textproduct: State College

WHAT HAS CHANGED

* SPC introduced level 1/5 severe t-storm risk for Thursday

KEY MESSAGES

1) Fall-like pattern into midweek reverts to warmer, more humid/typical late summer conditions to close out August

2) Scattered strong to severe thunderstorms with locally heavy rain are possible Thursday afternoon

DISCUSSION

KEY MESSAGE 1: Fall-like pattern into midweek reverts to warmer, more humid/typical late summer conditions to close out August

One more Fall-like day with cooler-than-average daytime highs as the upper level trough starts to lift out of the area. We still can't rule out a spotty, quickly passing light rain shower or brief sprinkles mainly over the higher terrain north/west of I99 and north of I80 through the afternoon. Relatively cool, cyclonic/northwest flow aloft will continue to generate clouds downwind of Lake Erie and therefore will hedge sky cover upward vs. guidance.

Clearing skies tonight will favor fog formation into Wednesday morning especially in the valleys as the ground remains rather moist from recent rainfall. Warmer on Wednesday with more sunshine and highs +5-10F higher vs. Tuesday.

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KEY MESSAGE 2: Scattered strong to severe thunderstorms with locally heavy rain are possible Thursday afternoon

*SPC introduced level 1/5 severe t-storm risk for Thursday

A broad mid-level trough will continue to shift eastward toward the Northeast on Thursday. A weak surface low will move across Quebec with a cold front extending southward into the eastern Great Lakes. Moderate instability is forecast in advance of the front with broad ascent supporting storm development. Multicell clusters capable of damaging winds, and perhaps isolated large hail, are expected. A more focused region of greater potential may exist from central Pennsylvania into eastern New York. The potential for cloud cover across the region casts some uncertainty and therefore, confidence was not high enough for a Slight Risk (level 2/5) at this time. WPC continues to highlight the eastern half of the forecast area with a level 1/marginal risk excessive rain outlook with PWATs fcst to climb to 1.5 inches in advance of the aforementioned cold front.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

An upper level low over southwestern Ontario will keep a cyclonic flow of cool air across the Great Lakes into Tuesday.

BFD will likely bounce between IFR and MVFR to begin the day before MVFR is favored for the remainder of the morning. MVFR/low VFR ceilings building into JST in the morning as a stratocumulus deck builds southward. This may also lead to a few hours of late morning/early afternoon high MVFR/low VFR ceilings at UNV and IPT. Tuesday afternoon could see some gusty winds again, current thinking in the 15-20 knots at times, most likely in the early to mid- afternoon, along with an increase in VFR stratocumulus.

Isolated showers are possible in the northern tier, but coverage and intensity is expected to be low. Confidence is low (<10%) prevailing impacts will occur at any airfield. Skies will gradually clear out later Tuesday afternoon into the evening , as the upper low pivots out to the northeast. This gives way to clearer skies Tuesday night and calm winds into Wednesday morning. Early indications are patchy morning fog building in Wednesday morning with signal strongest in the northern airfields.

Outlook...

Wed...Patchy morning fog, otherwise mainly VFR conditions.

Thu...Restrictions possible in scattered afternoon showers and storms.

Fri...Still a slight chance of a shower, VFR otherwise.

Sat...Clearing conditions, VFR favored.

CTP WATCHES/WARNINGS/ADVISORIES

None.