Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 092049 AFDCTP Area Forecast Discussion National Weather Service State College PA 349 PM EST Sat Dec 9 2017 .SYNOPSIS...
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Low pressure will move off the mid Atlantic coast tonight. A deep upper level trough will remain over the eastern conus into Thursday, before a westerly flow of milder air works into the area by next weekend. Low pressure moving just north of the area late Sunday will bring some snow to the north and west Sunday into Sunday night. Another low moving just north of the area late Monday night will bring some snow to the area late Monday into Tuesday, mainly across the north and west.
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&& .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... Regional radar mosaic and webcams continue to show accumulating snowfall over my far southeastern counties with local 2" amounts having occurred over southern York/Lancaster County as of early afternoon. Another few hours of steady snowfall expected with back edge already racing into the D.C. metro area at this hour will keep amounts very close to what we already have indicated, so no changes to amounts at this time. Steady snow will have pushed east of the area by this evening as surface low takes deeper moisture with it towards coastal New England. Later tonight, vigorous shortwave currently dropping through the midwest early this afternoon will sweep across the region tonight, as coastal low tracks into the Canadian Maritimes. Low PWATs in advance of this feature will limit precip to mainly scattered flurries late this evening. However, chilly westerly flow behind this feature is likely to generate lake effect snowfall late tonight into Sunday across the Allegheny Plateau. Northwest Warren County is favored for 3"+ in this scenario and will issue Winter Weather Advisory for late tonight through Sunday afternoon there with lesser amounts south and east of there. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/... Aside from aforementioned lake effect snow into Sunday afternoon, downsloping subsidence should result in partly sunny, dry weather east of the mountains Sunday. Mixing down model 850mb temps of -10C to -12C translate to below normal max temps Sunday, ranging from the upper 20s over the Alleghenies, to the mid 30s in the Susq Valley. A gusty west wind will add an additional bite to the air. Bukfkit soundings support frequent gusts of around 20kts.Chilly westerly flow behind the aforementioned vigorous is likely to generate a bit of lake effect snow late tonight into Sunday across the Allegheny Plateau. Ensemble qpf supports accums generally less than an inch across the Allegheny Plateau tonight/Sunday. However, favored snowbelt of northwest Warren could be near 3 inches. Later shifts may want to consider an advisory for Warren, with the benefit of later HREFV2 data. && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
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A weak low moving north of the area will bring a northwest flow of air to the area late Sunday into early Monday. This will result in some snow showers. A stronger low moving across upstate New York on Tuesday will bring some snow to the area late Monday night into Tue. THis will be followed by a cold northwest flow across the Great Lakes. This will result into some snow showers off the lakes. The west coast ridge weakens some toward next weekend, which will result in a westerly flow of milder air working into the area. Minor changes to the package. Went with dry conditions next weekend.
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&& .AVIATION /21Z SATURDAY THROUGH THURSDAY/...
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VFR conditions north...transitioning to MVFR to IFR southeast as snow impacts especially York and Lancaster Counties. Best window for reductions in the Lower Susq will be through 00z, while remainder of CWA remains primarily VFR. Then focus will shift to a trough moving in from the NW tonight, bringing restrictions and widespread snow showers to the northern/western mountains along with brisk NW flow and the potential for scattered heavier squalls that will linger into the first half of Sunday. Scattered snow showers will bring intermittent MVFR incursions into the central mountains, while downslope flow will keep the SE VFR. Outlook... Sun...AM snow showers/reductions likely Allegheny Plateau, becoming confined to the NW mtns in the afternoon. Scattered squalls also poss. Mon...Cig reductions likely western portions. PM light snow developing, mainly northwest Pa. Mon night and Tuesday...Periods of light snow. Widespread MVFR likely, with periods of IFR and brief LIFR cigs and vsbys. Wed...Reductions poss west in sct snow showers. Otherwise VFR. Thu...Still a chance of a few snow showers.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 1 AM to 3 PM EST Sunday for PAZ004. Winter Weather Advisory until 8 PM EST this evening for PAZ065- 066. && $$ SYNOPSIS...DeVoir/Fitzgerald/Martin NEAR TERM...DeVoir/Fitzgerald SHORT TERM...DeVoir/Fitzgerald LONG TERM...Martin AVIATION...DeVoir/Martin/RXR

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