855
FXUS61 KCTP 070850
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
450 AM EDT Tue Oct 7 2025

.SYNOPSIS...
* Beneficial rainfall today as a cold front approaches
* Breezy and chilly Wednesday with decreasing clouds & lower
  humidity
* Frost/freeze likely Thursday and Friday morning with fall-like
  weather finally hanging around for awhile

&&

.NEAR TERM /THROUGH TONIGHT/...
Clouds will continue to increase/thicken up from the southwest this
morning as the nose of a southern southwesterly LLJ segment
helps to advect a plume of tropical moisture (with Central GoAM
origin) NE up the Ohio River Valley. Could see some fog/low
clouds develop east of the Susquehanna River by daybreak
(already seeing some low clouds east of Lancaster County toward
Philadelphia).

Latest radar imagery showers showers just getting to western PA,
and hi res guidance depicts some spotty light showers drifting
across NW half of the CWA with more numerous showers or even
steady light rain entering the NW and WCentral Mtns of the state
around 11-12Z this morning. Temperatures at daybreak will
generally be in the mid to upper 50s.

Today will be another warm one southeast of the I-99/I-80
corridor with temperatures getting to near 80 degrees again.
Farther west and north of there, clouds/rain will keep
temperatures in the upper 60s to lower 70s. Up in the NW mtns,
early rain will take a short break before additional forcing
arrives. The SHRA don`t look especially heavy, and Storm total
QPF there is <1.00". Continued moisture influx in advance of the
cold front will bring PWAT up to 1.5-1.75". Soundings are
unidirectional in the NW half of the CWA, and CAPE close to nil.
However, some hints of instability exist in the aftn and early
evening. So, a slgt mention of TSRA is OK there. Farther SE, the
NAM is rather optimistic with the QPF/TSRA than the GFS. GEFS
guidance has a very low chc of 1" QPF for much of the area. If
there will be any decent instability over the CWA it would be in
the SE where some heating (dependent on cloud cover/thickness)
could bring -2 LIs depending on your model of choice.

In general, the cold front should be into the central mtns by
midnight, and pushing past LNS around 12Z. Along and behind the
cold front, northerly winds will get rather gusty over the
Allegheny Plateau. Good dry advection will bring the dewpoints
down into the L40s at BFD by sunrise.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
In the wake of the cold front, an anomalously strong high
pressure system will usher in the coolest airmass of the season
to date. 1.5" PWATs ahead of the front will be replaced with
0.25" PWATs in its wake, supporting abundant sunshine, much
cooler temperatures and the first prolonged stretch of fall-like
weather.

A few lingering showers in southeast PA Wednesday morning will
quickly be replaced by clearing skies and plummeting dewpoints.
Conditions look rain- free for the end of the week, given the
likely advance of a very dry air mass across the eastern U.S.
Especially by Thursday, minimum RH within this type of air mass
should efficiently drop as low as 25-35%, perhaps even locally
lower. At this early juncture, surface winds should be dropping
off by Thursday, owing to the approach of a surface ridge axis,
but this timing will have to be watched for fire weather
concerns.

Fairly strong low-level cold advection is likely later Wednesday
into Thursday under a deep NW flow aloft over PA. This,
combined with clear skies and slackening winds in the overnight
hours will provide an ideal setup for radiational cooling.
Widespread frost is expected across much of Central PA, with the
exception of the southeast. Confidence in temperatures falling
below freezing across the northern tier continues to increase
and a Freeze Watch may be needed at some point. Temperatures may
be a degree or two colder on Thursday night as the surface high
remains centered over the northeastern United States.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
By this weekend, the large-scale flow at least temporarily is
progged to amplify, with a building upper ridge axis over the
central CONUS and south-central Canada, and the potential for a
trough axis along the east coast. Clustering analyses with the
mid-level height fields show a piece of short-wave energy
topping the aforementioned and upstream upper ridge as holding
the key. One solution keeps this wave more progressive over
eastern Canada, with less troughing along the east coast and
drier weather for PA, while an alternate scenario digs this same
wave down into the Mid-Atlantic, with the potential for a
closed low along the coast and at least somewhat higher rain
chances for parts of the Commonwealth. Given relatively equal
model membership between these two scenarios, each are about
equally likely from this early vantage point, and thus we have
low chances (20-30%) for showers indicated.

In either scenario, easterly flow in Central PA should support a
cold air damming scenario and persistent near to below-average
temperatures through the weekend. It will be ideal conditions
for any fall-themed activities and festivals around the
Commonwealth.

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
Mid-to-high level clouds are beginning to stream into the
western fringes of central Pennsylvania as of 06Z, with VFR
conditions continuing in the near-term. A showers stationed
along a KMGW-KHLG line will begin to enter the forecast area
over the next hour, bringing some rainfall to portions of the
Laurel Highlands closer to the 08-09Z timeframe. No restrictions
expected at this point with current observations at KMGW
outlining a scattered cloud deck with light rain potentially
dropping visibility closer to 6SM. Fog potential across the
eastern airspace (IPT/MDT/LNS) is the bigger concern in the
near-term; however, the best signals for fog formation remain
out of the airfields and more so along the I-81 corridor into
sunrise. Low probability (~20-30%) in any restrictions at
IPT/MDT/LNS keep mentions out of the TAF package, with
GLAMP/RAP/HREF guidance also keeping mentions out at this time.

First widespread rain in quite a while begins to enter western
Pennsylvania closer to sunrise (~12-13Z Tue) with BFD likely
(~90% confidence) to experience multiple hours with -RA. Clouds
begin to thicken soon after, leading to deterioration generally
west-to-east after 15Z Tue. Precipitation mentions in the 06Z
TAF package are weighted heavily towards HREF/GLAMP guidance
based on current observations/radar with more uncertainty with
regards to the ceiling forecast. A quick transition from MVFR
towards LIFR conditions is expected, but there remains some
timing differences, thus have stuck closer to GLAMP guidance
with respect to these drops, which does show some modest
agreement with the most recent NBM guidance. The 06Z TAF package
also brings first TSRA mentions, with PROB30 groups across
UNV/IPT where there remains some elevated instability laster
this afternoon. A non-zero chance of TSRA remains at BFD later
this morning (closer to sunrise, uncertain with respect to how
much instability there will be to play with) and at MDT/LNS
(after sunset, thus lowering instability makes TSRA mentions
less certain), thus have left mentions out at this time.

Outlook...

Thu...AM fog then VFR.

Fri-Sat...AM fog, otherwise clear with VFR conditions.

&&

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

&&

$$

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