487 FXUS61 KCTP 260033 AFDCTPArea Forecast Discussion National Weather Service State College PA 833 PM EDT Thu Sep 25 2025
.SYNOPSIS... * Drying out and not as humid on Friday * Above average temperatures forecast through the end of September * Considerable uncertainty in potential rainfall/tropical moisture next week
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.NEAR TERM /THROUGH 6AM FRIDAY/... Steady rainfall along a cold front has exited east of the area this evening, with scattered clouds and some isolated showers across the region. A weak cold front will move to the east of the CWA in the middle of the night, and some drying is expected. Little to no precip is expected past midnight. Clouds and a light wrly wind could thwart fog formation, so we haven`t included mentions for tonight at this point. Temps get into the 50s for the NW half of the CWA, but stick in the m60s in Lancaster/Harrisburg/York.
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.SHORT TERM /FRIDAY AND FRIDAY NIGHT/... The westerly flow across LE and passage of the upper trough should cause isolated SHRA over far nrn PA on Friday. However, most of the CWA will be dry with lower dewpoints/humidity and subsidence. GFS has a little more vigorous upper trough as it pushes thru Central PA, and generates a few aftn SHRA. But, most guidance is dry keeping vertical depth of convection shorter. Temps will be similar to Thursday despite weak cold advection.
Fri night will hold a better chance for fog - if it stays clear after an initial period of clearing early in the night. Guidance does deepen an upper low over the TN valley off the remnants of the upper trough that will have passed thru PA. That could draw moisture/clouds into the state from the south later Friday night.
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.LONG TERM /SATURDAY THROUGH THURSDAY/... Newest wrinkle to the forecast for the weekend is that the upper low lingers to our west for a little while and could draw enough moisture north into southern PA to cause a few -SHRA or patches of -RA on Sat and Sunday. PoPs have increased slightly from past runs, but we`ve confined them to locations S of I-80 for the time being. Some uncertainty exists in regard to the possibility of tropical moisture being drawn into the state as a complicated interaction is expected between the tropical cyclone(s) off the coast and our old upper low. At this point, the cyclone(s) themselves are not expected to cause any direct impacts to Central PA. But, due to the uncertainty with the extent and position of any tropical moisture plume, very low PoPs linger into Tuesday across the far S. The forecast then gets dry for the middle of next week (high confidence) as sprawling high pressure drops down from Canada.
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.AVIATION /00Z FRIDAY THROUGH TUESDAY/... Now that the cold front has cleared the area, VFR conditions prevail at all all airfields. Overnight, some clearing could support patchy fog while northwest/upslope flow supports low clouds. Highest confidence in IFR/LIFR at BFD and JST, with IFR possible at IPT, UNV, and AOO. MDT and LNS should maintain VFR ceilings for most of the night, but there is a low chance (
NWS CTP Office Area Forecast Discussion