226 FXUS61 KCTP 271826 AFDCTPArea Forecast Discussion National Weather Service State College PA 226 PM EDT Sat Sep 27 2025
.SYNOPSIS... * Increasing clouds today with light rain most likely south of the Turnpike/east of I-81 this afternoon into early tonight * Partly to mostly sunny and very warm to close out the final weekend of September; start of another extended dry spell * Mild/warm start early next week before turning seasonably cooler with stretch of dry weather continuing into October
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.NEAR TERM /THROUGH TONIGHT/... A check of surface observations and webcams show the steady light rain generally covering southern PA along and south of the turnpike. Over southern Somerset county, precipitation enhanced by a southeast flow has allowed for 0.50 to 1.00" to fall in this area. Six hour FFG is around 2.00".
Expect the area of light rain to slowly move north through the day with sprinkles or isolated showers toward I-80.
Hires data shows rain exiting southeast PA by 12Z Sunday as high pressure starts to move in from the Great Lakes. Clearing from west to east along with residual moisture and light/calm wind will promote fog formation which may become locally dense and significantly reduce the visibility during the predawn/post sunrise period.
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.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AM fog will give way to partly/mostly sunny and very warm conditions to close out the final weekend of September on Sunday. Max temps fcst in the 75-85F range are 10 to 20 degrees above the historical average for late September. High pressure settling over CPA Sunday night favors more radiational fog into early Monday morning.
Monday also will be quite warm by end of September standards with fcst highs very close to/a few degrees cooler vs. Sunday. High pressure continues to dominate the pattern, setting up what should be an extended period of dry weather through next week.
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.LONG TERM /TUESDAY THROUGH FRIDAY/... Confidence is now increasing in an extended period of dry wx for next week. This is due to better model agreement in the evolving blocking pattern, showing the area remaining under the influence of high pressure both at the sfc and aloft Tue-Fri.
Backdoor cold front will allow seasonably cooler/chilly air to filter into the area to start October as 1030+mb Canadian high moves southeast from Hudson/James Bay into New England. This airmass change will drop daytime max temps by 5-10F day/day Wed & Thu and increase the risk of late night/early AM frost particularly in the northern tier where NBM min temps are fcst in the mid 30s.
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.AVIATION /18Z SATURDAY THROUGH THURSDAY/... Accounted for -SHRA over southern PA either in the body of the forecast, or a PROB30 where confidence is lower (
NWS CTP Office Area Forecast Discussion