textproduct: State College

WHAT HAS CHANGED

* Added +FG AOA 2000ft across the western/northern Alleghenies * Added areas of frost Thursday-Saturday night

KEY MESSAGES

1) Wet Wednesday with widespread drenching rainfall and a few strong thunderstorms possible in southwest PA

2) Chilly pattern for the end of April with frost/freeze risk through the first weekend of May

DISCUSSION

KEY MESSAGE 1: Wet Wednesday with widespread drenching rainfall and a few strong thunderstorms possible in southwest PA

Extensive low clouds and ridge-shrouding/locally dense fog across CPA this morning. We added +FG at elevations AOA 2000ft based on blend of ASOS/RWIS data with visibility 0.5-1kft.

Drenching rainfall is expected to expand from southwest to northeast through the afternoon and evening before tapering off and shifting to the east late tonight into early Thursday morning. Rain may be heavy at times particularly across the NW Alleghenies with >1" amounts possible based on HREF/REFS PMM QPF signal. While largely beneficial especially in D1-D2 drought areas in the far southeast part of the CWA, some roadway ponding or minor low lying/poor drainage runoff issues are possible.

SPC has maintained a level 1/5 MRGL risk SWO over southwest PA, but the lack of instability continues to cast considerable uncertainty in the development of strong storms. Secondary low formation along/south of the MD line suggests greatest severe storm risk is probably farther to the south into the warm sector over WV/VA. --------------------------------------------------------------

KEY MESSAGE 2: Chilly pattern for the end of April with frost/freeze risk through the first weekend of May

Several disturbances rotating around a persistent upper level closed low centered over Ontario and Quebec will help to reinforce broadly deep troughing across the eastern U.S. into next week. This pattern will keep conditions cool and unsettled with temperatures below seasonal norms. Chilly nighttime lows will also lead to frost and freeze concerns Thursday-Saturday night. The growing season is now active across all CPA zones.

AVIATION /08Z WEDNESDAY THROUGH SUNDAY/

An area of low pressure will move northeast over the Ohio River Valley and cross Central PA late this afternoon through early tonight.

Gradually lowering Cigs and Vsbys will precede and accompany a broad area of rain near and to the north of the low's track.

Look for LIFR conditions at KBFD through the mid-late morning hours at KBFD likely improving slightly to plain IFR CIGS and VSBYS for the afternoon and early evening today. In the moist upslope flow in the wake of the rainfall tonight, cigs will likely drop several hundred feet - back into the LIFR range while vsbys fall into the IFR category.

KJST has seen the best CIGS and overall conditions (VFR) so far as they're residing in a narrow warm sector with a light SSW breeze.

Elsewhere, slightly cooler air and a light east-southeast wind was leading to widespread MVFR Cigs, but mainly VFR vsbys.

Removed low vsbys as the cloud cover should help to maintain a few to several deg F temp/dewpoints spread with MVFR vsbys through at least this morning, prior to the onset of the steadier rain arriving from the SW later this morning and early this afternoon. The brunt of the steadier rain will fall in a 6 to 8 hour window at most airfields.

After the aforementioned sfc low heads to the NJ/Southern New England coast tonight, the leftover llvl moisture and light NW/upslope breeze will cause lowering Cigs and Vsbys into the LIFR range across the Western Mtns of PA and MVFR to IFR elsewhere.

Outlook...

Wed...MVFR/IFR favored due to low cloud ceilings & rain overspreading the region. A few -TSRA are possible across Southern PA this afternoon, but they weren't included in any TAFS as a result of the fairly low probability and generally weak instability to support their development.

Thu...VFR/MVFR in the morning as rain ends west to east, becoming VFR in the afternoon.

Fri-Sat...Mainly VFR with brief restrictions possible in showers.

Sun...Restrictions possible northwest in -RA and possibly some -SN.

CTP WATCHES/WARNINGS/ADVISORIES

None.