631
FXUS61 KCTP 010625
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
225 AM EDT Tue Sep 1 2026

.WHAT HAS CHANGED...
* Adjusted POP/Wx to better align with Day 2-4 SPC SLGT risk

&&

.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:

A series of mid level impulses tracking eastward along the
northern periphery of an expansive 500mb ridge will interact
with anomalous moisture/instability and strong WNW flow aloft
to promote a multi-day severe storm and excessive rain risk
across portions of CPA Tuesday-Thursday. A surge of late summer
heat (max temps 80-90F range) with dewpoints in upper 60s to low
70s will result in a very moist boundary layer with impressive
MLCAPE values in the neighborhood of 2-3k J/kg given mid level
lapse rates around 7 C/km. Forecast soundings also show robust
deep layer/effective shear values and appreciably curved,
sizable low level hodographs. As such, a couple of supercells
will be possible. Severe wind and hail are the main threats,
though a tornado or two may also occur. On balance, the
environmental parameters are quite bullish for severe storm
potential. However, timing (time of day), speed, and location
of each mid level impulse will be key factors that could
modulate the bullish severe setup to some extent. Increasing
MUCAPE values late tonight through Tuesday morning suggest
storms/severe risk likely won`t be tied to the typical diurnal
cycle. The severe risk will shift to the south of CPA by
Friday, but an upper trough passage suggests some lingering
shower activity into the weekend.

The late summer heat is forecast to peak Tuesday and Wednesday
with very warm nights +10-20F above the historical average and
max heat indices approaching advisory levels/century mark
across parts of south central PA. The upper ridge is forecast to
retrograde by the end of the week which allows for increased
troughing and a return to more seasonal temperatures for early
September.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
Warm frontal boundary extending from the Eastern Finger Lakes
region, south through the Western Poconos and SE PA will meander
a bit to the south and west over the next 24 to 48 hours. This
airmass boundary will provide an avenue to a few rounds of
showers and afternoon/evening thunderstorms to track southeast
along.

The most likely places to see fog/low CIGS through the mid
morning hours today will be at IPT and to a lesser degree at
MDT/LNS.

BFD could see brief periods of MVFR ceilings early today, but
IFR seems unlikely.

Any fog or stratus will quickly mix out in the 12-13Z period.
Attention will then turn towards afternoon convection.

Isolated to scattered showers and thunderstorms are expected
for the mid afternoon to early evening hour today, but there
remains uncertainty as to the exact timing and placement given
the lack of any larger-scale, deep-layer forcing and the
presence of the subsiding, thermally indirect branch (right exit
region) of a 40-50 kt mid/upper level jet max embedded in the
NW flow.

Some guidance would suggest storms in the northwest as early as
15Z and others suggest convection may not arrive until 23Z.
Overall, expect the potential for brief periods of active
convection at all terminals across central PA this
afternoon/evening, with a hedge toward the airfields across the
eastern third of PA. Brief reductions to visibilities and
ceilings to low end MVFR or IFR are possible in the 18Z Tue-02Z
Wed period.

Outlook...

Tue-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.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

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