Severe Thunderstorm Warning 184, NWS State College, PA

Area Forecast Discussion
National Weather Service State College PA
1048 AM EDT Fri Jul 25 2025

.SYNOPSIS...
* Max Heat Index reaches/exceeds 100F this afternoon for areas
  near and south of Interstate 80
* Rounds of thunderstorms are probable this weekend with
  continued hot/humid weather before a cooldown arrives to kick
  off the month of August

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
1045 am update... We've added a row of counties (from Columbia
west-southwest down to Huntingdon) to the Heat Advisory this
afternoon.

Meso-analysis and sounding interrogation late this morning shows
a warm and relatively moist layer of air just above the surface
across the southern half of PA, which should somewhat inhibit
the ability to mix surface dew points downward this afternoon.
Slightly higher dew points (up to the mid 70s) edges Heat Index
values above 100F a bit farther to the north.

Previous discussion... Showers and TSRA moving east into the
western forecast area border along and just ahead of a cold
front. Area is diminishing as it moves east and left slight to
low chance PoPs with ridging aloft/heat dome.

HeatRisk ramps to level 3 of 4 (major) across most of CPA
Friday with max heat index values 95-100+ degrees fcst across
the central and eastern valleys particularly near and southeast
of the I99/US220 corridor. We issued a heat advisory for a
portion of south central PA where confidence is highest (>80%)
in observing max heat indices 100-104F. There may be a few
isolated 105F or slightly higher but not enough to warrant any
ramping of the heat products. Heat Advisory will last from
afternoon through sunset.

Latest HREF data suggests iso-sct t-storms are likely to
develop along the eastern I-99 / I-80 corridor during the mid
afternoon and slide southeast through sunset. SPC keeps a
marginal risk (1 of 5) across this area with any higher risk
just to the east of our forecast area today.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
Similar to the longer term pattern this summer, model data
indicates the front stalls out and becomes wavy or quasi
stationary over central PA by 12Z Sat. Any locations that
receive rain Friday may also experience some low clouds/fog on
Saturday morning as moisture rich air and weak forcing remains
in place. Best chance at this time is in the northwest
mountains. On Saturday, a low amplitude shortwave trough
translating around the northern periphery of the upper ridge
should trigger one or more rounds of showers and storms along
wavy/stationary/warm front into Saturday night. Latest guidance
has trended down quite a bit in terms of storm coverage, with
some indications that much of the day on Saturday could be rain
free for most of the region (best chance for widespread/longer-
lasting showers/storms in the Laurels).

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Best large scale forcing will now arrive on Sunday with the
passage of the low amplitude mid level trough. This should
ignite another round of showers and storms with max QPF signal
over eastern PA. We should get a little break in precip Sunday
night into Monday before the next quick moving wave in the WNW
flow arrives Monday night into Tuesday. Timing of waves and
associated precip is likely to change to some extent for early
next week based on the current spread/diffs in the model data.
Hot/humid conditions will stick around through the extended
period as well, with heat index values flirting with the century
mark a couple days.

Ensemble data suggests a pattern change is likely to evolve by
the end of the forecast period/beginning of August as the upper
level flow becomes more amplified, with the ridge building
north across the Rockies and a trough from Canada building
southward across the Great Lakes and the Northeast. This should
bring a return to much more pleasant conditions behind a cold
front on Thursday.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
Few showers and storms to the west at sunrise.

With winds becoming westerly early on, expect showers
and storms to be rather scattered in nature today, then
as in past events, as convergence will be more limited.

More in the way in dry weather by next Monday.

Outlook...

Sat-Sun...Mainly dry, not as hot, with isolated to scattered
TSRA and brief restrictions possible each afternoon/evening.

Mon-Tue...VFR.

&&

.CLIMATE...
A record high temperature of 87 degrees was tied at Bradford
Thursday. This ties the record set back in 2001.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM EDT this evening for PAZ026>028-035-
036-049>053-056>059-063>066.

&&

SYNOPSIS...Dangelo
NEAR TERM...Jurewicz/Dangelo/Tyburski
SHORT TERM...Tyburski
LONG TERM...Steinbugl/Banghoff/Tyburski
AVIATION...Martin
CLIMATE...NPB

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