658
FXUS61 KCTP 071019
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
619 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 /10Z TUESDAY THROUGH SATURDAY/...
Mid-to-high level clouds continue to stream into central
Pennsylvania as of 10Z, with VFR conditions expected to begin
trending downwards across our western airfields in the 12Z-18Z
timeframe. Showers across western Pennsylvania is expected to
begin at BFD closer to the 12-13Z timeframe; however, current
observations underneath the radar returns outline continued VFR
conditions. At this time, not seeing any signals that outline
sub-VFR conditions with that batch of showers, so continuing to
outline VFR conditions through ~14Z where model guidance
outlines fair agreement in the onset of sub-VFR conditions at
BFD, with JST/AOO likely following +2-3hrs. Rainfall will
gradually continue overspreading the area, reaching the eastern
airfields (IPT/MDT/LNS) closer to the 20Z Tue to 00Z Wed
timeframe with moderate (50-60%) confidence on timing.

Recent model guidance outlines IFR is the floor at all
airfields outside of BFD/JST throughout the 12Z TAF package;
however, there will remain a non-zero chance of LIFR conditions
at all airfields in the 06-12Z Wednesday timeframe. Model
guidance continues to struggle with where thunderstorms (more
limited in recent guidance and struggling more with placement)
and heavy rain develop, thus have nixed mentions of TSRA in the
12Z TAF package due to lower (~10-20%) confidence in any impacts
at the airfields.

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