textproduct: State College

WHAT HAS CHANGED

* Increased clouds through the morning across the Northwest Mountains and introduced a 20-30 POP for snow showers there as a spoke of a cold pool aloft moves into NW PA.

KEY MESSAGES

1) Cool and unsettled pattern continues this weekend with a frost/freeze risk early today across Central and Northern PA and again tonight and early Sunday across a larger area in Central and Southern PA.

DISCUSSION

KEY MESSAGE 1: Cool and unsettled pattern continues this weekend with a frost/freeze risk early today across Central and Northern PA and again tonight and early Sunday across a larger area in Central and Southern PA.

Several spokes of energy rotating around a broad, slow-moving upper level closed low centered over Ontario and Quebec will lead to variable amounts of clouds and a low probability for rain and snow showers, primarily across the NW Mtns of PA today.

Introduced the 20-30 POP for -SHSN across the NW Mtns this morning as RAP Guidance shows 0.5 KM Wet bulb temps of -3 to -5C there at 08Z Sat.

This pattern will bring variable amounts of clouds and scattered late morning/afternoon sprinkles over roughly the NW half of the state.

Freeze Warnings and Frost Advisories that are currently in effect through 13Z today across Central and NW Pa will almost certainly be issued again for tonight/early Sunday and expanded to the SE into the Lower Susq Valley and Western Poconos as we expect to see the lowest temperatures of this current cool spell.

There is still some uncertainty regarding the southeastward extent of frost as there will be a rather tight pressure gradient across the region due to a developing area of low pressure off of the coast.

Temperatures will be trending warmer for the beginning of the week, but all guidance indicates that unsettled weather will continue with multiple chances for rain next week, with the highest PoPs Wed- Thu. Latest guidance also suggests a potential return of frost/freeze conditions by Thursday and Friday nights.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

VFR conditions prevail across much of central Pennsylvania this morning with some MVFR ceilings across far southeastern Pennsylvania (LNS) as of 10Z observations. All model guidance points towards improvement towards VFR conditions by 12Z Saturday with widespread VFR flight conditions expected throughout much of the 12Z TAF package. Main concern for restrictions will come with respect to scattered rain shower coverage across portions of central Pennsylvania, mainly in the 18Z Saturday to 00Z Sunday timeframe. Recent hi-res guidance continues to point best chances towards BFD/JST/IPT/UNV today; however, have limited mentions to only JST where HREF outlines slightly higher probabilities for precipitation. These chances still barely eclipse ~30%, thus utilizing a PROB30 group is the best opening offer for the 12Z TAF package, but still would caution quick ceiling drop potential in shower mentions in the near-term at BFD, along with UNV/IPT in the 18Z-22Z window. Some signals exist for clearing after sunset based on GLAMP guidance, thus have started to hint towards widespread VFR (potentially with SKC) conditions towards the end of the TAF package at all airfields outside of BFD where lingering low- level moisture promotes low-level cloud deck mentions.

Outlook...

Sun...SHRA moves in late; otherwise, VFR expected.

Mon...SHRA potential increases during PM hours, some TSRA possible across N/W PA. Restrictions possible.

Tue...SHRA becomes more widespread, TSRA chances expand across much of central PA. Restrictions possible.

Wed...Scattered SHRA remain. Restrictions possible.

CTP WATCHES/WARNINGS/ADVISORIES

Freeze Warning until 9 AM EDT this morning for PAZ004>006- 010>012-017-018-024-033-037. Frost Advisory until 9 AM EDT this morning for PAZ019-025>028- 034>036-041-042-045-046-049-050-056.