textproduct: State College

WHAT HAS CHANGED

* Severe thunderstorm watch issued for much of the area for the evening (til 03Z).

KEY MESSAGES

0) Severe storm threat has increased through the evening

1) Dangerous heat persists today through Independence Day then eases next week

2) Risk managing severe thunderstorm and excessive rain outlooks Saturday through Monday

DISCUSSION

KEY MESSAGE 0: Severe storm threat has increased through the evening

Storms have flared up across the northern mountains along the lake breeze boundary. Tall cores with DCAPE values >1000J. Hail aloft may not reach the ground but the melting could further increase the downdraft strength. Damaging winds are the main threat. Near term model data solutions generally similar that convection will continue to the SE, but not very well on timing/SEwrd extent. Collab with neighboring offices and SPC has resulted in a appropriately generous areal coverage to the watch. The NW counties should be out of the woods shortly with post-storm stabilization, but the SE may not have things get through the cap until much later (past 00Z) - if they do. As usual, shear is better N and cap stronger S.

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KEY MESSAGE 1: Dangerous heat persists today through Independence Day then eases next week

The strong upper ridge responsible for this significant and dangerous heat wave today through the holiday weekend should flatten as we head into next week. This pattern transition will allow temperatures to return to values more typical of early July.

Extreme heat headlines remain in effect today and Saturday, with the only change being the addition of Fulton County to the heat advisory on July 4th.

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KEY MESSAGE 2: Risk managing severe thunderstorm and excessive rain outlooks Saturday through Monday

The overall potential convective evolution over the next 3 days remains uncertain/unclear. Proximity to the heat dome core casts some doubt for today with warm mid levels and marginal deep layer shear profiles (0-3 KM Bulk shear ranging from 20-25 kts across south PA to around 30 kts over the north), although most CAMS (including HREF and REFS) seem to agree that widely scattered storms could develop near the Lake Erie Breeze boundary near and just SE of the I-90 corridor and track east southeastward later this evening.

A small-scale mid/upper level low seen in water vapor imagery is drifting slowly north from the KY/OH border late this AM and will enhance diffluent flow/diff PVA aloft across Eastern Ohio and Western PA to create a more favorable environment for the convection to break the warm mid level cap and grow into pulse or multicell clusters of strong to svr tsra.

We'll also be watching the SWD progression of an outflow boundary shooting out from TSRA moving across the Niagara Frontier of Western NY/SE Ont, and an ill defined MVC that will be heading across the Southern tip of Lake Huron shortly and along the North shore of Lake Erie by early this afternoon.

Otherwise, rather low confidence and predictability forecast in severe wx terms extends through the holiday weekend, with the strongest precip signal in the Sunday through Monday timeframe. WPC now has a pair of level 2/4 excessive rain outlooks covering much of CPA in what appears to be a favorable heavy rain setup complete with hi pwats pooling along a wavy, east to west oriented frontal zone.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

Next wave of isolated tstms moving in from the west early this eve so have added PROB30s for JST, AOO, UNV to highlight the thunderstorm potential with brief reductions.

Otherwise, widespread VFR conditions are expected through 18z Sat with mainly dry conditions. But after that, scattered to numerous thunderstorms are expected to develop, with occasional impacts possible at terminals areawide, starting early afternoon at BFD, mid afternoon at JST/AOO/UNV/IPT and late afternoon at MDT/LNS. Western areas of CWA, mainly west of Susq River, should see convective activity diminish by early evening.

Density altitude concerns will continue into tomorrow across Central PA.

Outlook...

Sat...Patchy AM fog; otherwise VFR. Hot & humid with PM t-storms psbl. High density altitude concerns possible.

Sun-Tue...Restrictions possible in afternoon t-storms.

CLIMATE

Bradford reached 90 degrees yesterday afternoon 7/2. This tied the old record of 90 degrees set back in 1966.

Williamsport reached 100 degrees, breaking the old record of 99 degrees set back in 1911 and 1931.

Harrisburg did reach 102 degrees, just short of the record of 104 degrees set back in 1966.

Many record highs were set in 1966 around this time of year, while record lows were common back in 1982.

Earlier information below.

Bradford reached 89 degrees Wed, breaking the old record of 88 degrees set in 1963. Harrisburg came up one degree short of tying their own record max Wed.

Triple digit max temps are forecast in the Lower Susq Valley (LSV) today and Friday, and 90s for Saturday.

The last time Harrisburg observed consecutive days with maxT greater than or equal to 100F was back in 2011 on July 21-22.

The record number of consecutive days with maxT >= 100F is 3 and has occurred 5 times: (all in the month of July)

1999-07-16 to 1999-07-18 1999-07-04 to 1999-07-06 1991-07-19 to 1991-07-21 1966-07-02 to 1966-07-04 1936-07-09 to 1936-07-11

The last time Harrisburg hit the century mark was July 16th in 2024. Prior to that, it was July 19th in 2020.

Harrisburg averages 1 day annually with a maxT >100F. The most number of days observed in a year is 6 in 1999.

The record maxes for the next few days are in jeopardy:

Station/Date...07/02...07/03...07/04...07/05. MDT.............104.....107.....104.....102.. IPT..............99.....100.....100.....100.. AOO..............97......97......97......94.. JST..............98.....100.....100.....101.. BFD..............90......91......91......91..

CTP WATCHES/WARNINGS/ADVISORIES

Heat Advisory until 8 PM EDT Saturday for PAZ019-026>028-035- 036-045-046-049>053-056-058-063. Extreme Heat Warning until 8 PM EDT Saturday for PAZ057-059- 064>066.