694
FXUS61 KCTP 040008
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
808 PM EDT Wed Sep 3 2025

.SYNOPSIS...
* Sunny and dry today as high pressure remains in control.
* A series of cold fronts will bring a risk for strong
  thunderstorms Thursday and Saturday.
* Temperatures trend below normal again next week with high
  pressure and dry weather prevailing.

&&

.NEAR TERM /THROUGH THURSDAY/...
Another gorgeous day on tap with high pressure bringing dry
conditions and plenty of sunshine. Fair weather cumulus will
develop again by early afternoon as high temperatures get into
the middle 70s to low 80s. Light southerly winds  A light
shower or two cannot be ruled out in the Laurel Highlands later
this evening as moisture ahead of an approaching cold front
begins to advect north.

Southerly winds will back to southeasterly or easterly overnight
to the east of the Susquehanna Valley. This will support low
clouds and/or fog along and east of US-15. Farther west, high
clouds will begin to move overhead by daybreak ahead of the next
weather maker. A few showers are possible northwest of I-99/I-80
corridor overnight as well, though intensity/rainfall
accumulation should be insignificant. Lows on Thursday morning
will range from near 50 in the typical cool spots in the
northwest mountains to near 60 in the Lower Susquehanna Valley.

&&

.SHORT TERM /THURSDAY NIGHT/...
Under a prevailing upper trough, a mid-level vorticity maximum
will rotate through the Mid Atlantic on Thursday accompanied by
a surface cold front. Convection associated with the cold front
should be fairly weak by daybreak Thursday as it moves across
Lake Erie and into northwest PA. As the front moves east,
these showers and storm should reintensify as they encounter sufficient
moisture with dewpoints in the upper 50s to low 60s, marginal
instability (up to 750 J/kg), and ample shear (30 - 40kts).

Convection allowing models depict potential for two distinct
rounds of showers/storms. The first would be associated with the
aforementioned line of storms that will advance into southeast
PA by later afternoon and evening. The second would be along
the surface cold front, which likely struggles to get past the
I-99/I-80 corridor by Thursday evening. The SPC has issued a
Marginal Risk for nearly all of Pennsylvania. The best shear
will be across northern PA into New York, while the best
instability will be well south of the region (Southern
Appalachians). Pennsylvania will have sufficient amounts of
instability and shear to support a marginal threat of damaging
winds.

Highs on Thursday will range from the mid 60s in northwest PA
where more clouds/precipitation will keep temperatures at bay,
to the mid 80s in southeast PA where most of the day should
remain sunny or at least partly cloudy before convection
arrives. On Thursday night, lower dewpoints will filter into
northwest PA behind the cold front allowing temperatures to drop
into the mid 40s. Farther southeast, more clouds/lingering
showers will keep temperatures much more mild in the upper 50s
to lower 60s.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
For the long term period, a prevailing upper trough across the
eastern US will remain in place, perhaps lifting a bit by the
middle of next week. On Friday, high pressure will briefly
regain control of the region giving way to mostly sunny skies,
dry conditions, and another seasonably mild day. Noting that
Thursday`s cold front will get hung up across the Central
Mountains, it will still be rather humid on Friday afternoon in
southeast PA.

By Saturday, a stronger cold front (compared to Thursday) will
sweep through the Commonwealth and bring a renewed chance for
showers and thunderstorms. There remains some uncertainty
regarding how much instability will be in place ahead of the
front, but scattered strong to severe thunderstorms seem like a
good bet. As is typical with these systems, the best chance for
severe will likely be in southeast PA and an SPC Marginal Risk
is probable for Saturday.

After the cold front sweeps through, another fall-like pattern
will settle in for the second half of the weekend and into next
week. The airmass moving overhead will be the coolest of the
season so far. Highs in the 60s and 70s will pair with lows in
the 30s to 50s. Frost or freeze conditions seem like a good bet
for the typical cool spots in northwest PA early next week along
with river valley fog. Abundant sunshine and dry conditions are
favored, with increasing moisture and chances for rain toward
the middle to end of the week.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
Mostly clear skies are expected in the near-term (through
03Z-06Z Thursday) with increasing high-level clouds overnight as
a cold front approaches central Pennsylvania. Recent HREF/RAP
model guidance do indicate a slightly slower progression in
cloud cover overspreading the area, tracking relatively close to
current satellite observations. Given observational trends have
pulled back on the previous forecast slightly with high-level
clouds generally (~70-80% confidence) +1/+2 hours ahead of
precipitation mentions closer to 12Z across the western
terminals. While clear skies are expected, low-levels are
expected to remain dry enough to lower any expectations for fog
across central Pennsylvania overnight.

Slightly higher confidence (~50-60%) with respect to onset
timing of showers for the 00Z TAF package as HREF/RAP/GLAMP show
modest agreement; however, there remains *just* enough
uncertainty to warrant a PROB30 on the front end as the cold
front approaches all terminals outside of MDT/LNS between
13Z-17Z. Model guidance does start to deviate slightly across
the Lower Susquehanna Valley; however, and have blended recent
HREF/GLAMP guidance to gather a plausible onset timing for
precipitation after 18Z with moderate (~40-50%) confidence.

There remain one key point about the 00Z TAF cycle that will
need to be monitored in future issuances. While no thunderstorm
mentions are included in the 00Z TAF cycle, there is an
increasing chance for thunderstorms after 18Z Thursday,
generally east of a KELM/KUNV/KCBE line. No mentions are
included in the 00Z TAF cycle as there still remains quite a bit
of uncertainty on where/when thunderstorm chances will develop
on Thursday; however, best timing at UNV remains in the 18Z-21Z
timeframe, IPT in the 20-23Z timeframe, and MDT/LNS generally
after 22Z. Thunderstorms Thursday afternoon/evening will bring
about some potential for gusty winds that could bring hazardous
conditions to the terminals/air space of central Pennsylvania.

Outlook...

Fri...Showers lingering, mainly E PA.

Sat...Chance of SHRA w/ TSRA possible.

Sun-Mon...Clearing with VFR conditions. Breezy on Sunday.

&&

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

&&

$$

SYNOPSIS...Banghoff
NEAR TERM...Banghoff
SHORT TERM...Banghoff
LONG TERM...Banghoff
AVIATION...NPB