textproduct: State College

WHAT HAS CHANGED

Adjusted POPS up for Central and Southern PA today by about 20 percent from NBM guidance.

KEY MESSAGES

1) Unseasonably deep upper low over the Upper Great Lakes today will move Southeast to Lake Ontario by Monday morning bringing another few rounds of showers and thunderstorms, mainly across Northern PA this afternoon and evening.

DISCUSSION

KEY MESSAGE 1: Unseasonably deep upper low over the Upper Great Lakes today will move Southeast to Lake Ontario by Monday morning bringing another few rounds of showers and thunderstorms, mainly across Northern PA this afternoon and evening.

A subtle shortwave trough rotating around the southeast side of the upper low will spark some afternoon/evening showers and TSRA today, followed by only a brief downtrend in convection before a well-defined trough moves SE with its axis near the PA/OH border by shortly after midnight tonight.

HREF and SREF MUCAPEs will top out between 750-1000 j/kg with wet bulb zero levels descending about 3-4 KFT to only around 6 KFT AGL across the Northern Mtns this afternoon and tonight. It's almost a slam dunk to see some periods of significant small hail from the stronger low-topped TSRA between 18Z Sun and 00Z Monday across the NW and maybe the Central/Ncent Mtns. SPC has a marginal risk of SVR TSRA for today across all of the CWA except for the southern tier layer of counties. Coincidentally, NBM POPS had to be raised by at least 20 percent (to agree with the SPC outlook) across the Central and Scent Mtns along with much of the Middle and Lower Susq Valley where a relative min of zero to 10 POPs was noted.

Luckily, this second and more potent upper trough will be pivoting over the Commonwealth overnight tonight with MUCAPE of only a few hundred J/KG, supporting mainly showers and perhaps a low-topped TSRA or two moving inland from the warm waters of Lake Erie.

Maxes only in the 60s and a brisk W wind across the northern and western mtns will make it feel much more like Sept/Oct than mid- Aug. Valley locations will see more sun preceding any convection with high temps reaching the mid 70s to near 80F in the Lower Susq Valley.

Similar conditions are expected for Monday with the center of the upper low still hanging around our longitude and only moving slowly poleward. The SHRA/TSRA will likely be confined to only the nrn tier of counties in PA on Monday.

AVIATION /13Z SUNDAY THROUGH THURSDAY/

Mid morning update.

Adjusted the current TAFS for current obs and also small clusters of showers and isolated storms.

Earlier discussion below.

MVFR will predominate most airfields through the mid morning hours with pockets of lower IFR ceilings due to upslope flow at KBFD and KJST. We'll see a transition with varying VFR and MVFR in SHRA/Isolated low-topped TSRA focused in the 19-23Z window. Westerly wind gusts of 25+ Kts and small hail (GS) are possible across the northern Mtns of PA including KBFD.

Cooling temperatures aloft and a 20+kt 850mb westerly jet should allow for moderately gusty winds for the late morning and afternoon hours.

Outlook...

Mon-Wed...Patchy morning fog, otherwise mainly VFR conditions return early next week with lower statewide precipitation chances.

Thu...Chance of showers and storms again.

CTP WATCHES/WARNINGS/ADVISORIES

None.