textproduct: State College

WHAT HAS CHANGED

* Little, if any, changes. Waiting on new guidance to determine if Flash Flood Watch is needed.

KEY MESSAGES

1) Beautiful weather to close out the week, but an increasing chance for widespread moderate to perhaps heavy rain late Saturday into early Sunday.

DISCUSSION

KEY MESSAGE 1: Beautiful weather to close out the week, but an increasing chance for widespread moderate to perhaps heavy rain late Saturday into early Sunday.

Little to change this evening and overnight. However, we're still evaluating whether to post a flood watch. Recent hi-res guidance does put numerous heavy rainers over the area. But, the problem is: where? Some of the very newest guidance would make the axis of heaviest precip/thunderstorms about 50-60 miles N of where the 12Z guidance had some occurring. With uncertainty high as it is and FFG getting higher slowly, too, we'll punt to the mid shift.

Prev...

Surface high pressure centered over the Catskill region this evening will move off the Southern New England Coast tonight. A southeasterly to southerly flow will develop late tonight into Saturday and low level moisture lurking just south of the Mason/Dixon line will push steadily NE across the state on Saturday.

A notable axis of streamline convergence shifting gradually east across Central PA late Sat afternoon/Sat night will provide increasing llvl theta-E advection and numerous showers with several tenths of an inch of rainfall likely across at least the SE half to two thirds of the CWA by early Sunday.

A few PM TSRA are possible Saturday and/or Sunday afternoons, especially over the western mtns where MU CAPE will climb above 1000 j/kg with pocket of 0-1 KM EHI in the 1-1.5 m2/s2 range.

The timing of the thickening cloud cover late tonight/early Sat morning will allow for moderate radiational cooling of the ground tonight with the llvl inversion being difficult to break for the first half of Saturday across our Central and NE zones. So, Max Temps should turn out to be a few to several deg F lower than today's

A more-active (wetter) pattern is in store for Mon- Tues. But, the flat upper ridge over the southern half of the CONUS will make it difficult for deep moisture to make it into PA ahead of any shots of atmos forcing. The week could end dry as the upper ridge pumps up over the central CONUS.

AVIATION /02Z SATURDAY THROUGH WEDNESDAY/

Tonight will start off clear, with cloud cover overspreading the area from SW to NE late tonight/early Saturday as a disturbance approaches from the Tennessee Valley. The western terminals of JST and AOO could see some low ceilings tonight with the highest confidence in MVFR conditions occurring after 08Z. There is some guidance that would suggest a brief period of IFR ceilings at these two sites, but confidence is too low for that to be the prevailing condition. Fog appears unlikely tonight with clouds moving in, so the main concerns will just be the low clouds in the west. Elsewhere should remain VFR through the night.

It will be dry through Saturday morning before convection is likely to develop over the Alleghenies in the early afternoon ahead of the main front. The presence of lightning is uncertain at this time due to the limited instability that will be available at this time. The main front will bring more widespread rain across the region Saturday night from northwest to southeast, and will likely begin to impact sites starting in the northwest at BFD near 00Z Sunday.

Outlook...

Sat - Mainly VFR early, then MVFR and rain developing Saturday night.

Sun...Early MVFR/IFR and moderate rainshowers across the state. Additional SHRA/TSRA in the afternoon.

Mon...Primarily VFR conditions, with some potential for afternoon SHRA/TSRA.

Tue...Mainly VFR with a few showers possible over NW PA.

CTP WATCHES/WARNINGS/ADVISORIES

None.