Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 010322 AFDCTP Area Forecast Discussion National Weather Service State College PA 1022 PM EST Wed Nov 30 2016 .SYNOPSIS... A large upper trough and pool of colder air will move across the region over the next 12 to 24 hours. The cold air and westerly winds may trigger snow showers in northwestern Pennsylvania. A series of troughs in the west will slowly build a ridge over the eastern US early next week. It should warm up again ahead of another 500 mb trough and cold front later next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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Large area of showers pushing out of my eastern counties associated with strenghtening LLJ lifting over the northern Mid Atlantic region...acting on soupy 1.25"+ PW air mass that covers the eastern third to half of central PA. Sfc cold front with NCFRB slowly pushing into the Alleghenies late this evening as per regional radar mosaic. Sfc wnds g25-29kts with this feature across western PA. Cold front which will move across the area overnight. Mild air across central and eastern PA will be displaced quickly after FROPA with temperatures falling through the 40s and into the 30s. Rainfall will taper off to showers behind the front as well. Under NW post frontal flow the showers will tend to favor the mountains of the north and west.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... Area under trough and NW flow Thursday. This will bring plenty of cloud cover but limited snow shower activity mainly in the higher elevations. Where it does snow, accumulations will be light and mainly confined to higher elevations. Temperatures will be much cooler and closer to seasonal average. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... The cold air is in placed Thursday night and Friday. The 850 mb temperatures are not impressive, in the -4 to -6 range. The colder air and flow over the warm lakes should increase snow shower activity in northwestern PA. Some guidance implies about -8C at times. Most areas will be precipitation free Fri-Monday. Except the northwestern areas where some LES is likely this weekend. The more westerly flow is not as favorable for southwest mountains. The GEFS/NAEFS/GFS have no QPF in southwest mountains. Focused attention to minor LES snows in NW. Late in the weekend and early next week the heights and 850 mb temperature rise. Snow in NW should cut-off Saturday eve or early Sunday. Then a slow and steady warm up is implied. High pressure should be over us Sunday-Tuesday/Wednesday. Most areas will be above 0C at 850 mb by Tuesday. The issue in all the EFS is the potential cold air damming event as the low moves into the Great Lakes. It may stay cooler in the boundary layer Tue-Wed due to the surface high. The NAEFSBC and GEFS imply this in the 2m temps and the 925 mb temps. The always too wet GEFS biased our grids and has some warm advection QPF by Monday. Any QPF would be very light. IF and only IF there is precipitation there could be snow/rain-snow in northern areas until overnight Monday into Tuesday. Rain farther south and east. The GEFS and CMCE PWAT is close to normal with the first two light QPF events. Not favorable for us to get rain. Some more light QPF in the GEFS Tuesday so had chance rain showers to slight chance again Tuesday. Not too confident in this still weak pattern and low PWAT values Our best chance for rain next week will likely be in the Thursday timeframe when the cold front moves into the region. As forecast it pulls about +1 sigma PWAT into our region. Thus, it may be the best forcing mechanism. Thus the GEFS has the highest PDF based POPS Wed into Thursday. We have over a week to deal with rain to snow potential with that potential event. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... Over Susq Valley and eastern PA at 03z, a large area of rain with embedded gusty showers (as 50+ kt 850mb jet lifts through bringing LLWS) producing IFR conditions at KMDT-KLNS in high PW air mass. The rain will continue to shift gradually eastward through this evening as a warm front lifts through, with even a rumble or two of thunder poss SE of KLNS, before conditions gradually improve to VFR after 06z as westerly winds help to bring some drying to lower levels through downsloping. Cold front with NCFRB slowly pushing into western portions of cwa. Gusty showers poss at KBFD-KJST through 04z, and along and north of I-80 through 06z, but this feature will weaken over the central and southern mtns as it pushes east. Conditions will be somewhat variable ahead of the cold front (between the rain areas), but overall will transition to less and less VFR and more widespread MVFR/IFR. Post frontal WNW flow will bring long duration widespread restrictions to the mountains of the north and west starting tonight, and additionally a transition to snow showers on Thu continuing into Sat. Outlook... Thu-Sat...Sct SHSN w/ocnl MVFR/IFR in BFD-JST. Sun-Mon...Mainly VFR. Restrictions still poss NW. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Grumm NEAR TERM...Ross/DeVoir SHORT TERM...Ross LONG TERM...Grumm AVIATION...RXR

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