Area Forecast Discussion
Issued by NWS State College, PA

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937 FXUS61 KCTP 220142 AFDCTP Area Forecast Discussion National Weather Service State College PA 942 PM EDT Mon May 21 2018 .SYNOPSIS...
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Low pressure over the upper midwest will track across the eastern Great Lakes tonight and Tuesday, pushing an attendant warm front into Pennsylvania. A trailing cold front will then sag southeast across the Commonwealth Tuesday night. High pressure will build southeast into the region for the second half of the week.
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&& .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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An approaching warm front will bring an increasing chance of rain and possible embedded thunderstorms back into central PA later tonight. Latest model guidance supports near 100 pct POPs across the northwest counties, as nose of low level jet pushes through this part of the state roughly between 04Z-09Z. Will maintain lower POPs of around 50 pct across the southeast portion of the forecast area. Although the warm front should remain west of the forecast area tonight, models do indicate a fair amount of elevated instability, mainly across the Allegheny Plateau. Thus, will include mention of thunder late tonight, especially over the western counties. Increasing cloud cover ahead of approaching warm front will help to hold temperatures up tonight with expected minimums in the upper 50s and low 60s most places.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
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A southwesterly low level jet and associated plume of anomalous PWATs will be overrunning the western Pa warm front early in the day, resulting in a rainy morning across central Pa. Low level stability forecasts suggest the warm front, which will begin the day hung up along the west slopes of the Alleghenies, will work into the central mountains during the afternoon, while stable air and low level southeast flow remains entrenched across the eastern portion of the forecast area. Expect rain to taper off over the region during the afternoon, as weakening low level jet shifts southeast of the area. Focus for the afternoon will be on potential of severe weather developing in warm sector across the western half of the state. Overcast skies should give way to breaks of sunshine west of the warm front during the afternoon, leading to moderate instability per 18Z model guidance. Large scale forcing ahead of approaching shortwave over the Grt Lks and favorable jet dynamics beneath right entrance region will enhance the convective potential. 0-6km shear in the 40-45kt range will likely support organized bands of convection and possible supercells across the western counties. Cloud cover through at least the first half of the day will hold temperatures down, although humidity will become noticeable as dewpoints push back into the 60s. Superblend/NBM indicate highs Tuesday will range from the low to mid 70s over much of the forecast area, with readings possibly stuck in the 60s east of the Susquehanna River.
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&& .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
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A trailing cold front will sag south across the region Tuesday night, accompanied by dwindling convection. Look for high pressure and dry weather Wednesday 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. A more unsettled, humid and a little cooler weather is likely by the end of the weekend and on Memorial Day. While there will be pops in the forecast, still uncertain exactly how wet things will turn out.
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&& .AVIATION /01Z TUESDAY THROUGH SATURDAY/... VFR conditions exist across all of Central Pennsylvania this evening, although high clouds from approaching convection already overspreading from the west. A warm front will begin to push north overnight bringing widespread showers with embedded thunderstorms, along with deteriorating flying conditions. Look for MVFR/IFR to develop overnight. Tuesday will start with widespread rain/showers and even some embedded thunderstorms, along with associated MVFR/IFR conditions. Some slow improvement possible later Tuesday, with a cold front crossing the region. However, the cold front may trigger a gusty thunderstorm or two. Outlook... Wed...AM MVFR/IFR cigs wrn 1/3. Thu-Fri...VFR/No sig wx expected. Sat...Mainly VFR with scattered showers/thunderstorms. && .CLIMATE... Some perspective on the recent wet pattern... Total rainfall during the past 1 & 2 week periods ending on 5/19 ranked as the WETTEST on record at Harrisburg. Also through 5/19, the 5.28 inches of total rainfall ranks as the 3rd wettest month-to-date period. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Fitzgerald/La Corte NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald/La Corte LONG TERM...Ross AVIATION...La Corte CLIMATE...

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