-east frontogenesis over the northern half of the state. Snowfall rates should approach an inch an hour in these bands so it will add up quickly. After midnight this strong forcing moves into New York state and adjacent western New England while warmer air streams north on aforementioned 50-60kt low-level jet. 0°C isotherm @850mb punches into southern Pennsylvania and southern New Jersey by daybreak changing precipitation over to a mixture of sleet and freezing rain. Thickness profiles indicate this warm layer is from 875mb to 750mb in the atmosphere pointing to more sleet at the onset of the transition as opposed to freezing rain. Accumulations during the overnight period will be light to moderate, ranging from 3-5” across northern Pennsylvania and 2-4” across southern Pennsylvania, where precip changes over. Further north over New York and western New England accumulations will range from 2-5” with the higher amounts to the south where the snow started earlier. Over far northern New York and central/northern New England there will be increasing clouds but the snow should hold off until Wednesday. Overnight lows will range from the 20’s across the southern interior and coastal plain to the teens north of the I-80 corridor into northern sections where a thinner cloud cover and light winds will allow for some level of radiational cooling. Here one can expect lows in the single digits above/below zero.

Complexity rises on Wednesday as models are still having some timing/track issues with the surface low and its respective lows aloft. There’s basically two camps in the models right now with the Euro (ECMWF) model showing a low track much further north than the GFS/NAM/GGEM/SREF suite of models. The Euro takes low pressure across the coastal plain about 50 miles inland with the 850/700mb lows tracking close to the Canadian border. The remainder of the models show low pressure tracking further south to varying degrees with coastal reformation around the Long Island area. This secondary low then tracks northeast along the coast into the Gulf of Maine by Wednesday evening. The models that show the southern solutions also show the track of the 850/700mb low couplet across central New York and New England. Obviously the implications of a ECMWF track would be for a much greater degree of mixing and the heaviest snows to fall over northern New York and New England along the tracks of the 850/700mb lows in the comma head/deformation band expected to develop as the storm wraps up over southern New England. The GFS/NAM/SREF/GGEM would have less mixing across the interior and the heaviest snow tracking from north-central Pennsylvania across east-central New York and across southern Vermont, southern New Hampshire, northern Massachusetts and southern/Downeast Maine. Using a blend of these differing solutions appears to be the best way to go at this time, more weighted towards the southerly solutions. The ECMWF, having been good at sniffing out the northerly tracks of low pressure this winter does raise concern. Also the American models have typically underestimated the northerly push of warmer mid-level air this winter. However, in previous events there was more shortwave ridging in the mid-levels ahead of similar systems, fleeting surface high pressure and a much milder airmass in place as the storm approached. This time, there’s a lingering modified arctic airmass, but one that was very chilly to begin with, so there’s plenty of deep cold air left over the region. The flow aloft is quite flat and fast with very little ridging in mid-levels ahead of the system. And the surface high pressure over New England of 1032mb should hold on long enough to deflect the low southward to some degree. Obviously, there’s factors that point towards the southern solution but the Euro’s superior handling of the strength of the H5 shortwaves this winter merit the consideration in that model’s projected northern track.

Things to watch for tomorrow include: 1) the development of any coastal front that would help to induce secondary cyclogenesis further south than the Euro solution. 2) Tracks of 850/700/500mb lows as this will determine where the strongest frontogenesis fields line up. Current thinking is this happens over south-central New York into the northern Catskills, and north of the Mass Pike northeastward to Downeast Maine. This area looks primed to pick up to a foot of snow or more with rates of an inch to two inches an hour. 3) Northward progress of the above freezing air aloft. Models have poorly resolved this aspect in many prior storms this winter with the ECMWF model having the best success with this. For this storm the ECMWF model pushes the 850mb 0°C isotherm to Albany, NY and across southern Vermont and New Hampshire. This would significantly cut down on snow totals between the I-90 and I-80 corridors with more ice falling and rain eventually for the coast. These three aspects of the storm will have big implications on the snow/ice forecast. Still much uncertainly in precip type.

In terms of sensible weather, snow will fall over much of the interior during the day on Wednesday north of the I-80 corridor (I-84 New York/New England). To the south snow will change over to sleet, which could last several hours, then freezing rain. Significant accumulations of ice may also occur in areas south of I-80 to within 25 miles of the coast (10mi New England) where boundary layer warms enough to slow the accretion rate of the ice or for completely liquid precip. As the secondary low pressure eventually takes over around the Cape Cod region, winds turn back from the north, heights crash and 850’s fall rapidly. Lingering mixed precipitation turns to snow right down to the coast with very heavy snow moving into central/northern New England by late afternoon/evening. Low rapidly intensifies to a 985mb low pressure over Nova Scotia as a deformation axis of heavy snow hammers northern New England during the overnight. Total snow/ice accumulations will be detailed in the map. Lingering snow showers will extend back into New York State with lake effect/enhanced snows developing southeast of Lake Ontario in cold moist cyclonic flow. Temperatures on Wednesday warm into the mid 30’s along the immediate coast and southern New Jersey/extreme southeast Pennsylvania. Just inland of the coast temperatures will climb to around freezing with below freezing temperatures throughout the interior; teens and 20’s. As cold air floods back into the coastal plain tonight flash freezing will be a concern as temperatures rapidly fall back into the 20’s. Across the interior lows will bottom out in the teens. With the low pressure rapidly intensifying overnight Wednesday winds will get blustery, more so in New England closer to the storm center.

*Updated - 1/28/09 @4:45am



Mid-term - Issued - 1/27/09 @4:45am


Lake effect snow combined with a minor shortwave will keep snow showers in/around the eastern Great Lakes on Thursday. Trowal will still extend over northern New England from the departing storm. This and cyclonic/upslope flow should produce snow showers over the higher terrain of this region. Elsewhere it will be partly to mostly cloudy and most will be digging or chipping out. Highs will be seasonably cold, around normal to 5 degrees below. Clouds and snow showers remains scattered about the Great Lakes region Thursday night with mostly cloudy skies elsewhere.

The upper trough pulls into the region on Friday and Saturday. Thus far it doesn’t appear as through this trough will sharpen up enough for a storm moving off the Southeast Coast to make the turn up the coast but this is still a slight probability. What’s most probable is the trough passes through with scattered snow showers but keeping in mind that the outside chance does exist for something bigger to come from this. For example, 2 days ago the storm due on the 27-28th was supposed to be a northern Mid-Atlantic storm and now it might be a northern New England storm. So a storm out to sea may still be a storm close enough. Just something to keep in the back of the mind while the current mess sorts itself out.


Long-term - Issued - 1/27/09 @4:45am


High pressure builds in to close out the weekend bringing a slight moderation in temperatures. Next week another trough approaches from the west with cold air returning behind it.





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Current snowcover

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Updated: 9:46 AM GMT on January 28, 2009

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An old-fashioned winter.

By: sullivanweather, 11:33 AM GMT on January 25, 2009


Current watches, warnings and advisories.


Eastern US current watches/warnings

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Forecast Discussion


Issued - 1/25/09 @6:30am

Who wanted an old fashioned winter? Over the next two days arctic high pressure will build over the Northeast, extending back across the northern tier of the country towards the Continental Divide. Meanwhile, stacked low pressure over the Great Basin will slowly rotate out of the Intermountain West and into the Plains. Gulf of Mexico will be open to this low pressure, feeding moisture into a tightening baroclinic zone extending from northern Oklahoma to the Mid-Atlantic. Low pressure will track along this zone, bringing wintry precip types, mostly snow, to the southern two-thirds of the region by Tuesday, lasting into Wednesday. Could be a band of impressive totals from this storm. Northern areas continue to endure night after night of below zero temperatures. Seasonably cold air remains entrenched over the Northeast to end the week as one storm clears out and we may yet have another storm to be dealing with.


A very cold start to the morning as temperatures have fallen below zero across a wide swath of the interior. Some of the readings at this early hour include, -24°F at Berlin, New Hampshire, -18°F at Saint Johnsbury, Vermont, -12°F at Glens Falls, New York and –6°F in my backyard. Cold air has even made it down to the big cities with Boston reporting 10°F, New York City at 14°F and Philadelphia down to 18°F. Also ongoing this morning is a band of heavy lake effect snows across the northern Tug Hill Plateau, western Adirondacks and the 10,000 Lakes region. There should be significant accumulations today with this band and totals have already amounted upwards of a foot.

Dry and cold conditions should prevail for much of the day across the Northeast with the notable exception being the aforementioned area of lake effect snow. There are two other areas that will be exceptions to the rule as well. The first across the far north where a spoke of energy aloft and a surface trough rounding the polar vortex will set off a few snow showers, mainly confined to the higher terrain where a couple of inches may accumulate. There is also a weakening mid/upper-level disturbance that will track in from the Midwest but dry low levels will mean this will limit its associated precipitation to flurries across Pennsylvania by the time it reaches the Northeast. A dusting may coat the ground in some places, likely along the Allegheny Front and/or the Laurel Highlands but with any snow falling from the mid-deck and steep boundary layer dewpoint depressions, it may be hard for these to reach the ground in the valleys. High/mid level clouds will be the most visible effect this disturbance will have over the Northeast, basically from I-90 south, where skies should gradually become mostly cloudy. Mostly sunny skies will grace southern Vermont, New Hampshire and northern Massachusetts to take an edge off the cold and clouds will increase across the far north as that energy rolls in around the polar vortex. Temperatures today will be well below normal as highs struggle to climb into the single digits across the north. The remainder of the interior should remain in the teens with 20’s along the coast.

Another very cold night tonight but not as cold across the southern half of the region due to the upper disturbance providing a canopy of clouds to cut down on the radiational cooling. The northern half of the region, however, will have very little cloud cover, which will allow for ideal radiational cooling. Here temperatures should drop into the negative teens and 20’s once again. Some of the normally colder locations across northwestern Maine may even fall into the negative 30’s or even touch –40°F, as what occurred last week! Single digits and teens should do under the cloud canopy across the south but should some breaks occur late, even here temperatures could fall below zero.

High pressure builds in on Monday with mainly clear skies under a strengthening subsidence inversion across the north. Cannot rule out a few squalls along the south shore of Lake Ontario but that looks to be it in terms of precipitation. To the south, mid and high-level clouds will continue to stream overhead thanks to an intensifying jet streak over the region carrying upper-level moisture away from the developing storm over the Southern Plains. High temperatures will range from the single digits north to the teens and 20’s south.


Monday night is when the trouble starts as increasing isentropic lift over southwestern Pennsylvania induces an area of light snow to break out. This will be the leading edge of a major winter storm that will affect the midweek period. Elsewhere across the region clouds will begin to slowly spread north and it will remain cold and dry aside from the lake effect coming off Lake Ontario. Low temperatures will once again fall below zero to the north, with single digits and teens south.

Snow fills in across Pennsylvania and New Jersey on Tuesday as confluent flow over southern New England and upstate New York holds off the northeastward progress of the first wave of precipitation. The snow could come down moderate at times with 2-4 inches possible across the southern half of Pennsylvania and southern New Jersey with an inch or two north of there to the I-80 corridor during the day. Low pressure lifts east-northeast from the Tennessee Valley Tuesday night with its upper support tracking across the Ohio Valley. These features will converge on the Northeast by Wednesday morning. Snow will spread northeastwards and increase in intensity as this occurs. Ratios could be on the 12-15:1 side and given expected QPF, there could be quite a dumping across Pennsylvania over to southern New England. Some mixing may occur along the coast but a solid winter storm for most of the region. Those left out would across the far north but they will have their own set of problems with the very cold temperatures continuing. Snow will end from west to east Wednesday and Wednesday night, though some models hold the system back until Thursday. This has been a fickle system to track and a change in track/intensity/timing still may occur but confidence is increasing in regard to a major snowstorm during the Tuesday-Thursday period.


In the long term there may be just one more system that may create a buzz for a bit. A rather significant buckling of the zonal flow across the country in response to a potent northern stream shortwave will occur. Cyclogenesis should occur in the baroclinic zone expected over the northern Gulf at that time. The question from there is does it move out to sea? Or does it come up the coast? Normally, the skepticism in the models in the long range is pretty high. But this winter, it just seems to want to snow. A good old-fashioned winter. So I’ll say the possibility is real and the chances for not one, but two snowstorms is there.



___________________________________________________________


Radar: Northeast Region Loop

NE radar

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Current snowcover

Northeast Snowcover


___________________________________________________________

Local SST's

Northeast SST's


___________________________________________________________

2008-09 Winter Forecast


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2008-09 winter forecast revisited

By: sullivanweather, 10:09 PM GMT on January 19, 2009

With the fairly benign weather pattern shaping up over the next 5 days I'm reposting the 2008-09 winter forecast made on November 4th. Mid/long term forecast from previous blog will be found under the seasonal forecast section. New blog will likely be posted Wednesday or Thursday detailing the possibility of a major nor'easter next week should this remain a possibility.

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A good phrase that may describe the upcoming winter season in comparison to last winter would be “Similar, but yet, so different.” La Nina is scheduled to make a return over the next couple of months. Atmospheric indicators have shown amplification of the residual La Nina-like pattern lingering since the spring but oceanic indicators at the surface had yet to materialize halfway through boreal autumn. This is starting to change. Beginning in late July, negative sub-surface anomalies appeared at thermo cline depth in the central Pacific and gradually spread eastward across the basin. Recently, these colder sub-surface waters have been upwelling to the surface, as shown in these most recent sea-surface temperature anomaly charts. Weather footnote, the system that brought an early arrival to winter here also brought an early arrival to winter all the way down to Mexico and may help to tilt the proverbial tipping point towards a full blown La Nina event. In a classic Tehuano wind event, a large region of cold upwelling has appeared in the Gulf of Tehuantepec. These events are normally followed by a surge in the trades across the east Pacific that may douse the remainder of the east Pacific of its surface warmth and allow the colder sub-surface waters to reach the surface completely. In addition, the upwelling portion of an oceanic Kelvin wave will propagate through the Pacific over the next month or so. This should trigger the long-awaited oceanic response into La Nina conditions by December.

So, what will make this winter similar to last?

Already apparent in the longwave pattern across the Western Hemisphere are developing positive height anomalies across the US southwest and most of the Atlantic basin, characteristic of a La Nina-like pattern. An extreme example of this last winter concluded with one of the driest ‘wet-seasons’ on record in California and every storm east of the Mississippi tracking from Missouri to Maine, leaving behind record breaking snowfall from the Great Lakes to New England and southern Canada as they rode around the periphery of a semi-permanent strong western Atlantic blocking ridge. This winter, the ridge-trough-ridge pattern won’t be as pronounced, but will still be present, leading to a majority of low pressure systems to follow a dominant storm path. However, as hinted at above, it’s been a struggle to completely return to a La Nina base-state. Since this’ll be a loosely established pattern heading into this winter, as opposed to last winter where La Nina was firmly established, there’s likely to be more variability to the weather pattern across the country this winter as strength and position of planetary ridges and troughs ebb and flow.

Also, like last winter, the oldest thickest sea-ice resides in the western hemisphere, with thin, recently formed, lower-concentration ice on the Siberian side of the Arctic. It comes as no surprise that the polar vortex early on in the season has formed over this region of thicker, high-concentration ice. This should ensure that winter will set-in across the northern-tier of the country on time this year and may do so with some bite. Longer range models have shown an immense arctic airmass developing over Alaska and western/central Canada later this month that will dive southwards into the US as boreal winter commences.

Answer, mean position of planetary ridges/troughs. Early-season availability of cold air.

However, as mentioned above, La Nina has yet to become a firmly established pattern and there are other factors that play critical roles in winter variability here in the Northeast. Those are the indices that measure the proceedings of the Arctic Oscillation (AO) and North Atlantic Oscillation (NAO). These indices correspond to the weather patterns over the arctic/sub-arctic and the North Atlantic Ocean, including Western Europe and those of us here along the east coast of North America. Unlike last winter, the NAO, which spent most of the season in positive phase, will tend to be in negative phase this winter. In doing so, there’ll be more, longer periods of Greenland blocking and ensuing downstream/upstream troughiness. This will promote a greater number of storms that undergo coastal redevelopment, holding colder air locked into the Northeast. Last year a majority of these systems remained progressive, moving through the Great Lakes to New England with little coastal redevelopment. Ultimately, timing decides everything, but with more time spent this winter under conditions favorable for coastal redevelopment and the southeastward shift in storm track due to a more negative NAO, seasonal totals along the coastal plain and northern Mid-Atlantic should be greatly increased compared to last winter. Correspondingly, this will leave northern New England south of the belts of heavy snowfall this winter, although enough variability and active storm track will bring them average to slightly above average snowfall. The likely winners in the snowfall department this winter will be from north-central Pennsylvania to interior central New England. Active, southeastward shifted storm track combined with being in deeper cold air for much of the season will lead to some large seasonal snowfall totals. This area saw many storms begin with snow, then change over to sleet, freezing rain and eventually rain as warm air surged north with every storm that moved west of the area last winter. This will be less of an occurrence this winter as warm air will fail in many attempts at spoiling the snow. Recent patterns in the AO has been for wild swings from extremely positive to extremely negative, typically taking 6-8 weeks to complete this cycle, then flattening out over the ensuing 6-10 weeks before undergoing another gyration. This had recently repeated itself twice extending back to last spring and appears to be in the midst of beginning another. Much of the month of October has been spent in positive AO but recent models show a dive into the negative starting the second week of November that may carry through to the end of the month. Following this pattern the next sharp gyration of the AO will be in late January to mid February. There’s likely to be a large East Coast snowstorm during this period.

Adding variability to the pattern will be a more pronounced negative PDO pattern across the Pacific. The large pool of below normal SST’s across the northeast Pacific, off the West Coast, and general troughiness centered over the Gulf of Alaska, a constant supply of Pacific moisture and energy will be introduced into the North American pattern. Above average storminess from northern California to southern British Columbia will lead to another season of impressive seasonal rain/snow totals while areas of southern California will continue to endure severe drought. Much of this energy will continue on through the central/northern Rockies and into the Plains with a below average number of systems becoming trapped in the Southwest. East of the Rockies, low pressure systems will tend to follow a tight baroclinic zone around the periphery of the western Atlantic high pressure. This is the pattern similar to last year. But unlike last year, the La Nina pattern in the atmosphere isn’t as strong. So there’s likely to be less of a representation of the western Atlantic ridge and greater variability in the storm track as the La Nina pattern tries to get a hold on things. Also, the NAO is forecast to spend more time in negative territory, which should flatten the top, erode, or eliminate in some cases, the western Atlantic ridge. This will account for a greater number of storms to move southeast of the dominant storm track seen last winter. This will result in less snowfall than last year’s record amounts within a couple hundred miles of the US-Canadian border region and more snowfall over the Ohio Valley, southern half of the Northeast and northern Mid-Atlantic. I would also be concerned about a major ice storm across the Carolinas and northern Georgia this winter, given the availability of arctic air this winter and a southward shifted storm track. Again, the next expected fluctuation in the AO towards the end of January sticks out as the most probable time for such an event. Freezing precipitation problems should also extend into the region outlined for greatest risk at exceeding seasonal snowfall averages. As seen last winter, there’ll be many warm advective/isentropic lift precipitation events. This is always a classic set up for warm air aloft to spoil many-a-snowstorms by changing precipitation to sleet and freezing rain.



There’s lots going on here but I’ll try to make it understandable.

Blue “H’s” are mean positions of high pressure
Red “L’s” are main development areas of low pressure systems
Red curved lines extending away from “L’s” are the dominant storm tracks, thickness of line indicates frequency; thicker=more frequent.
Black line is the mean position of the jet stream
Blue circles indicate colder than normal temperatures
Red circles indicate warmer than normal temperatures
Green circles indicate greater than average precipitation
Yellow circles indicate less than average precipitation.

The highest range of variability in storm track will be over the Pacific Northwest Coast and across the eastern half of the country centered from the mid-Mississippi Valley and the Mid-Atlantic. Broad troughiness will extend across a good portion of the country, allowing for cold Canadian air to bleed southward into the northern-tier states. Strength of coastal and near-shore ridges will determine the extent of the cold air throughout the season but the north-central states should find themselves centered under this airmass for a good portion of the winter as cold zonal flow will tend to dominate the winter pattern. Position of western Atlantic ridging will allow for the Gulf of Mexico to be tapped, as opposed to capped, as storms develop across the center of the nation. This will allow for wetter than average conditions extending from Missouri to the Northeast, similar to last year but southeast shifted a hundred miles or so given the expected southeastward shift in storm track. Dry conditions are to be expected again across the northern High Plains, the Southwest, and the Southeast.


Here in the Northeast an active winter season is expected. As mentioned above, we’ll be close to the main storm track for much of the winter season. The expected development of La Nina will keep a mainly positive PNA pattern going for much of the winter. A change from last winter will be the strongly negative PDO, and (perhaps) a weakly negative NAO. These will conspire to keep coastal ridging in check, allowing for more Pacific energy to enter the western states and allow more energy to move off the East Coast, as opposed to moving into Canada as seen last winter.

With the baroclinic zone shifted closer to the coast this winter season, a greater number of storms will redevelop upon cross the Appalachians along the coast, helping to hold cold air in across the Northeastern states. This will lead to greater than normal precipitation and snowfall across a good portion of the region. Near average snowfall can be expected across the northern third of the Northeast as this region will miss more storms to the south this season. This region will also see below average precipitation but with high snowfall ratios expected being deeper in the colder air normal seasonal snowfall totals should be achieved.





Cold air will also find its way into the Northeast with greater frequency this winter given the southward shift in the jet stream expected. At least the northern half of the region should see below normal temperatures this winter with near normal temperatures across the southern half of the region where equal bouts of cold and warm air is expected being in close proximity to the storm track.




Current watches, warnings and advisories.


Eastern US current watches/warnings

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Forecast Discussion


Mid-term - Issued - 1/17/09 @10:05am



Not much change Tuesday and Wednesday as the deep upper trough and moist cyclonic flow remains parked over the Northeast with minor shortwave disturbances rippling through the region. Scattered snow showers will remain with the highest concentration near the lakes and in upslope areas. Any accumulations will be light for the most part, generally under an inch, but the favored lake effect regions and west-facing slopes may receive as much as 3-6 inches through the midweek period. The upper trough finally relaxes some by Thursday with surface high pressure moving by just south of the region. A glancing shot of arctic air may slide across northern New England but the remainder of the Northeast should see mainly fair skies and seasonably cold temperatures averaging just 5 degrees below normal.


Long-term - Issued - 1/17/09 @10:05am



Complications begin to arise by Friday, as a major pattern shift appears to once again be underway. The western ridge will begin to breakdown and allow more Pacific moisture/energy to enter the nation. First, we must get through one more northern stream disturbance that will spread another round of snow showers across the Northeast. This system will also be accompanied by an arctic front that will drop another much below normal airmass into the region. However, this arctic airmass won’t be nearly as cold as the one we’re currently dealing with and won’t last nearly as long, moving out of the picture by next Sunday. We begin to feel the pattern change here in the Northeast the following Monday as the first in perhaps a series of Pacific systems march across the country as the good ol’ La Nina pattern seems to take shape once again.




___________________________________________________________


Radar: Northeast Region Loop

NE radar

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Current snowcover

Northeast Snowcover


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Local SST's

Northeast SST's


___________________________________________________________

2008-09 Winter Forecast


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Updated: 5:24 AM GMT on January 22, 2009

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Arctic air and snow

By: sullivanweather, 3:05 PM GMT on January 17, 2009

Current watches, warnings and advisories.


Eastern US current watches/warnings

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Forecast Discussion


Synopsis - Issued - 1/17/09 @10:05am



A duo of clippers diving into the deep upper trough over the eastern US will bring snow to the Northeast over the next several days. Light to moderate accumulations are expected across most of the region with significant snowfall possible over New Hampshire and Maine as the first low undergoes coastal reformation and taps into some Atlantic moisture. The airmass over the Northeast within the upper trough slowly modifies through the midweek period but remains below normal for the duration. By Friday another trough moves into the region but the details on the evolution of this feature are still sketchy though it does appear another arctic airmass will follow its passage for next weekend.


Short-term - Issued - 1/17/09 @10:05am


A brutally cold airmass has brought extremely low temperatures to the region once again this morning. Some notable temperatures across the Northeast this morning is as follows:

Clayton Lake, Maine…-40°F
Presque Isle, Maine…-35°F
Houlton, Maine…-33°F
Caribou, Maine…-32°F
Berlin, New Hampshire…-31°F
Saint Johnsbury, Vermont…-22°F
Fryeburg, Maine…-22°F
Elmira, New York…-19°F
Westhampton, New York…-15°F (Long Island)
Bradford, Pennsylvania…-15°F
Sussex, New Jersey…-14°F
Danbury, Connecticut…-10°F

In addition, lake effect snow has been ongoing with Oswego, NY picking up 14” of snow over the last 24 hours and many other locales close to the lakes receiving 6-12 inches in that time frame. Aside from a remaining single band of lake effect snow in the Watertown, NY/10,000 Lakes vicinity that may drop an additional 3-8 inches of snow, most will begin the day with brilliant sunshine which will quickly warm temperatures from their bitterly cold morning lows. However, across the western third of the region, high clouds have already filtered in and will gradually overspread the remainder of the Northeast during the day. Some light snow may reach the Niagara Frontier by dusk, but most of the precipitation associated with the approaching clipper low should hold off until after dark. As mentioned above, high temperatures today will recover nicely, though still remain well below normal. Temperatures will reach the low to mid 20’s along the southern coastal plain with mainly teens across the southern interior. Further north, coastal regions will remain in the teens with only single numbers across the interior. Winds will begin to pick up out of the south, which usually is a welcome relief to the cold but with such a deep cold airmass in place it will do nothing more than to make for a biting wind chill. In fact, advisories are posted for wind chill across much of the interior for wind chills exceeding –15°F.

Light snow will gradually overspread the Northeast tonight as isentropic lift increases out ahead of the clipper. QPF during the overnight hours won’t be too impressive, generally a tenth to two-tenths of an inch confined to the northern half of Pennsylvania and much of upstate New York. However, given the fluff factor of nearly 20:1 due to lift intersecting the prime snow dendrite growth region, amounts will range from 2-4” across these areas. Further south, across southern Pennsylvania, QPF will be less and prime snow growth doesn’t intersect the best lift, making for smaller flakes and a lower snow:liquid ratio. But given the cold dry airmass still in place, 14:1 is not out of the question for these areas and accumulations of up to an inch could be expected. The exception to this will be the Laurel Highlands where orographic lift will make up for the lack of a good isentropic upglide and 2-4” of snow will be possible. By daybreak snow will have spread into much of western New England, but accumulations should be under an inch by sunrise. With the clouds and precipitation moving in temperatures won’t be allowed to free-fall as they have done during the previous two nights. Lows will range from the teens and single digits across the interior sections of Pennsylvania, New York and western New England with upper teens to low 20’s along the coast. Further northeast across New Hampshire and Maine several hours of ideal radiational cooling conditions during the evening hours should promote a rapid fall in temperatures once again but clouds moving in during the overnight will cap temperatures. Whether or not someone considers a ‘cap’ in temperatures in the negative teens and 20’s a ‘cap’ is up to them, but taken into account temperatures have fallen to the negative 30’s and negative 40’s the past two night, ‘cap’ might be appropriate. Southerly winds will blow at 10-20mph in most areas except for New Hampshire and Maine where winds should be light and variable. These winds will once again bring wind chills below zero where temperatures fail to do so.

As the clipper moves across the Northeast on Sunday a secondary area of low pressure will develop southeast of Long Island and tap into Atlantic moisture, spread it back over New England. Snow will develop and become heavy at times, especially across southern New Hampshire to Downeast Maine, where 6 inches of snow should easily be exceeded with possible accumulations of up to a foot. Enough warm air in the boundary layer may move over Cape Cod and the islands, allowing rain to mix in with the snow at times. The remainder of the Northeast will still be under the influence of the primary low with cyclonic flow aiding in producing scattered snow showers. Additional accumulations here will range from 1-2 inches. Snow continues Sunday night across Maine with significant additional accumulations. By the time snow tapers off over a foot of snow will fall across the I-95 corridor in Maine with 6-12 inches over the remainder of northern Maine and New Hampshire. To the west scattered snow showers will begin to come in off the lakes but with a mostly frozen Lake Erie, lake effect snow there will begin to be scaled back in intensity for the remainder of the winter season. Highs Sunday will make it into the teens north and 20’s south across the interior with temperatures approaching or slightly exceeding the freezing mark along the immediate coast. Clouds and precipitation hanging around Sunday night will hold temperatures close to their Sunday highs.

Additional energy rounding the base of the trough will spawn another area of low pressure offshore Sunday night that may move close enough to the coast for a second round of snowfall late in the overnight into Monday but this will be confined to the immediate coastal areas of eastern Long Island, Cape Cod and Downeast Maine. This second feature may drop an additional 1-3 inches of snowfall but the main story will be the first clipper low. However, a slight change in track towards the west may bring higher amounts of snow further inland but as it looks right now this second feature will simply be a near-miss. With the upper trough axis over the region scattered snow showers will hang tough across the remainder of the region on Monday with mostly cloudy skies and temperatures remaining 5-10 degrees below normal.




Mid-term - Issued - 1/17/09 @10:05am



Not much change Tuesday and Wednesday as the deep upper trough and moist cyclonic flow remains parked over the Northeast with minor shortwave disturbances rippling through the region. Scattered snow showers will remain with the highest concentration near the lakes and in upslope areas. Any accumulations will be light for the most part, generally under an inch, but the favored lake effect regions and west-facing slopes may receive as much as 3-6 inches through the midweek period. The upper trough finally relaxes some by Thursday with surface high pressure moving by just south of the region. A glancing shot of arctic air may slide across northern New England but the remainder of the Northeast should see mainly fair skies and seasonably cold temperatures averaging just 5 degrees below normal.


Long-term - Issued - 1/17/09 @10:05am



Complications begin to arise by Friday, as a major pattern shift appears to once again be underway. The western ridge will begin to breakdown and allow more Pacific moisture/energy to enter the nation. First, we must get through one more northern stream disturbance that will spread another round of snow showers across the Northeast. This system will also be accompanied by an arctic front that will drop another much below normal airmass into the region. However, this arctic airmass won’t be nearly as cold as the one we’re currently dealing with and won’t last nearly as long, moving out of the picture by next Sunday. We begin to feel the pattern change here in the Northeast the following Monday as the first in perhaps a series of Pacific systems march across the country as the good ol’ La Nina pattern seems to take shape once again.




___________________________________________________________


Radar: Northeast Region Loop

NE radar

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Current snowcover

Northeast Snowcover


___________________________________________________________

Local SST's

Northeast SST's


___________________________________________________________

2008-09 Winter Forecast


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Updated: 3:25 AM GMT on January 19, 2009

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Arctic invasion!

By: sullivanweather, 1:01 PM GMT on January 13, 2009

Current watches, warnings and advisories.


Eastern US current watches/warnings

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Forecast Discussion


Synopsis - Issued - 1/13/09 @8:05am


The Northeast will find itself in the icy depths of winter by weeks end. Arctic air will be ushered into the region via two clippers, each with progressively colder air behind them. Each one should bring advisory level snowfall to portions of the region. The first clipper set to move in on Tuesday across the north. The second clipper slated for Wednesday into Thursday, a bit further south. When Friday rolls around temperatures will range from 10-20 degrees below normal. A bit of moderation by the weekend but another clipper will spread snow showers across the region.


Short-term - Issued - 1/13/09 @8:05am



Two stories today. One, a clipper with a strong arctic cold front that will bring numerous snow showers and a few squalls to the interior, and two, a developing area of low pressure off the East Coast. Will focus on the clipper/front first.

A 1008mb low is analyzed over the western shores of Lake Huron with a surface cold front extending though the Ohio Valley. Numerous snow showers have developed out ahead of this feature and will move into western Pennsylvania and New York this morning and spread into central sections of the region this afternoon. Snow showers may even mix with rain across the valley locations in southern Pennsylvania. Accumulations will be light, an inch or two in the mountains and across the Niagara Frontier with lesser amounts in the valleys and lowlands. In the late morning and early afternoon, the surface front will move into the region and despite the best moisture and upper support moving well northwest of the region, the front will move into a dynamic atmosphere. Surface temperatures out ahead of the cold front will rise into the mid to upper 30’s across the southern half of the region, making for very steep lapse rates. The tight thermal gradient pushing into the region with the cold front should promote the development of a band of snow squalls. These squalls are notorious for dropping visibilities near zero and dropping an inch to two inches of snow in as little as 30 minutes. Other snow showers in the vicinity of the front will also become more intense, especially in upslope areas of the Allegheny Front and southern Adirondacks where additional accumulations in the afternoon will range from 2-4 inches. Lake effect snow will add an additional 2-4” is favored areas of northwest Pennsylvania and extreme southwest New York on west-northwest flow behind the front. During the evening hours the front will lose some dynamic support with the loss of insolation but will still manage to produce scattered heavier snow showers and squalls as it moves down into the Coastal plain and southern New England. More numerous snow showers will fall across upstate New York and northern New England, closer to the proximity of the clipper. A general 1-3 inches can be expected across much of the region, with 3-5 inches across the higher terrain. Stronger snow showers in the south may produce an inch or so but even weaker snow showers will make for difficult travel and present the possibility of flash freezing as arctic air pours in quickly behind the front. The snowbelts will also see their fair share of lake effect snow with 3-6” in favored areas. Highs across the interior today will range from the low to mid 20’s across the north with teens in the higher terrain. To the south, temperatures will get quite a boost in the southerly flow ahead of the front. Highs will reach the low to mid 30’s for most and even approach 40°F in south-central Pennsylvania. Overnight lows will plummet. Between noon and daybreak Wednesday morning 850mb temps drop 16-18°C. Sunrise lows will bottom out in the teens along the coastal plain away from the immediate coast. Single digits most elsewhere across the interior with below zero readings into northern New York, Vermont and New Hampshire. The wind will be a factor as well, with strong cold air advection making for very gusty conditions overnight. Areas that are seeing snow or had snow during the day will see blowing and drifting occur. Wind chills will also drop to dangerous levels of –30°F up north. Most places elsewhere across the interior will see below zero wind chills as well with the exception of the southern costal plain, and not much better there; single digits.

The second story today is the developing low offshore. A strong disturbance as the base of the trough will link up with sub-tropical moisture streaming into the Southeast at mid and upper levels and spawn a surface low about 200 miles offshore Charleston, SC. This low will move rapidly northeastward with the bulk of it remaining offshore. However, the extreme northwestern fringes of the storm may just clip the immediate coast of southern New Jersey, the Twin Forks of Long Island, Cape Cod and Downeast Maine this evening and into the overnight as it passes by. The day starts partly cloudy and it turns out being a rather pleasant winter day, with the breaks of sun and southerly flow warming temperatures into the 40’s south, 30’s in Downeast Maine. Clouds will thicken in the late afternoon and evening with precipitation moving in after dark. Precipitation will be rain, for the most part, across southern coastal New Jersey, Long Island and Cape Cod, although a few heavier bands of precipitation, should they materialize, may switch things over to snow. As colder air with the arctic front reach these regions later on in the overnight all leftover showers will change to snow. Across Downeast Maine precipitation will be all snow throughout the event with a 1-3 inch accumulation expected. The later arrival of the front won’t drop temperatures in the overnight as much as the interior, but lows will still fall into the low to mid 20’s.

High pressure quickly builds into the region on Wednesday, providing a break in the snow, briefly. By afternoon, the next system will already have spread a vail of high clouds over the southern half of the region in advance of the next clipper. Light snow may even reach western Pennsylvania by sunset, but much of the day will be spent dry and C-O-L-D! Temperatures will rise very little during the daylight hours or simply hold steady state. Highs will be in the twenties along the coast, with teens and single digits inland. Locations across far northern New York and New England may not even reach zero. The aforementioned high cloudiness may present plenty of opportunity for viewing certain features such as sundogs, sun pillars, halos, arcs and other phenomenon. Be alert for these pleasurable sights but try not to stare directly into the sun when doing so!




Mid-term - Issued 1/13/09 @8:05am


The next clipper system moves through southern Pennsylvania Wednesday night and Thursday with widespread light snow for most of the southern half of the region. There may be a band of moderate snow in the deformation band to the northwest of the snow track as well. QPF is light with this storm, ranging from a tenth to a third of an inch. But due to the nature of the airmass in place, snowfall ratios will average 16-22:1, turning a minor event into something a bit bigger. The low will also need to be watched as it pulls offshore and possibly adds in at least a little Atlantic moisture to eastern Long Island and Cape Cod. There could be several inches of snow in these locations should this occur. The bulk of the storm should pass by to the south of I-90, with just a few scattered snow showers north of here and only clouds to the far north. However, a slight change in track of the clipper towards the north could bring accumulating snow here, too. Much colder air follows this second clipper with lows Thursday night dropping below zero across much of the interior and only single digits along the coast. Lake effect snow will also follow the clipper in the arctic airmass that pours in behind it. Activity should be in thin multi-bands and accumulate another 3-6 inches closer to the lakes and 1-4 inches outside of these areas.





It continues cold on Friday with mostly sunny skies away from the immediate lake shores where lake effect snow will be ongoing, but weak, only dropping a couple more inches of snow. Temperatures will be the big story! Single digits above and below zero across the interior with only teens along the coast.


Long-term - Issued - 1/13/09 @8:05am



Another brutally cold Friday night/Saturday morning, then some weak warm advection returns ahead of an approaching clipper dropping into the Great Lakes. Snow showers will break out over the region in this warm advection pattern this weekend. Temperatures will slowly moderate but another clipper by Monday will bring arctic air back to the region by Tuesday.


Super long range forecast: 80% chance of a Groundhog seeing its shadow.




___________________________________________________________


Radar: Northeast Region Loop

NE radar

___________________________________________________________

Current snowcover

Northeast Snowcover


___________________________________________________________

Local SST's

Northeast SST's


___________________________________________________________

2008-09 Winter Forecast


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Updated: 6:26 PM GMT on January 16, 2009

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Winter storm this weekend then the arctic comes south

By: sullivanweather, 1:11 PM GMT on January 10, 2009

Current watches, warnings and advisories.


Eastern US current watches/warnings

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Forecast Discussion


Synopsis - Issued - 1/10/09 @8:05am



Another major winter storm is bearing down on the Northeast this weekend. More snow versus mix this time around although across the southern third of the region sleet and freezing rain will fall at some point during the storm. Storm will be halfway to Newfoundland by Sunday evening leaving seasonably cold air in its wake for Monday. The to affect the Northeast on Tuesday, a possible Miller type-B development but more likely just a clipper passage with the secondary remaining too far offshore. Arctic air starts to filter down into the Northeast behind the second system but more so the third, another clipper, slated to move in on Wednesday night and Thursday. It will be behind this third system that the core of a bitterly cold airmass moves in with temperatures falling 15-25 degrees below normal, with this also being the coldest time of the year climatologically speaking.


Short-term - Issued - 1/10/09 @8:05am


1010mb surface low pressure is currently organizing over the lower Ohio Valley while a 1028mb surface high rest atop the Northeast this morning. Light snow has already spilled out across much of Pennsylvania and central/southern New Jersey well in advance of this system as isentropic lift increases. Some of this snow isn’t quite reaching the ground yet, but as the atmosphere saturates, snow will slowly fill in the gaps. Temperatures this morning have been in the low to mid 20’s across a good portion of Pennsylvania and New Jersey with upper 20’s draped along the coastal plain. As one heads north, where clouds have moved in later last evening, temperatures are much colder. Much of upstate New York and central/northern New England re in the single digits above and below zero this morning thanks to several hours of ideal radiational cooling under the aforementioned high. Southern New England, southeast New York and northeast Pennsylvania are mainly in the teens at the time of this writing.


Snow will continue to overspread much of the southern tier of New York and southern New England as the day progresses today as isentropic lift increases between 280-290K. Trends in the models have been to bring this system further north, and this forecast will follow those trends. Earlier prognostications indicated a low track along the Mason-Dixon line but this will be shifted north, in accordance with the latest model trends, to a track just south of the I-80 corridor. Aloft, the track of the 850mb low has also come north, allowing for above freezing air in the 850-700mb layer to penetrate into the southern half of Pennsylvania, much of southern/central New Jersey, extreme southeast New York and along the south coast of southern New England. All this indicates that this will not be a purely snow event for these areas, with the initial batch of snow eventually mixing with sleet and/or freezing rain. Boundary layer tempers will also make a run above freezing across extreme southeastern Pennsylvania into southern New Jersey, then up the immediate coast to Monmouth County. Expect a changeover to plain rain here, as well as the eastern end of Long Island. Martha’s Vineyard and Nantucket. It will be a close call on the outer Cape as well, but for now will go with an all snow forecast there and wait for later model runs to fine tune. Where precipitation remains all snow it will begin to come down heavy at time with accumulations up to and exceeding an inch an hour during the height of the storm. QPF from this storm across the heavy snow swath with range from a half inch to three-quarters of an inch. Snow ratios will be in the 12:1 range south and 15:1 range north, where best lift/snow growth region intersect. In all expect a solid 6-10” snowfall between the I-80 and I-90 corridors across Pennsylvania and New York, with the heavier accumulations moving north of I-90 upon reaching eastern New York and New England, with southern Vermont and New Hampshire getting in on the act. Across the Adirondacks, northern Vermont, New Hampshire and extending into central Maine, accumulations will be lighter, ranging from an inch or two near the border with Canada with closer to 4-5” as one approaches the previously mentioned heavy snow band. Amounts will be detailed in an updated snowmap to be issued shortly.

By Sunday afternoon low pressure will be moving rapidly out to sea, towards the Canadian Maritimes. A few lake-effect snow showers will be left in its wake, but for the most part rapid subsidence due to high pressure quickly moving in will make for mostly sunny skies to spread over the region. High on Sunday will be in the teens north with 20’s south. Along the immediate coastal plain temperatures will approach the freezing mark. A very weak upper disturbance, without much surface representation, will move across the Northeast Sunday night. A few flurries may skirt by the Allegheny Front but, for the most part, the most this system will bring is an increase in high clouds, cutting back somewhat on radiational cooling. Temperatures Sunday night will drop below zero across the far north with single digits and teens throughout the remainder of the interior and 20’s along the coastal plain.


Snow/ice totals.



Mid/long-term - Coming 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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2008-09 Winter Forecast


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Updated: 1:10 PM GMT on January 11, 2009

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Lake effect snows today, another storm this weekend

By: sullivanweather, 4:16 PM GMT on January 08, 2009

Current watches, warnings and advisories.


Eastern US current watches/warnings

--------

Forecast Discussion


Synopsis - Issued - 1/8/09 @11:15am



Lake effect snows will plague the snowbelts today while scattered snow showers will extend over the remainder of the region as the upper trough pulls through. Transient shortwave ridge will make its way through the Northeast on Friday, ending most, if not all, of the lake effect snow but this respite will be short-lived as a potent clipper-hybrid system moves into the region this weekend. This system has the potential to drop warning criteria snowfall for a good chunk of Pennsylvania, northern New Jersey, southern New York and southern New England. Seasonably cold air will be left in its wake ahead of another clipper for early next week, behind which the floodgates to the arctic swing open delivering the coldest airmass of the season.


Short-term - Issued 1/8/09 @11:15am


Deep moisture, cyclonic flow, upper support from a H5 trough and a lingering surface trough axis hanging back from yesterday’s winter storm will keep a general area of snow showers draped across the Northeast today. Heavier snow will fall in upslope areas of the Northeast Kingdom and downwind of the Great Lakes. DeltaT’s are running between 20-22°C over the lakes with –18°C 850mb temps filtering in overhead. Flow is well aligned but will oscillate between 280-305° throughout the day; starting around 280° and gradually dropping to 305° this afternoon. Inversions are running above 800mb, so a deep mixed layer should promote heavy snowfall rates within the bands, approaching 2”/hr. By this evening, as high pressure builds in, inversions will begin to lower and the bands will once again shift towards the north as the flow returns to a 290-280° trajectory. Shear will increase and inversions will lower, spreading out the bands and lessening the intensity. Favored areas across western New York and around the Tug Hill Plateau will pick up anywhere from 6-12 inches of snowfall. Immediately outside of these regions, and across upslope areas of the west facing slopes of the Adirondacks, Allegheny Front, Green and White Mountains, accumulations will run from 3 to 6 inches. Elsewhere across the region any accumulations will be minimal, ranging from 2-3 inches across the eastern Mohawk Valley to under an inch as one heads away from the main bands. Along the coastal plains snow showers and flurries will be few and far between with partly cloudy skies. It will be quite blustery today in the cold air advection regime. Winds will be out of the west-northwest around 10-20mph with gusts to 35mph, especially across New England. This may cause some scattered power outages as ice from yesterday’s storm still hangs on tree limbs and branches. Temperatures today will rise little and likely fall during the afternoon, following an atypical diurnal trend given the strong cold air advection. Highs will range from the low to mid 30’s along the coastal plain with 20’s across much of the interior. The higher terrain of northern New York and New England is likely to see temperatures in the teens.

As mentioned above, the lake effect will settle down tonight as high pressure noses into the region. Away from the lakes/mountains, skies will be partly cloudy to mostly clear and winds will die down. Lows will range from the low to mid 20’s along the coast with teens across the interior and single digits across the higher terrain. Wind chills will also drop into the teens along the coast to below zero across the far north.

Weak surface ridge axis moves through the Northeast on Friday, likely ending the lake effect by early afternoon, despite models ending it earlier. Usually the models are too quick, by about 6 hours, to taper off the lake bands. Any additional accumulations will be light and confined to the immediate lakeshores to 50 miles downwind. Otherwise expect gradually increasing high clouds during the afternoon as the next system approaches from the west. High will be seasonably cold with temperatures along the coast in the low to mid 30s. The interior will see highs in the 20’s with teens in the higher elevations.

Clouds continue to increase Friday night, lowering and thickening as the night progresses. By midnight, snow showers will begin to filter into western New York and Pennsylvania as isentropic lift increases. Initially the atmosphere is very dry so it may take some time for the snow to make it down to the surface but eventually the column will moisten allowing for snow to break out. Any snow that does manage to make it to the surface will be light in the early stages of this storm so anywhere from a dusting to an inch should fall west of the Allegheny Front before daybreak. Towards the east skies will gradually become cloudy but enough time will be spent under clear skies and light winds for ideal radiational cooling conditions to be met. Lows will range from the single digits across the north (maybe slightly below zero in the higher terrain and northern Maine), to the teens elsewhere across the interior. Along the coastal plain lows will fall into the low to mid 20’s.


Mid-term - Issued 1/8/09 @11:15am

Preliminary Snowmap*



*subject to change



For being a 5th/6th period event, the ‘clipper-hybrid’ low on tap for Saturday still has many issues to be resolved in the models and uncertainty regarding track, timing, temp profiles, QPF remain high. For now, a 00Z ECMWF/GGEM blend weighted towards the ECMWF appears to be the way to go, given the track record of both models in the mid-term of recent times. This blend would take low pressure on a track across the Mason-Dixon line, spreading snow across much of the southern half of the region during the day on Saturday, perhaps mixing with sleet/rain south of the PA turnpike/I-95 corridor. Won’t get into details at this early stage given the uncertainty that remains but the potential exists for high-end advisory/low-end warning criteria snow north of I-70 to NYS-17/I-86 on eastwards to southern New England. Snow will end from west to east Saturday night (Pennsylvania) to Sunday morning (New England) with lake effect in the cold air advection behind the system.


Long-term - Issued - 1/8/09 @11:15am



In the long term, the northern stream will dominate, sending another clipper towards the Northeast by Monday night, then another stronger clipper towards the region on Wednesday. This second clipper in the long term will carry with it a strong arctic front that will bring some ridiculous cold into the Northeast. 850mb temps drop in the –22°C to –28°C range with 1000-500mb thickness values plunging to sub490dm. Break out the parkas!!



___________________________________________________________


Radar: Northeast Region Loop

NE radar

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Current snowcover

Northeast Snowcover


___________________________________________________________

Local SST's

Northeast SST's


___________________________________________________________

2008-09 Winter Forecast


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Updated: 7:53 PM GMT on January 09, 2009

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Significant winter storm to impact the Northeast

By: sullivanweather, 10:23 AM GMT on January 06, 2009

Current watches, warnings and advisories.


Eastern US current watches/warnings

--------

Forecast Discussion


Synopsis - Issued - 1/6/09 @5:30am



A significant winter storm will move into the Northeast on Tuesday and linger into Thursday with lake effect snows left in its wake. Another area of low pressure will approach by Friday and Saturday, bringing more wintry weather to the region. This second system will be followed by an arctic blast that will drop temperatures well below normal for the foreseeable future.


Short-term - Issued - 1/6/09 @5:30am


An extremely complex weather situation is currently unfolding that promises to bring a prolonged winter weather event to the Northeast. The next question is where to begin?? In the southern stream, several shortwave disturbances, along with their attending surface lows, are riding a strong 140-160kt sub-tropical jet stream out of Texas, up the Tennessee Valley, across the Mid-Atlantic and off the coast. Deep sub-tropical moisture (Precipitable water values in excess of an inch) south of the aforementioned line is helping to bring much needed rainfall to the drought-stricken Southern Appalachians; where up to 2-4” of rain is possible. The main pocket of energy in the southern stream is still lingering back over northern Mexico and this will be pulling northeastwards today. Meanwhile, in the northern stream, a tough digging into the Northern Plains will eventually link up with this southern stream energy, partially phasing both jet segments across the eastern half of the country. I mention partially because this entire storm system will remain rather disjointed, a double-barreled storm with no dominant area of low pressure forming until the entire mess reaches the Canadian Maritimes. The result of the northern and southern streams coming together will be building heights off the Southeast Coast that will eventually lift this whole mess towards our region of the country this afternoon. Apparent on satellite imagery is a thickening shield or mid/high level clouds that as already pushed as far north as the New York/Pennsylvania border. These will gradually expand northeastwards as the day progresses with precipitation not far behind.

But first things first. Currently, high pressure rests atop the Northeast, albeit weak, with a central pressure of merely 1018mb. There are still some scattered lake-effect flurries coming off Lake Ontario in light westerly flow on the north side of this high combined with marginally unstable lake-effect parameters but these shouldn’t amount to anything more than an inch, at most. High clouds have already overspread the southern half of the region and these should lower and thicken as the morning progresses. Precipitation is not far behind the advancing cloud shield, with light rainfall being reported just south of the Mason-Dixon line at Maryland ob sites. Increasing isentropic lift will cause precipitation to blossom across Pennsylvania south of the turnpike by noon, eventually overspreading the remainder of the commonwealth, as well as New Jersey and the southern half of New York by evening. The precipitation should start as snow across a majority of the region as the entire column is below freezing. But increasing warm advection will create a wedge of warmer air in the 850-700mb layer that will begin to turn the snow over to a mixture of sleet and freezing rain across southern Pennsylvania but not before an inch or two of snow accumulation. Along the immediate coast the precipitation should also start as snow but an increasing easterly fetch off the relatively warmer ocean waters will make for a changeover to rain as boundary layer temps warm above freezing quickly. The changeover to plain rain should also come rather quickly to southwestern Pennsylvania as there’s little to hold the cold air in place across the west side of the Appalachians as the primary low heads in that direction. To the north there will just be a general increase in clouds today, with precipitation holding off until the evening/overnight hours (upstate New York, southern/central New England) or Wednesday (northern New England). Highs will be in the 20’s across a good portion of the interior east of the Appalachians, with the exception being the higher terrain of northern New York and New England where temperatures may remain in the teens. Along the immediate coast of New Jersey and across southwestern Pennsylvania temperatures should eventually climb above freezing, into the mid to upper 30’s. From New York City northward along the coast temperatures should remain just below freezing, in the upper 20’s to low 30’s. Surface ridge axis across upstate New York across central New England will divide the wind flow across the region. To the north of this axis winds will be from the west to northwest around 5-15 mph while south of this axis (and east of the Appalachians) winds will generally be out of the east-northeast around 5-15mph. West of the Appalachians winds will be more from a southerly to southeasterly direction, gain around 5-15mph.

Things start to get really messy tonight as snow will overspread the remainder of upstate New York and southern/central New England. Increasing warm advection will also start to bring the transition zone northwards, likely reaching the NY/PA border region and eastwards to the Mid-Hudson Valley/Connecticut River Valley just after midnight, and then continuing on north to the I-90 corridor (NYS Thruway/Mass Pike) by daybreak. Along the northern edge of the transition zone a deep enough layer of cold air will exist (for the surface to ~900mb) for mainly sleet. However, south of the NY/PA border, across much of central Pennsylvania and interior southeast New York/southern New England the layer of cold air from the surface on up will be much thinner. Here precipitation will likely transition to mostly freezing rain, which should begin to cause some problems. A coastal low developing along the warm front off Delmarva, along with confluent flow over northern New England, will help to lock in the cold air at the surface, as ageostrophic winds turns to the northeast, despite the primary low heading well west of the region up towards the Great Lakes. After the transition to freezing rain QPF should range from a third of an inch to two thirds of an inch. This may be enough to bring down tree branches, eventually causing power outages over a widespread area in the above mentioned areas. While this event doesn’t look nearly as severe as the December ice storm, there will be significant disruptions. Along the coast precipitation will eventually changeover to plain rain. Strong low-level frontogenesis in the vicinity of the coastal front will lead to heavy precipitation amounts, well in excess of an inch, which may lead to urban flooding, swollen ditches and ponding water in parking lots. To the north where mostly snow falls accumulations overnight will range from 3-6”. Overnight lows are likely to hold steady over much of the region or even rise a couple of degrees, especially along the coastal plain where increasing levels of maritime air will be introduced.

Coastal low begins to get cranking on Wednesday, eventually becoming as strong as the primary by evening. Across the northern interior, precipitation will continue in the form of snow, adding up to another 3-6”. Along the coast precipitation will continue as rain, which may fall heavy at times but in between is where the real trouble will lie as sleet and freezing rain will continue as the low-level cold air will be unyielding. A dry-slot will eventually work into central Pennsylvania and New York, tapering the precipitation off to a showery regime, however, the damage will already have been done with up to an half inch of ice accretion falling across a wide area. Details will be shown in map form following the discussion. By Wednesday night heights crash as the upper trough axis pulls through and cold air advection strengthens, changing any leftover showery precipitation over to snow. Across northern New England snow will be ongoing, falling heavy at times with additional accumulations of up to a half foot.

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Maps.

Ice accretion





Snow/sleet




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Radar: Northeast Region Loop

NE radar

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Current snowcover

Northeast Snowcover


___________________________________________________________

Local SST's

Northeast SST's


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2008-09 Winter Forecast


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Updated: 2:40 PM GMT on January 08, 2009

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Midweek storm on the way followed by a significant pattern change

By: sullivanweather, 11:38 AM GMT on January 03, 2009

Current watches, warnings and advisories.


Eastern US current watches/warnings

--------

Forecast Discussion


Synopsis - Issued - 1/3/09 @6:30am


Outside of the snowbelts and upslope area of New England, Saturday should be a fair day with ridging at the surface and aloft building into the Northeast. A weak system moves into the region on Sunday, followed by a break for Monday. Then a complex area of low pressure will move out of Texas towards the region by late on Tuesday. This system promises to bring significant QPF to the Northeast through midweek. Mean trough axis sets up over the Eastern US following the departure of the midweek storm system with lake effect snows and below normal temperatures.


Short-term - Issued - 1/3/09 @6:30am



Aforementioned ridge, while weak, will build into the western half of the region today, clearing the skies and eventually ending the lake effect snows over upstate New York as the inversion lowers to around 900mb, although a few flurries may still skirt by given these events sometimes don’t give up the ghost. Meanwhile, a deep vertically stacked low over the Canadian Maritimes will keep New England in cold cyclonic flow throughout the day with weak shortwaves rotating around it southwestern flanks. Mostly cloudy skies will be present here with numerous snow showers across the higher terrain. Accumulations will be light, no more than a couple inches, so basically a nuisance for hardy New Englanders. Temperatures will range from the low to mid 30’s across the southern interior and along the coastal plain, to the 20’s across most of the remainder of the interior except for the higher terrain and northern Maine where temperatures will only struggle to climb into the teens. Winds will become light and variable over the western half of the region under the influence of high pressure but across New England it will remain quite gusty, with winds of 15-25mph along with some higher gusts.

Warm advection beings in earnest tonight as 850mb temps warm above 0°C for a good portion of Pennsylvania, New Jersey and western New York. Mid/high level cloudiness will gradually overspread much of this area, putting a cap on temperature falls. The vertically stacked low over the Maritimes will fill and begin to lift out, with weakening cyclonic flow over New England ending precipitation chances there during the evening hours leading to partly cloudy skies for the overnight. Temperatures will fall into the 20’s across the southwestern third of the region before halting their drop around midnight, then slowly begin to rise again towards daybreak as a deeper wedge of milder air moves in. Across upstate New York and New England the warm advection will have less of an impact early on with temperatures dropping back into the teens and single digits (far north) before they too put the brakes on and begin to rise towards daybreak. Winds will be light and variable over a good portion of the region except for northern Maine where a light northwesterly flow will continue.


Precipitation moves into western/southern Pennsylvania during the morning hours as a weak trough of low pressure approaches. This area of precipitation will expand into south-central New York by the afternoon. Most, if not all, of this should fall as liquid rain, although there may be pockets of sleet/freezing rain at the onset, which may persist across the higher elevations of the Allegheny’s and northwestern Pennsylvania through the afternoon. Precipitation amounts should be light, generally under a tenth of an inch. Further to the north and east expect a mainly cloudy dreary day in the warm advective pattern with only northern Maine seeing some breaks in the clouds. Temperatures will warm close to 40°F across southwestern Pennsylvania and along the coastal plain. A weak cold air damming signature is present east of the Appalachians that should keep central Pennsylvania and New York held in the mid 30’s. Across the remainder of the interior temperatures will range from the mid 20’s far north to the low 30’s.

The weak trough continues to move through the Northeast Sunday night spreading precipitation across much of the region during the overnight hours. Across upstate New York and interior New England much of this will fall as light sleet and/or freezing drizzle, eventually changing to scattered snow showers as colder air eventually filters into the region. Further to the south, precipitation should remain in liquid form. Temperatures will be in the 30’s south, with 20’s to the north.


Mid-term - Issued - 1/3/09 @6:30am



A cold front pushes through the Northeast and offshore during the day on Monday. Airmass looks marginally cold enough for lake effect snow showers to develop downwind of the lakes in its wake. Elsewhere it should be partly cloudy with scattered flurries across the higher terrain in cyclonic upslope flow. Temperatures will rise very little in strong cold air advection and should fall after the noon hour across a good portion of the region. High pressure builds in Monday night and Tuesday as the next system of concern develops in the southern stream across the Deep South and Texas.


Long-term - Issued - 1/3/09 @6:30am


A very complex forecast follows for the long-term as models are having their usual difficulties regarding the southern stream system and eventual phasing with a northern stream trough that will bring a significant winter weather event to the Northeast during the midweek period. Will keep it simple for now and call for snow to the north with a snow to mix scenario for the southern portions of the region that should eventually change on over to rain along the coast. Still lots of time to watch this one and models will likely go back and forth as to which surface low becomes the dominate feature, the coastal or the primary over the Ohio Valley. ECMWF model favors the Ohio Valley low, which would bring milder air across the region while the GFS places more emphasis on the coastal leading to a colder scenario. The Canadian GGEM model is somewhere in between but all point to at least a half inch of QPF region-wide from this double barrel storm system. Much colder air follows behind this system as a deep trough sets up shop across the Eastern half of the US by week’s end bringing below normal temperatures back across the region with lake effect snow showers in a northwesterly flow regime.



___________________________________________________________


Radar: Northeast Region Loop

NE radar

___________________________________________________________

Current snowcover

Northeast Snowcover


___________________________________________________________

Local SST's

Northeast SST's


___________________________________________________________

2008-09 Winter Forecast


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Updated: 11:39 AM GMT on January 03, 2009

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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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