Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 302025 AFDCTP Area Forecast Discussion National Weather Service State College PA 325 PM EST Wed Nov 30 2016 .SYNOPSIS...
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The 500 mb trough and cold 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.
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&& .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Radar shows two areas of mainly light rain. One area is moving steadily eastward across the eastern half of the area. Another area of rain is spreading north and east from WVA and western MD into the Laurels. This area could have a few thunderstorms embedded with it as it moves across SE zones later this afternoon and evening. All of this is ahead of a cold front which will move across the area late this evening and overnight. Ahead of the front is rather mild air. The air mass will change quickly after the frontal passage 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. && .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 TUESDAY/...
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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.
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&& .AVIATION /20Z WEDNESDAY THROUGH MONDAY/... Most of the steady rainfalls has ended for KBFD...KJST...KAOO and KUNV. Farther east more rainfall and fog is possible this afternoon. IFR will dominate most of this region until this evening. We cannot rule out isolated thunderstorms in the extreme southwestern Mountains and in the KMDT-KCXY-KLNS air space. Better chance to the south and east this afternoon and early evening hours. Be mindful of thunderstorms to the south and east. The shallow cool air and warm air aloft is producing areas of strong windshear. The cold front comes through overnight and the rain moves to our west. Improving conditions overnight with more MVFR and VFR. Thursday should be a mostly VFR day. Isolated MVFR in western mountains. Outlook... Thu-Sat...Sct SHSN w/ocnl MVFR/IFR in BFD-JST. Sun...Mainly VFR. Restrictions still poss NW in the morning. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Grumm NEAR TERM...Ross SHORT TERM...Ross LONG TERM...Grumm AVIATION...Grumm/Ross

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