870
FXUS61 KCTP 312335
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
735 PM EDT Mon Aug 31 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 multiday 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 multiday 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 /00Z TUESDAY THROUGH SATURDAY/...
Isolated showers and thunderstorms continue to plague the
airspace beginning at the 00Z TAF issuance. Evening convection
is expected to continue, but confidence in exact placement and
timing of these showers remains low. Coverage of convection was
initially expected to be greater at this time, and a lack of
storms would suggest weak forcing at the surface. A few mentions
additional overnight convection have been made, but near term
amendments may be needed for additional overnight storms.
Additionally, the initial probabilities for fog and low stratus
have come down as well. The most likely places to see fog
development tonight would be IPT/MDT/LNS, but confidence remains
low (30-40%) due to lack of prior rain near the surface. BFD
could see brief periods of MVFR low ceilings tonight, but IFR
seems unlikely.

Any fog or stratus that develops overnight will quickly mix out
in the early morning hours on Tuesday after sunrise. Attention
will then turn towards afternoon convection. Scattered showers
and thunderstorms are likely for the afternoon on Tuesday, but
there remains uncertainty as to the exact timing and placement.
Some guidance would suggest storms in the northwest as early as
15Z and others suggest convection may not arrive until 23Z.
Overall, expect periods of active convection across all
terminals in central PA on Tuesday bringing reductions to
visibilities and ceilings throughout the afternoon.

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...Bowen