Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 252317 AFDCTP Area Forecast Discussion National Weather Service State College PA 717 PM EDT Sat Mar 25 2017 .SYNOPSIS... A cold front will sag south of Pennsylvania this evening, then return 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 /UNTIL 6 AM SUNDAY MORNING/... Backdoor cold front just pushing through KUNV last hour, accompanied by a wind shift to the northeast and a 1-hour temp drop from 72F to 54F. Near term model output indicates the front will clear even Somerset County by around 02Z. Parent shortwave and associated large scale forcing is passing by to the north of Pa early this evening, so expect any remaining showers across the eastern counties to dissipate by around 00Z. Later tonight, expect some patchy drizzle to form over the higher terrain, as moist easterly flow overspreads the region behind cold front. Overnight lows will range from the mid 30s over the NE to mid 40s over the SW. These numbers are some 10-20 deg above normal. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM 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 SATURDAY/... 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. && .AVIATION /23Z SATURDAY THROUGH THURSDAY/...
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Can see the cold front on the radar earlier, just south and west of the office. CIGS not real low, even at BFD. For 00Z TAF package, did slow down how fast conditions go downhill. Overall expect a wide range of conditions later tonight into Sunday, as colder air just to the north trys to work southward. Conditions could improve some late Sunday afternoon, before a band of showers moves eastward from the Ohio Vly. Things could improve some on Monday, as some models bring the warm front back north of the area. The cold front could sag southward of the area on Tuesday, but perhaps not by much. Outlook... Mon-Tue...Sub-VFR with periods of rain. Wed...Chance of showers across the south early. Becoming VFR. Thu...No sig wx.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...Fitzgerald/La Corte SHORT TERM...La Corte LONG TERM...Grumm AVIATION...Martin

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