textproduct: State College

WHAT HAS CHANGED

* No significant changes to the forecast at this time

KEY MESSAGES

1) A rain-free weekend is on tap

2) Late summer warmth is still slated to end the month of August and start September next week, with severe weather and heavy rain threats also present

DISCUSSION

KEY MESSAGE 1: As a frontal boundary continues to slowly sink southward into the southern Mid-Atlantic this weekend, a ridge of high pressure will become our dominant weather feature. This will mean partly-mostly sunny days and mainly clear nights through Sunday. Given our recent wet stretch of weather and abundant soil moisture in many areas, late night and early morning fog will be common, particularly in the river valleys of northwest and north-central PA.

Temperatures/humidity levels will be seasonable and comfortable through Saturday. On Sunday, as low-level winds begin to switch into a more southerly direction, afternoon temperatures and humidity levels will start to creep upward.

KEY MESSAGE 2: During next week, there is good agreement amongst our various ensemble prediction systems that an expansive summer-time ridge axis at upper levels of the atmosphere will flex its muscle and expand northeastward from the southern states and middle of the CONUS.

There are two primary consequences for the sensible weather across the Commonwealth as a result of the above mentioned scenario. First, very warm and increasingly humid weather will settle in, even as we flip the calendar to September. Second, as a northwest flow aloft develops over much of the Mid-Atlantic and Northeast with embedded disturbances, and overruns the previously mentioned warm, sticky air, episodic showers and thunderstorms are expected. Although fine details are not yet apparent, this overall pattern often favors locally strong- severe thunderstorms and heavy downpours. As we draw closer to next week, we hope to add more clarity with respect to the timing and coverage of showers and storms.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

1025 mb surface high pressure over Western PA early this morning will drift slowly to the East-Southeast today, bringing VFR with light wind, excellent visibility and variable amounts of mainly thin cirrus clouds drifting SE from the Great Lakes region.

The only blemish in this otherwise excellent flying weather will be the likelihood of about 3-4 hours (08-12Z) of MVFR Vsbys in fog and perhaps a 1-2 hour period (08-10Z) of IFR throughout the deeper river valleys of Northern PA where the air/water temp difference will reach 25-28 deg F in some places.

HREF probs of IFR visibility are less than 20 percent at all TAF sites, but BFD, UNV, and IPT could still see brief periods of visibility less than 3 miles.

Winds will be light and variable during the daylight hours today and will once again diminish to near calm tonight/early Sunday.

Outlook...

Sun-Tue...Mainly VFR. Isold SHRA/TSRA possible.

Wed...Sct SHRA/TSRA with brief restrictions possible.

CTP WATCHES/WARNINGS/ADVISORIES

None.