textproduct: State College

WHAT HAS CHANGED

No significant changes to the current forecast.

KEY MESSAGES

1) Mainly dry conditions with variable amounts of high based stratocu and altocu clouds will persist through Saturday with any precipitation chances confined to the southern tier of the state.

2) Sunday will bring a return to wet conditions with showers and thunderstorm chances returning.

DISCUSSION

KEY MESSAGE 1: Mainly dry conditions with variable amounts of high based stratocu and altocu clouds will persist through Saturday with any precipitation chances confined to the southern tier of the state.

A northwesterly upper level jet core will extend from southern Ontario to the New England Coast. As the right entrance region of this jet drifts over western and southern Pennsylvania this afternoon it will interact with a remnant MCV from convection that is currently ongoing across Illinois and Indiana.

This area of more focused ascent should lead to another round of clouds and some shower development in the southern tier of the state later today.

Main timing looks to be from the late morning to mid-afternoon. The ascent may allow for some spotty afternoon showers elsewhere, but dry air filtering in from the north should keep things fairly isolated.

In the wake of upper level features, drier air filters in from the north and skies should start clearing this evening into Saturday. Noticeably less humid conditions will accompany the start of the weekend with any isolated rain chances looking to remain in the southwest.

KEY MESSAGE 2: Sunday will bring a return to wet conditions with showers and thunderstorm chances returning.

A low pressure system moving through Canada will allow a stalled frontal boundary to move through Pennsylvania as a warm front on Sunday. This will bring a moist airmass, with PWATs possibly exceeding 2" into Pennsylvania. With a secondary low likely forming closer to Pennsylvania at the intersection of the warm front and a trailing cold front, this will invigorate development of showers and thunderstorms. With a cold front draping across Pennsylvania Sunday night, multiple rounds of showers/thunderstorms may be possible into the night.

As it stands right now, ensemble guidance has the northern tier of Pennsylvania targeted for highest rain probabilities and totals. Exact timing of this activity and how fast/slow the cold front moves through will likely become clearer as we approach Sunday. With such high PWATs and potential for multiple rounds/training activity, flooding potential will need to be watched. Should the cold front stall/move slower, activity may linger into Monday morning. After that passage, the start of next week is showing signs of high pressure moving over the region.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

Patchy morning fog and low stratus (AOB 500 ft AGL) will mix out soon after sunrise today, with VFR favored & light winds of ~5 kts through the rest of the TAF period. Intermittent MVFR ceilings are possible this morning and early afternoon, primarily at KJST/KAOO, as diurnal/upslope cumulus develop.

Some showers and maybe even a rumble of thunder will move into the Laurel Highlands (mainly Somerset County) for late this morning with up to a few tenths of an inch of rain likely as the northern edge of an original Midwest MCS slides across that part of the stat.

The latter half of this 12Z TAF period will feature high pressure nosing in from Canada with a weak backdoor cold front moving into Central and Northern PA. A northeasterly wind shift is expected behind the front, which could reach KBFD/KIPT around or after 00Z Saturday.

Winds may gust to around 15 kts with the frontal passage, primarily if it moves through during the evening before the boundary layer stabilizes, with lower wind gusts (5-10 kts) if it moves through later into the night.

Outlook...

Sat...AM fog possible, then VFR. Warm front moves in and SHRA/TSRA likely W Sat night.

Sun...Restrictions possible in showers/thunderstorms.

Mon...CFROPA by Monday morning. SHRA/TSRA ending Mon AM. Mainly VFR for most of the day.

Tue...Mainly dry.

CTP WATCHES/WARNINGS/ADVISORIES

None.