textproduct: State College

WHAT HAS CHANGED

* Dense Fog Advisory in effect until 9AM for Warren, McKean, and Elk County

KEY MESSAGES

1) Patchy dense fog this morning gives way to a mostly sunny and dry day.

2) An unsettled but not particularly wet period is expected mid to late week.

DISCUSSION

KEY MESSAGE 1: Patchy dense fog this morning gives way to a mostly sunny and dry day.

Dewpoints are still in the mid 60s to low 70s this morning. Mostly clear skies and light winds have resulted in thick fog in the typical valley locations across northwest PA. The valley fog is accompanied by some low stratus in the northwest mountains, which is dropping visibility to a quarter mile or less across much of Warren, McKean, and Elk County. As such, we hoisted a Dense Fog Advisory there until 9AM.

With weak high pressure building over the region today, fog will eventually mix out giving way to a very nice day. Dewpoints will drop through the afternoon providing some relief from the humidity. Scattered fair weather cumulus clouds will align northwest to southeast along horizontal convective rolls this afternoon before fading tonight with the loss of daytime heating.

Lowering dewpoints tonight and an expectation of rain-free conditions all day should make the chance for fog considerably lower tonight. There could still be some patchy fog in the deepest valleys, but most locations should stay cloud-free.

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KEY MESSAGE 2: An unsettled but not particularly wet period is expected mid to late week.

A short wave trough rotating around the base of the deep upper low over Hudson & James Bays will be the next help to lift and destabilize the air over PA by Wednesday. Expect some showers to impinge upon Warren Co in the aftn on Wed and spread along the NY border. Some of them could advance another county to the south before daylight wanes and they die off. Precip chcs Wed night and Thurs AM now look a little lower than previous forecasts. But, isolated showers are still possible then. Heights do dip for real on Thursday/night and will probably develop a weak low pressure system to our south. That low will push east to the sea Friday. Some light to moderate rain should overrun the boundary to our south and make the southern half of the CWA wet - but not too wet - on Thurs night and early Friday. Model agreement lowers for the weekend, clouding the crystal ball. PoPs end up at 40-50% Sat and Sun without confidence in the forecast being either wet or dry.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

Fog and low clouds will gradually dissipate through the morning, with VFR conditions expected area-wide by 15Z. Expect scattered clouds around 5000 feet for much of the day with northwest winds at 5 to 10 knots. Fog appears much less likely tonight with a drier airmass in place, and VFR conditions are favored at all TAF sites through the end of the TAF period.

Outlook...

Wed... VFR conditions with restrictions from afternoon SHRA/TSRA possible in the northwest early.

Thu... Afternoon SHRA/TSRA with brief restrictions possible. Otherwise, VFR conditions.

Fri...Chance of SHRA across the south, restrictions possible, otherwise dry.

Sat...Chance of SHRA statewide, restrictions possible.

CTP WATCHES/WARNINGS/ADVISORIES

Dense Fog Advisory until 9 AM EDT this morning for PAZ004-005- 010.