textproduct: State College

WHAT HAS CHANGED

No significant changes with this update.

KEY MESSAGES

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 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 /14Z FRIDAY THROUGH TUESDAY/

VFR conditions are expected through the TAF period with mainly dry conditions likely through the rest of this morning. Scattered showers and thunderstorms are expected to develop along and north of I-80 this afternoon (probably first just SE of Lake Erie and the I-90 corridor), but there is still quite a bit of uncertainty regarding the exact timing and coverage of storms. For now, we have added PROB30s for BFD, UNV, and IPT to highlight the thunderstorm potential, but this will need to be refined throughout the day as confidence increases. It is possible that storms could develop farther to the south as well, but there is less than a 30 percent chance that they impact any of the other TAF sites. Some of the storms that develop will be capable of producing strong wind gusts, potentially in excess of 40 knots. Heavy rainfall may also briefly reduce visibility if storms move directly over any airfields.

Very hot conditions are expected once again today, with highs expected to be in the 90s/low 100s. This will continue to lead to density altitude concerns 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 this evening for PAZ004>006- 010>012-017-018-024-033-037-041-042. Extreme Heat Warning until 8 PM EDT this evening for PAZ019- 025>028-034>036-045-046-049>053-056-058-063. Heat Advisory from 8 PM this evening to 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.