textproduct: State College

WHAT HAS CHANGED

* The Frost Advisory for tonight has been expanded to include Clearfield and Tioga Counties.

KEY MESSAGES

1) Periods of showers possible through Friday, then rain likely Saturday and part of Sunday.

2) Chillier to end the week with frost/freeze potential returning tonight and tomorrow night.

DISCUSSION

KEY MESSAGE 1: Periods of showers possible through Friday, then rain likely Saturday and part of Sunday.

The bulk of the rain from earlier today has moved off to the east, though patchy drizzle and a few showers will remain possible through the rest of the day. A wave of low pressure is expected to ride along a cold front as it exits the region to the east later this evening, and this may bring a few showers back into southeastern PA. Any additional rainfall will be light. Most of Central Pennsylvania is expected to be dry tomorrow and Friday, but shortwave troughs rotating through the base of a longwave trough may trigger a few showers both days. Rain chances increase for the weekend as multiple disturbances track across the area.

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KEY MESSAGE 2: Chillier to end the week with frost/freeze potential returning tonight and tomorrow night.

High pressure building in behind the cold front tonight will allow for skies to at least partially clear out over northwest PA and for winds to become light. This should support efficient radiational cooling and we expect temperatures to fall into the mid 30s over much of the northern tier. Frost formation appears most likely over the northwestern corner of the CWA and we have issued a Frost Advisory for Warren, McKean, Elk, Cameron, Clearfield, Potter, and Tioga Counties which is in effect from midnight through 8 am Friday. Patchy frost may still be possible outside of the advisory if skies clear out at least a few hours before sunrise.

Another chilly night is expected for Thursday night with frost and freeze conditions possible once again. Not many pixels of 32F or lower on the MinT grid, but a small (20%) risk is there for someone to have a freeze across the NW. The risk for frost is much more - around 70% for the Allegheny Plateau and Laurel Highlands.

AVIATION /06Z THURSDAY THROUGH MONDAY/

Back edge of the lower-level cloud deck roughly stationed along a YNG-HLG-UNI line will continue tracking further east this morning, with widespread SKC expected on the end of the back-end of this cloud deck. A brief period of SCT-BKN is possible just ahead of SKC; however, VFR conditions are virtually certain overnight through 12Z Thursday. Some scattered rain showers across SE PA (MDT/LNS) will bring some chances; however, this will be on a subtle downtrend between 06-09Z Thursday. Highest potential for SHRA at the airfields will be limited to LNS, thus have outlined a slightly lower-level (still VFR) cloud deck.

Model guidance does indicate some scattered SHRA, mainly impacting N/W PA throughout the late afternoon and early evening hours, generally between 17Z Thur and 04Z Fri. Recent HREF/GLAMP model guidance is not super robust with respect to mentions; however, could see mentions being added in at BFD/IPT/UNV in future TAF packages but given the lower (< 30%) confidence have removed any mentions at this time. All model guidance points towards another (mostly) clear overnight period, so have started to outline some clearing in the 00Z-06Z Thur timeframe this cycle, highest confidence across E PA (MDT/LNS/IPT/UNV).

Outlook...

Fri...VFR with some spotty afternoon/evening SHRA.

Sat...Restrictions possible in RA.

Sun...VFR favored early, with restrictions becoming more likely in the afternoon as cold front moves SE. SHRA with isolated TSRA possible as cold front passes through.

Mon...VFR favored, with restrictions possible SE from lingering SHRA/RA.

CTP WATCHES/WARNINGS/ADVISORIES

Frost Advisory until 8 AM EDT this morning for PAZ004>006-010- 011-017-037.