textproduct: State College

WHAT HAS CHANGED

* Threat for elevated risk of wildfire spread has diminished since afternoon. * Nudged temperatures down tonight with high pressure overhead, calm winds, and dry air in place; widespread frost likely in northern/eastern PA.

KEY MESSAGES

1) Diminishing winds & cloud-free skies overnight, with frost north & east.

2) Warm up begins on Sunday and continues through the week; near-record warmth on tap for Wednesday and Thursday.

3) Unsettled weather expected next week, with several waves of showers and thunderstorms especially in the north and west.

DISCUSSION

KEY MESSAGE 1: Diminishing winds & cloud-free skies overnight, with frost north & east.

Overnight, high pressure moves across New York ushering in clear skies, calm winds, and efficient radiational cooling.

Have issued a Frost Advisory for temperatures falling below 36F in portions of the Mid and Lower Susquehanna Valley where the growing season is active and confidence is highest in frost formation.

Locations along and north of I-80 should be prepared for frost/freeze conditions tonight as well, despite the growing season not officially being active yet (and thus no Frost/Freeze products will be issued yet).

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KEY MESSAGE 2: Warm up begins on Sunday and continues through the upcoming week. Near-record warmth on tap for Wednesday and Thursday.

High pressure moves east and a warm/moist southwest flow will develop Sunday afternoon. That influx of warm/moist air will usher in a prolonged period of warmer-than-average temperatures through the upcoming week.

On the large-scale, our ensemble prediction systems are in good agreement that a mean upper-level trough will set up shop across the western CONUS, with downstream upper ridging taking hold from the Gulf states up the eastern seaboard. This will likely set the stage for a notable warming trend, with daily highs ranging from the 70s-mid 80s across central PA from Tuesday onward.

The latest forecast brings near-record temperatures across the region Wednesday morning through Friday morning, with lows Thursday morning forecast to be warmer than our average highs this time of year. Highs in the 70s and 80s will accompany lows in the 50s and 60s. Dewpoints will start to approach the 60F mark, so it will feel a bit humid but not overly uncomfortable.

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KEY MESSAGE 3: Unsettled weather expected next week, with several waves of showers and thunderstorms especially in the north and west.

The storm track for next week will be centered across the Great Lakes, with multiple waves of low pressure drifting into Ontario. A frontal boundary will set up generally west to east across New York and keep unsettled weather in place across northwest PA in particular. A few shortwaves along the prevailing trough could locally enhance the chance for severe weather, which is well supported by some of the NCAR Ensemble guidance that highlights an elevated severe threat Tuesday (NW), Wednesday (all of PA) and Thursday (southeast PA).

Shower and storm chances will be highest in northwest PA. Locations that have been wet lately will continue to see more rain, while drought-stricken locations across the southeast will see less rainfall.

AVIATION /01Z SUNDAY THROUGH THURSDAY/

VFR prevails across central PA as of 00Z, with high confidence (>90%) in VFR continuing through the end of the TAF period.

A high pressure moving across the Northeast will settle over the Western Atlantic, bringing southerly flow across the region on Sunday, along with mid/high clouds ahead of a low pressure that will be moving across the Northern Great Lakes. Some light rain showers may move across the Northern Tier (KBFD) as a warm front associated with this low pressure lifts across the area, with a PROB30 added for showers between 19Z-23Z based on the HREF. With that said, flight restrictions appear unlikely due to these showers, with VFR still expected to prevail.

Outlook...

Mon...Flight restrictions due to lowering ceilings and scattered showers, especially north and west.

Tue-Thu...VFR most of the time, but brief restrictions possible in hit and miss showers and thunderstorms, mainly across the north and west.

CTP WATCHES/WARNINGS/ADVISORIES

Frost Advisory from 2 AM to 8 AM EDT Sunday for PAZ027-028- 049>052-056-057-059-066.