Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 230356 AFDCTP Area Forecast Discussion National Weather Service State College PA 1156 PM EDT Tue May 22 2018 .SYNOPSIS... Low pressure will track down the St Lawrence River Valley, dragging a cold front through the region overnight. High pressure will build southeast into the region for the second half of the week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... 01Z radar loop shows scattered convection across the northwest half of Pa in advance of a shortwave pressing southeast from the Grt Lks. SPC mesoanalysis still showing CAPES near 1000 j/kg across the western portion of the forecast area, but based on radar trends and cooling/stabilizing boundary layer after sunset, believe the threat of severe weather is rapidly diminishing. Decent large scale forcing and anomalous PWATs should result in fairly good coverage of showers/storms with passage of shortwave between 00Z-06Z. Have painted the highest (likely) POPS across the central counties based on radar trends and latest HRRR, with somewhat lower POPS across the northwest and southeast counties. Drier air and a diminishing chance of showers is expected late tonight, as shortwave and associated surface cold front push south of the area. Model soundings indicate low level moisture trapped beneath inversion will produce residual low clouds and patchy drizzle late tonight over the northern mountains and Laurel Highlands. Downsloping subsidence across the Susquehanna Valley should result in partial clearing across that part of the state late tonight. However, light winds and wet ground could result in some patchy fog around dawn. Latest NBM/Superblend supports min temps ranging from the mid 50s over the northwest mountains, to the low 60s across the southern tier counties. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... Any low clouds or fog should mix out by late morning, as drier northwest flow works into the state behind cold front. Model soundings support mainly sunny skies across the entire area by afternoon. Mixing down model 850mb temps of 12C should translate to high temperatures ranging from the mid 70s over the Alleghenies, to around 80F across the Susquehanna Valley. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... Look for high pressure and dry weather Wednesday night through Friday with seasonable morning lows and warm afternoons. Saturday is trending drier and will probably be the warmest day of the holiday weekend with most locations in the 80s. 12Z mid to long range models continue to show an approach trough that will swing through the great lakes. With streaming southwesterly moisture and max temps in the 80s, Saturday afternoon could see some convection. Sunday into Memorial day could continue to see more unsettled, humid and a little cooler weather. While there will be pops in the forecast, still uncertain exactly how wet things will turn out. && .AVIATION /04Z WEDNESDAY THROUGH SUNDAY/... IFR to Low IFR persists across the region near and to the east of the Susq Valley thanks to cool, light and moist easterly llvl flow on the east side of a quasi-stationary front. Elsewhere, areas of MVFR and localized IFR Cigs will occur through 06-08Z before a period of more widespread IFR cigs develop across the Laurel Highlands and NW Mtns of PA (KJST to KFIG and KBFD) as a light nw upslope flow develops in the wake of a cold front. The best chc for additional showers/TSRA overnight will be INVOF KIPT through about 07Z Wed. Increasing NW sfc wind during the mid to late morning hours Wednesday will average 8-10 kts with gusts into the upper teens to lower 20 kt range beginning 14-15Z Wednesday, and continuing throughout the afternoon hours. The cold frontal passage is timed to occur across the Lower Susq Valley around or shortly before daybreak Wednesday, after which any low clouds will gradually lift and clear out substantially by the early afternoon INVOF KIPT...KMDT and KLNS. Mainly VFR is expected up to a few hours earlier (i.e. Late Wed morning) across the NW and Central Mtns. NW winds will gust into the upper teens to lower 20 KT range during the late morning and afternoon hours Wed. Outlook... Wed...AM MVFR/IFR becoming widespread VFR by mid day. Thu-Fri...VFR/No sig wx expected. Sat-Sun...Warm and humid mainly VFR with scattered showers/thunderstorms. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald/La Corte LONG TERM...Ross AVIATION...Lambert

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