263 FXUS61 KCTP 032304 AFDCTPArea Forecast Discussion National Weather Service State College PA 704 PM EDT Fri Oct 3 2025
.SYNOPSIS... * Dry with well-above average temperatures this weekend and into the beginning of next week. * Cold frontal passage brings showers on Tuesday/Wednesday. * Dry conditions again later next week with low temperatures approaching the freezing mark.
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.NEAR TERM /THROUGH SATURDAY/... Clouds (tiny cu NW and SE and high clouds S) should dissipate and slide away before or around sunset. Wind goes calm and stays that way. Fog is then expected to form in the valleys, not widespread, but more than Fri AM. The West Br and tribs to it have the best chc of having fog overnight. Temps should stay just 3-5F milder than the prev night but dewpoints will also be a notch higher. Coldest spots will dip to around 40F, and most will be 45-50F.
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.SHORT TERM /SATURDAY NIGHT THROUGH 6 PM SATURDAY/... WYSIWYG. More of the same Sat. After fog goes away: sunny and very warm for Oct. 8H temps of +12-15C will mix down to hit 80F over half the land mass of Central PA. Those are more like late June or early Aug highs. The higher elevations stay below that mark. Records are generally 5+F greater than the forecast highs, though. GFS is much weaker with the inversion than NAM. The weak inversion is a good signal for a dewpoint bomb/drop during the day. But, without support from NAM and HREF mean, don`t want to go too wild with a departure from guidance. But, did nudge mid- day/aftn dewpoints down a few degs from NBM, esp in the mtns and Lower Susq.
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.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... The dry pattern throughout the short-term forecast period appears to trend wetter with the approach of a surface low pressure from the central US, which will track northeastward into Ontario. The low will drag a cold front through the area in the Tuesday/Wednesday timeframe, bringing some beneficial rainfall to central Pennsylvania.
While there should be decent moisture return ahead of the front, with PWAT values rising to the 1.25-1.4 inch range (~90th percentile for this time of year), there is still some uncertainty as to just how much rain will fall. Ensemble mean QPF is generally around 0.3 inches in northwest PA, with lesser amounts as you move south and east, but some of the deterministic guidance, namely the 12Z GFS, continues to show the potential for upwards of an inch of rain over parts of central PA. This does not appear to be the most likely solution at this point, however, as most guidance shows the best synoptic scale forcing passing well to our north. Additionally, weak instability should help to limit rainfall rates.
All guidance shows high pressure building into the region at the surface and aloft in the wake of the cold front. This setup would allow for another spell of dry weather into the latter half of the week. With a 1030 mb surface high expected to be centered over the region Wednesday and Thursday nights, ideal radiational cooling conditions are anticipated with mainly clear skies and light winds. Temperatures will fall into the 30s and 40s both nights and frost formation is likely over the north and west. There is also some potential for temperatures to drop below freezing Wednesday night across the northern tier.
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.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... Looking at clear skies overnight into Saturday, as high pressure remains over the area. The combination of light winds, low PW values, and clear skies may result in a little fog in spots, but the airmass is quite dry, so any fog will be limited.
For the 00Z TAF package, went close to what the 18Z package with regard to the location and timing of the fog.
Earlier discussion below.
Expect fog to form in the valleys, likely more widespread than Fri AM. Have mentioned IFR fog for a few hours at IPT (most likely) and AOO, but UNV has much lower chc (20%) of dipping to IFR. Still mentioned it there, though. BFD may get a little fog in the late evening/early night, but probably go back to VFR for the balance of the night as the coldest air slides off into the deep valleys nearby. Sat will be VFR after the fog (and any little bit of low stratus near the fog) dissipates. The center of the sfc high will be close enough to keep the wind very light and out of the S/SW again. More of the same for Sun and Mon.
Outlook...
Sun-Mon...AM Fog (Mainly N PA); otherwise VFR. Tue...Sct SHRA. Tue PM...CFROPA. SHRA. TSRA poss. IFR fog poss mainly NW. Wed...Sct AM SHRA SE. Otherwise becoming VFR.
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.CTP WATCHES/WARNINGS/ADVISORIES... None.
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SYNOPSIS...Dangelo/NPB NEAR TERM...Dangelo SHORT TERM...Dangelo LONG TERM...Bauco/NPB AVIATION...Dangelo/Martin
NWS CTP Office Area Forecast Discussion