Northeast Weather Blog

Current watches, warnings and advisories.




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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!!



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Radar: Northeast Region Loop



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Current snowcover




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Local SST's




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2008-09 Winter Forecast


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