textproduct: State College

WHAT HAS CHANGED

* Severe Thunderstorm Watch 686 issued for most of central PA until 8PM this evening * Freeze Watch issued for most of central PA late Saturday night into early Sunday morning

KEY MESSAGES

1) Scattered damaging winds possible this afternoon and evening

2) Blustery and much turning much colder tonight and Saturday

3) Frost and freeze conditions Saturday night into early Sunday

DISCUSSION

KEY MESSAGE 1: Scattered damaging winds possible this afternoon and evening

Convection has gradually increased in intensity crossing the south central Alleghenies early this afternoon along/just ahead of a surface cold front. Downstream, stronger heating has been ongoing where low stratus have eroded from earlier this morning. Temperatures have warmed into the 70s where this stronger heating has occurred, and weak destabilization is supporting expanding coverage of storms. While instability and lapse rates are expected to remain rather mild resulting in a low-topped , strong deep- layer flow will support transient organized bowing structures, and strong gusts at the surface largely in the absence of significant lightning. The main damaging wind threat appears focus along and to the southeast of KJST/KUNV/KIPT. A few line- embedded mesocirculations could also occur, which could yield a brief tornado.

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KEY MESSAGE 2: Blustery and much turning much colder tonight and Saturday

The post-frontal winds gusting 25-35 mph direct much colder air into CPA through tonight into Saturday. Clouds and winds have resulted in slightly warmer overnight low temps so advective freeze is probably off the table for the NW mtns. Low level flow turns more northerly overnight which should limit lake effect response, although a few rain/snow showers remain possible over the higher terrain. Min wind chills by Saturday morning will be in the 25-35F range across the western and central Alleghenies. Highs on Saturday will be 20 to 30 degrees colder vs. Friday.

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KEY MESSAGE 3: Frost and freeze conditions Saturday night into early Sunday

Frost/freeze still looks good for Saturday night into early Sunday morning as clouds fade and winds subside. Issued Freeze watch for active zones in the late innings of the growing season.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

Brief IFR restrictions expected along cold front and associated line of gusty showers/storms moving southeast from KJST/KUNV/KIPT. Wind shift from 230-270 to 300-360 degrees behind the front will result in MVFR cigs with IFR most likely at KBFD/KJST. Expect frequent gusts 25-30kts into Saturday before gradually subsiding by 00Z Sunday. Return to widespread VFR expected by Saturday night.

Outlook...

Sun-Tue...AM fog possible; otherwise, VFR conditions prevail.

CTP WATCHES/WARNINGS/ADVISORIES

Freeze Watch from late Saturday night through Sunday morning for PAZ004-006-010>012-017>019-024>028-033>037-041-042-045-046- 049>053-056>059-063>066.