Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 230135 AFDCTP Area Forecast Discussion National Weather Service State College PA 935 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/...
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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.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
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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.
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&& .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 /00Z WEDNESDAY THROUGH SUNDAY/... MVFR and localized IFR Cigs will continue through at least the first half of tonight (perhaps until shortly after sunrise Wed) across the region near, and to the east of the Susquehanna Valley under light easterly llvl flow near the sfc. Mainly VFR will dominate elsewhere, with isolated to sctd generally brief MVFR cigs and vsbys in SHRA/TSRA along and ahead of a cold front that`s currently pushing SE across Lake Erie. The SHRA and TSRA will weaken substantially across the eastern half of PA as they encounter the cooler and more stable air. As the NW breeze develops in the wake of the cold front, there could a several hour (or longer) period of low cigs from moist upslope flow (03-12Z Wed) prior to more significant drying advecting into the area and enhanced by deeper vertical mixing beginning later Wednesday morning. 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 with clearing out substantially by the early afternoon INVOF KIPT...KMDT and KLNS. Mainly VFR is expected a few to several 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...La Corte/Lambert

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