690
FXUS61 KCTP 070606
AFDCTP

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

.SYNOPSIS...
* Showery weather will cross the Commonwealth later tonight
  through early Wed morning, associated with an incoming cold
  front
* Breezy and Chilly for Wednesday morning as the rain ends
* Drier and much cooler weather for Wednesday afternoon through
  Saturday

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Patchy mid and high clouds were drifting across the region this
evening. Clouds will increase/thicken up from the SW late
tonight/early Tuesday 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.

Temps ranging from the mid 60s across the NW Mtns to the low
70s (SE) will fall another 8-10 deg F then flatten out to a
large extent aft 07Z.

Latest hi res guidance shows some spotty light showers drifting
across NW half of the CWA after 07Z with more numerous showers
or even steady light rain entering the NW and WCentral Mtns of
the state around 11-12Z Tuesday.

Previous Disc...

Tongue of best moisture dosen`t arrive in the NW until morning.
But, there is a little lift aloft in the late night and early
morning hours in the W. So, many people should get wet over the
wrn mtns around sunrise. Amounts will be very minor. PoPs will
be OK in the 30s around JST-UNV line before sunrise, and 60+ for
the NW mtns. Stability is rather high, so we will keep TSRA out
of the forecast for the overnight.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/...
Much of the day SE of AOO-UNV-IPT will be fair and very warm
(again). Clouds will get thicker in the aftn. 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 front should be into the central mtns by
midnight, and pushing past LNS around 12Z. Tried to put some
timing in the gridded PoPs. The cloud cover in the NW half of
the area has a strong possibility to keep temps below NBM
guidance. Have nudged the maxes down there by 1-3F. Kept TSRA
chcs where the NBM has them as instability looks limited. Wind
gets gusty after FROPA over the Allegheny Plateau. Good dry
advection will bring the dewpoints down into the L40s at BFD by
sunrise.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
For the latter part of the work week (Wednesday through Friday),
there is reasonably high confidence that a surface cold frontal
passage early Wednesday will be progressive in nature, pushed on
by a kicker northern stream short-wave trough in the upper
levels of the atmosphere. This should limit clouds and any
lingering showers to early in the day Wednesday, with
improving/clearing conditions by afternoon.

From Wednesday afternoon through Friday, conditions look rain-
free, 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.

By next 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.

&&

.AVIATION /06Z 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...Lambert/Dangelo
NEAR TERM...Lambert/Dangelo
SHORT TERM...Lambert/Dangelo
LONG TERM...Jurewicz/Bauco
AVIATION...NPB