textproduct: State College

WHAT HAS CHANGED

* Special Weather Statement for elevated risk of wildfire spread in effect for southern counties this 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) Abundant sunshine with diminishing winds & cloud-free skies today; frost tonight 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: Abundant sunshine with diminishing winds & cloud-free skies today; frost tonight north & east.

High pressure is building in quickly this afternoon as evidenced by a rapidly collapsing deck of stratocumulus this morning. Gusty northwest winds will continue to taper off this afternoon as heights rise and a boundary layer inversion strengthens.

Near or sub-30% RH values are possible across the Central and South-Central Mtns today thanks to downslope flow off the Alleghenies. A Special Weather Statement is in effect for counties across the south that didn't get much rain on Friday night.

Overnight, high pressure moves across New York ushering in continued 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 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 /18Z SATURDAY THROUGH THURSDAY/

VFR conditions prevail throughout the TAF period with clear skies today/tonight and increasing high clouds on Sunday. North- northwest winds will be sustained around 10 knots with gusts of 15 to 20 knots possible. Gusts may approach 25 knots at MDT and LNS. Winds will become lighter during the evening, decreasing to less than 5 knots after sunset.

Clouds will increase on Sunday as temperatures begin to increase from southwest to northeast. A few light showers are possible, especially across the northern tier.

Outlook...

Sun...VFR anticipated.

Mon-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.