Area Forecast Discussion
Issued by NWS State College, PA

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633 FXUS61 KCTP 202303 AFDCTP Area Forecast Discussion National Weather Service State College PA 703 PM EDT WED JUL 20 2016 .SYNOPSIS...
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High pressure over the eastern Great Lakes will build southeast across Pennsylvania tonight, and then off the Mid Atlantic coast Thursday and Friday. Pennsylvania will be on the northern edge of a subtropical ridge through next weekend with shortwave passages likely Friday and Monday.
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&& .NEAR TERM /UNTIL 7 AM THURSDAY MORNING/...
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Sky clearing nicely and no cu left around the area at 7 pm. Patchy high clouds are all that will mar the otherwise clear sky this evening. Upstream conditions and subsidence should keep it clear overnight. Temps do get back below 50F in the north overnight, so some fog is again expected in - only - the river valleys of the N. Prev... Mostly sunny conditions prevailing at mid afternoon with low humidity thanks to 1026 mb sfc high moving east of Lake Erie. Cirrus streaks streaming from the eastern GLAKS barely dimming the abundant sunshine for what will be a great late summer afternoon and evening. Similar to last night...skies will be mostly clear tonight and with anomalously low PW and boundary layer moisture...it will cool off nicely again after dark. We won`t see the lower 40s that occurred over parts of the northwest mountains...but mins will range from around 50F northwest to the lower 60s southeast. Winds will be light to calm.
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&& .SHORT TERM /7 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... High pressure will have crossed the commonwealth overnight...and will move off the Mid Atl coast Thursday...allowing return sw flow to advect warmer and more humid air into the state starting Friday afternoon. Large scale subsidence and still low pwats should ensure another dry day with abundant sunshine. GEFS mean 8h temps arnd 18C should translate to max temps from the m80s ovr the high terrain, to near 90F in the valleys. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... Big story in the extended fcst is expected heat wave Friday into early next week, as axis of subtropical ridge shifts from the plains to the northeast conus. Passage of a weak cold front will likely produce sct convection late Friday into Saturday morning. However, parent shortwave is progged to pass well north of PA, so only sct overnight convection is expected, primarily over northern PA. Behind this feature, 12Z GEFS indicates anomalous upper lvl ridging building ovr PA, which should bring hot wx and suppress convection. Best upcoming chance of shra/tsra comes Monday ahead of next shortwave working across the Great Lakes. Latest ECENS/NAEFS mean 8h temps are near 20C Friday through Monday, indicating the potential of several days in a row with highs in the 90s in the valleys. Heat indices around 100F appear possible by Sun/Mon across the Susq Valley, as higher dewpoints are advected into the area. Overnight lows are also a concern as the area doesn`t cool off at night through the weekend with Southern PA lows in the 70s. && .AVIATION /23Z WEDNESDAY THROUGH MONDAY/... Just some high clouds at times this aft. VFR conditions will prevail through Thursday. Increasing humidity levels Thursday Night into Friday could result in an isolated shower or thunderstorm, mainly across northern sections of the airspace. The weekend looks to be mainly dry and hot. Some haze and fog could occur each morning. Some chance for showers and thunderstorms on Monday with a cold front. Best chance again would be to the north. OUTLOOK... Thu Night and Fri...Isolated showers and thunderstorms impacts possible. Sat...Patchy fog possible early...otherwise no sig wx. Sun...Patchy fog possible early...otherwise No sig wx. Mon...Restrictions possible with chance of shra/tsra. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...DeVoir/Fitzgerald NEAR TERM...Dangelo/DeVoir SHORT TERM...Fitzgerald LONG TERM...Fitzgerald/Ceru AVIATION...Martin

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