Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 251828 AFDCTP Area Forecast Discussion National Weather Service State College PA 228 PM EDT Sat Mar 25 2017 .SYNOPSIS... A cold front will sag southward across Pennsylvania this afternoon and tonight, before returning north as a warm front late Sunday and Sunday night. Unsettled conditions will continue through the middle of next week before high pressure returns with drier air. && .NEAR TERM /THROUGH TONIGHT/... Meso-anal shows an west-east boundary strung out just north of I-80. The thickest clouds are over northern PA along and north of the front with brighter skies over southern PA where a mix of sun and clouds is common. The boundary will continue to settle slowly south throughout the day so by mid afternoon, it will actually start to cool over the northern half or so of the forecast area. The HRRR suggests that by nightfall it will have moved through southern PA, with the possible exception of the far SW. Rainfall amounts are expected to be on the light side. More likely we will see a pattern developing where we have widespread low clouds with scattered rain showers and areas of drizzle and fog. Overnight lows will range from the mid 30s over the NE to mid 40s over the SW. These will average some 10-20 deg above normal. && .SHORT TERM /SUNDAY/... The light showers...with areas of drizzle/ridge top fog are likely to continue through much of the day Sunday. Local experience suggests we lean away from blended model guidance for max temps in such low level cold air damming situations. As such, I lowered tomorrrow`s highs by a few degrees counting on a day not nearly as nice as today, temperature-wise. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
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This period starts out with above normal heights over the eastern US. Several lows weaken as they move into this blocked flow and are forced to move to our west. The first wave is comes overnight Sunday into early Monday. It has a good surge of moisture and a boundary related to the cooler weather on Sunday. Thus nearly all guidance shows a very high probability of rain overnight Sunday into Monday. Most of the NCEP guidance shows the peak chance of rain from 0000-1200 UTC Monday. Then things improve during the day Monday. Our POPS Monday may be too high but they are consistent with nearby offices. GEFS implies little or no rain in our CWA much after 1800 UTC. Most rain before than would be in the east. Our 850 hPa temperatures are above normal too so should be a warm later afteroon and evening. The second wave moving up to our west comes in overnight Monday into Tuesday. Clearly the uncertainty with this and the longer forecast length introduces more uncertainty. But at this time peak rain probabilities are during the day Tuesday but lower probabilities than the first event. The second event will push the warm moist air to our south Tuesday night into Wednesday. Chance of rain should drop overnight Tuesday into Wednesday. Wednesday should be a relatively good day as high pressure builds in from the northwest. The dry air and high pressure are in all the guidance implying Wednesday and Thursday should be relatively nice days. High pressure, dry air, and normal to slightly below normal 850 hPa and 925 hPa temperatures imply near normal daytime highs. The storm track shifts to our south and some models show a southern stream wave Thursday night and Friday. This could bring clouds to our region. GEFS and CMCE imply we could be on the northern edge of an expanding precipitation shield Friday and Saturday as the southern stream wave slides to our south and east. Thus POPS increase Friday and Saturday. Could be a cold rain across south-central PA Friday and Friday night.
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&& .AVIATION /18Z SATURDAY THROUGH THURSDAY/... Frontal boundary over northern PA will be pushed southward through the airspace toward the PA/MD line by 25/00z as strong high pressure builds over eastern Canada. Increasing low level moisture and wind shift to the east-northeast should translate into a lower trend in ceilings and visibility from north to south with widespread MVFR to IFR restrictions likely by tonight, lasting into Sunday. Scattered light rain showers will be possible today especially near the southward-moving frontal zone with pockets of fog/drizzle overnight into early Sunday morning. The front should lift back to the north on Sunday which should allow for at least some marginal improvement especially over portions of the southern airspace. Outlook... Sun...VFR-MVFR western 1/4 with low risk for thunderstorm in the evening. MVFR-IFR central and east with drizzle/fog. Mon-Tue...Sub-VFR with periods of rain. Wed-Thu...Becoming VFR. No sig wx. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...La Corte SHORT TERM...La Corte LONG TERM...Grumm AVIATION...La Corte is the U.S. government's official web portal to all federal, state and local government web resources and services.