Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 140008 AFDCTP Area Forecast Discussion National Weather Service State College PA 808 PM EDT Thu Aug 13 2020 .SYNOPSIS... A stationary frontal zone wavering over southern PA will maintain a chance of scattered, locally heavy downpours tonight into Friday. Unsettled conditions with cooler temperatures are forecast for the upcoming weekend. && .NEAR TERM /UNTIL 7 AM FRIDAY MORNING/... Quick update for cancellation of flash flood watch for York and Lancaster Counties. Previous discussion 736 PM EDT... Moist/unstable airmass with sfc dewpoints in the 65-70F range resides across the southern tier of CPA. 23UTC SPC mesoanalysis shows zone of 500-1000 J/kg of MLCAPE helping to fuel isolated downpours. The loss of heating should fade the convection with POPs trending lower into tonight. Latest CAMs support the bearish trend. Quite an airmass change heading into the northern 1/2 of the CWA with a mainly clear sky and comfy dewpoints in the low-mid 50s. Odds are increasing that the flash flood watch may be able to expire before 04Z expiration. Will coordinate with PHI/LWX. Low dewpoint air will allow min temps to dip into the 50s across the northern tier, creating a favorable setup for radiational valley fog with air/water temps exceeding 20F. Temps stay muggy across the south central/southeast zones with lows around 70F in the lower Susquehanna Valley metro areas. && .SHORT TERM /7 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... A repeat of today is in store for Friday with sct/nmrs storms again forming mainly in the aftn. One change may be that the storms may actually creep more to the north on Friday with an upper level trough developing in the OH Valley. Maxes look very very similar to today, as well. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... By Friday evening, split flow produces a weak broad upper trough over the lingering frontal boundary to our south. This will bring a surge of moisture into the Commonwealth Saturday afternoon and Sunday. Anomalous southeasterly 850-mb flow (approaching record values for this time of year) will help funnel ample moisture into the Middle Atlantic. Have upped PoPs in the SW starting Saturday afternoon and maintain higher PoPs farther east through Sunday evening. Despite the GFS being the outlier earlier in the week, other models have gradually trended toward a wetter solution. Still, ample uncertainty remains. The NAM brings almost no rain to north of the Mason-Dixon line Saturday and Sunday, while the GEFS mean sits at widespread storm total precip exceeding 1" and spotty 2" amounts across south central PA. Opted to ramp up PoPs across south-central PA where confidence is highest in rain occurring, but shaved off about 20% of QPF from a blend of NBM, WPC Guidance, and the SuperBlend. The weak surface trough will stick around through Monday before a cold front sweeps through the Commonwealth, marking the end of an unsettled stretch and ushering in cooler and drier weather. The Climate Prediction Center 6-10 temperature outlook favors below normal temperatures in central PA. This will be a welcome relief after a prolonged stretch of warm weather. Additionally, the arrival of high pressure by the middle of next week seems to favor a drier than normal stretch for a little bit. Precipitation chances ramp up again across the southern tier by late week, but no significant impacts are expected. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... 00Z TAFS sent. Isolated showers and storms across the south, but not near any TAF sites at this point. Some fog and lower clouds possible late, but rainfall less widespread today than in recent days, thus I did not hit fog and low clouds very hard. Friday at this point looks mainly dry, similar to what we had today, thus only used VCSH across the south. More in the way of widespread showers possible for later Saturday into Sunday Night, but still a ways out. Much of our area could remain between systems to the southeast and southwest of our area. Outlook... Sat-Sun...More in the way of widespread showers possible. Mon...Still a chance of showers and storms. Tue...Clearing skies. && .CLIMATE... A daily record high temperature of 87 degrees was tied at Bradford on 8/13. The previous record was set in 1988. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Steinbugl NEAR TERM...Steinbugl SHORT TERM...Lambert/Dangelo LONG TERM...RXR/Banghoff AVIATION...Martin CLIMATE...Gutierrez

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