Severe Thunderstorm Warning 320, NWS State College, PA

Area Forecast Discussion
National Weather Service State College PA
723 AM EDT Wed Sep 2 2026

.WHAT HAS CHANGED...
* A Heat Advisory has been issued for south central PA valid 11
  AM to 8 PM Thursday.

&&

.KEY MESSAGES...
1) Late summer surge of heat and humidity brings multi-day
severe thunderstorm and excessive rainfall threat to kickoff
September

&&

.DISCUSSION...
KEY MESSAGE 1: Late summer surge of heat and humidity brings
multi-day severe thunderstorm and excessive rainfall threat to
kickoff September

A series of mid level impulses tracking eastward along the
northern periphery of an expansive 500mb ridge will continue to
interact with anomalous moisture/instability and strong WNW flow
aloft to promote severe storm and excessive rain risk today and
tomorrow.

The first cluster of storms is already poised to move off of
Lake Erie into our NW zones between 7 and 8 AM. This cluster has
near continuous lightning and was severe warned along the lake
shore by the Cleveland WFO. Inland from the lake shore, the sfc
boundary layer is still rather stable this morning with near
150 J/kg of SBCIN, so this will at least somewhat offset the
severe wind potential across our NW zones. However the wind
threat could increase to the south and east IF the cluster is
maintained until mid-morning, by which time morning sunshine
will have eroded the sfc stable layer. Climatologically,
however, these morning MCSs rarely survive the nocturnal to
diurnal transition, and several CAMs do show it falling apart
before the boundary layer destabilizes.

The mesoscale severe weather setup will be complex this
afternoon into this evening, with key players being the presence
of a north-south stationary front / backdoor cold front across
the eastern zones, and whatever remains of the cold pool from
the morning MCS. These boundaries will likely be the focus for
new convection initiation this afternoon. Forecast vertical soundings
depict large, clockwise turning hodographs associated with a
strongly veered wind profile, with 0-3 km SRH on the order of
200-350 m2/s2 and 0-3km wind shear approaching 40 kts. Combined
with MLCAPE on the order of 1500-3000 J/kg, this setup will
likely yield both supercells and bowing line segments. If
supercells or southeast-bulging bow echos remain on the unstable
side of the stationary boundary and ingest this highly sheared
inflow, a couple stronger tornadoes and large hailers can not
be ruled out this afternoon into this evening. There will be a
large CAPE gradient across the stationary front, with limited
severe potential to its east.

Increased southwest to westerly flow on Thursday will push the
backdoor cold front out of the region, ushering in higher
temperatures and dewpoints. The Heat Index will make another run
at 100-104F across the southern zones, similar to what we saw on
Tuesday. We issued a Heat Advisory valid 11a-8p Thu for this
likely threat.

The severe risk will be focused more across the southern tier of
central PA by Thursday, and south of the PA-MD border on Friday.
An upper trough passage suggests additional showers and storms
on Friday, but fortunately the Labor Day weekend is trending
drier. The upper ridge is forecast to retrograde by the end of
the week which allows for a return to more seasonal temperatures.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
A brief period of highly localized heavy rain occurred INVOF
KUNV between 0430Z and 0530Z overnight as an outflow boundary
pushed wwd from earlier, widespread convection over the Middle
Susq Valley and points east. Two more, brief waves of SHRA/ and
potentially a few TSRA occurred through Altoona and now KJST as
the boundary pushed steadily Southwestward. Expect some areas of
LIFR/VLIFR until around 12-13Z tdy, esp in areas that had rain
yesterday and experienced some clearing/radiational cooling
resulting in fog formation.

The aforementioned frontal/outflow boundary and some mid and
upper level jet streak lift will combine to blossom areas of
strong to severe TSRA, the first in the form of a Mesoscale
Convective System (Moving SE at 30 kts acrs NW and Central PA
this morning), followed by a several hour lull, then more
convection/TSRA from the mid afternoon to mid evening hours
today.

PROB30/Tempo groups for -TSRA are highlighted in most terminals
(exception being KIPT at this time) given a signal on CAMs for
potential lines or clusters of showers/storms moving SEward
across the CWA as noted above.

Outlook...

Thu-Fri...Scattered SHRA/TSRA with brief restrictions possible;
morning fog possible.

Sat...SHRA/TSRA trending less likely as cold front moves
southward across the Commonwealth; morning fog possible.

Sun...VFR favored; morning fog possible.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 11 AM to 8 PM EDT Thursday for PAZ026>028-
035-036-056-057-059-063>066.

&&

WHAT HAS CHANGED...Colbert
KEY MESSAGES...Steinbugl/Colbert
DISCUSSION...Steinbugl/Colbert
AVIATION...Lambert/Bowen

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