Area Forecast Discussion
Issued by NWS State College, PA

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041 FXUS61 KCTP 081810 AFDCTP Area Forecast Discussion National Weather Service State College PA 210 PM EDT Tue Jul 8 2025 .SYNOPSIS... * Flash flooding and damaging thunderstorm wind risk this afternoon and evening across the southeastern portion of central PA * Similar setup for Wednesday with renewed damaging wind and flash flooding risks focused over southeast PA * Continued seasonably warm and humid with scattered afternoon and evening thunderstorms through the weekend && .NEAR TERM /THROUGH TONIGHT/... Thunderstorms are beginning to develop early this afternoon along and ahead of an outflow boundary associated with morning convection that has moved in from the Ohio Valley. As this convection moves eastward with time through the afternoon, it will encounter a more unstable and sheared airmass, likely helping it to take on a more linear mode. With this evolution, the likelihood of damaging wind gusts will increase. Pwats eclipsing 2" over southeast PA will support a flash flood threat where any tstms train. We issued a flood watch starting 18Z today for a portion of the Lower Susquehanna Valley in coordination with WFO LWX. In addition to the robust and anomalous pwat values, very efficient warm-rain processes could lead to rain rates >2"/hr at times resulting in potential instances of flash flooding. Ahead of the rain, there also remains some concern for max HX values to reach or exceed the century mark in parts of the LSV. However, not thinking that this will be widespread enough to warrant a Heat Advisory. Hires models show the majority of showers/storms will shift to the east before midnight (in fact, most guidance has the bulk of the convective activity winding down before 8 PM). Min temps will be a bit cooler than last night, with fog likely forming in the valleys through the predawn hours Wednesday. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... Similar overall synoptic setup on Wednesday & Thursday with gradual southward shift to the severe t-storm and FF risk areas coincident with zone of max PW. Conditions will remain humid and with daytime highs in the 80s. && .LONG TERM /FRIDAY THROUGH MONDAY/... The forecast for Friday and the weekend is more uncertain, with some guidance suggesting a break in the unsettled pattern, and others suggesting active weather continues. An active pattern would favor continue heat/humidity while a quieter pattern could support the intrusion of lower dewpoints and more refreshing conditions. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/...
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Thunderstorms ahead of a slow-moving cold front will continue to impact the central Pennsylvania airspace over the next couple of hours, with highest confidence in impacts along a north- south line extending from UNV to HGR and areas east. Thunderstorms will bring about localized drops in visibility with heavy rainfall and frequent lightning near UNV from 18Z-20Z Tue, MDT/LNS between 19Z-23Z Tue, with lower probabilities of thunderstorm impacts at airfields at AOO (closer to cold front; however, non-zero chance from 18Z-19Z) and IPT (best instability further south; however, non-zero chance between 19Z-21Z). The most recent guidance does show fair agreement in thunderstorm potential; however, main difference in timing with regards to precipitation as the cold front continues to progress eastward this evening. In the wake of the cold front, areas that have received locally heavy rainfall this evening will have higher potential for fog and widespread visibility restrictions overnight. At this time, have progged AOO/UNV towards LIFR conditions overnight; however, model guidance indicates some potential at all airfields except for MDT/LNS. Have stuck with guidance trends; however, will have to continue to monitor trends at MDT/LNS with heavy rainfall and fog potential overnight. After sunrise on Wednesday (12Z Wed - 18Z Wed), model guidance shows fair agreement with respect to restrictions being lifted by 12Z for most airfields. The 18Z TAF package does set the goal post slightly wider, with widespread restrictions lifting closer to 13-14Z give some lingering low-level moisture in RAP model soundings. Outlook... Wed...Best chance for storms and restrictions in southern PA. Thu-Sun...Potential for showers and thunderstorms, mainly aftn/eve.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... Flood Watch until midnight EDT tonight for PAZ057-059-065-066. && $$ SYNOPSIS...Steinbugl/Colbert NEAR TERM...Steinbugl/Colbert SHORT TERM...Steinbugl/Colbert LONG TERM...Lambert/Colbert AVIATION...NPB