textproduct: State College

WHAT HAS CHANGED

Small uptick the potential for isolated flooding and stronger storms on Thursday afternoon.

KEY MESSAGES

1) Seasonable with some showers through midweek followed by more unsettled and cooler conditions over the weekend

DISCUSSION

KEY MESSAGE 1: Seasonable with some showers through midweek followed by more unsettled and cooler conditions over the weekend

Crumbling cu into tonight setting up some valley fog formation into early Wednesday morning. Cold front crossing Lake Erie should be accompanied by rain showers into the northwest Alleghenies this morning. The front may touch off some additional showers/isolated t-storm across the northwest 1/2 of the forecast area through the afternoon. Another period of rain should be focused across the southern portion of the CWA on Thursday with some locally heavy downpours possible. The latest D2 WPC Excessive Rainfall Outlook brings the Marginal Risk (level 1 out of 4) north of I-80, though the best chance for heavy rain appears to be in southeast PA and NJ. Recent model runs have also trended slower with the arrival of a front on Thursday, resulting in an uptick in severe weather chances. SPC introduced a Marginal Risk in southeast PA with damaging winds as the primary threat, though veering low level winds could result in a sneaky tornado threat as well.

Friday looks like a very nice day with mostly sunny skies, dry weather, and relatively lower humidity. Then an upper trough carving out over the Great Lakes will bring increasingly unsettled weather conditions over the weekend. There is still considerable uncertainty with timing, intensity, and coverage of storms, but it shouldn't be a washout by any stretch. This system will also deliver some relatively cooler air both at the surface and aloft. This setup could prove favorable for clusters of gusty t-storms with small hail. The troughing pattern holds on into next week which favors temps near to slightly below the historical average for late August.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

Patchy fog has formed in the valleys of north-central PA and has led to the development of LIFR ceilings at IPT over the last few hours while all other TAF sites remain VFR. Expect fog and low clouds to dissipate by 15Z.

A shortwave moving overhead today will bring the chance for a few showers and possibly a thunderstorm to the region along its associated cold front. The weak front will have relatively little moisture to work with for this time of year, so showers are expected to remain isolated to scattered at best. BFD has the highest chance for seeing rain, so the PROB30 has been maintained there. Some guidance suggests that some rain could make it to JST and UNV as well, but confidence in coverage is too low to mention the potential in the TAFs for now. Winds during the day tomorrow will be out of the west at 5 to 10 knots with a few gusts to 15 knots possible, especially at BFD and JST.

Chances for fog are slightly higher tonight as low-level moisture begins to increase ahead of a more energetic shortwave trough that will move through for Thursday. Increasing mid and high clouds ahead of this feature may mitigate the fog threat somewhat, but the signal appears to be strong enough to include visibility and ceiling restrictions at most TAF sites with the exception of MDT and LNS. Showers and a few thunderstorms associated with this disturbance will begin moving in from the west after 06Z.

Outlook...

Thu...Periods of showers and thunderstorms focused across the southern half of central PA.

Fri...AM fog, otherwise trending VFR.

Sat-Sun...Scattered to numerous showers/t-storms likely especially on Sunday.

CTP WATCHES/WARNINGS/ADVISORIES

None.