983
FXUS61 KCTP 240420
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1120 PM EST Sat Nov 23 2024

.SYNOPSIS...
* Breezy with showers over the western Alleghenies into Sunday
* Rain returns Monday night followed by gusty winds and lake
  effect snow showers into Tuesday
* Mix of rain and snow possible for Thanksgiving Day followed by
  colder than average temperatures into the holiday weekend

&&

.NEAR TERM /UNTIL 7 AM SUNDAY MORNING/...
A seasonally chilly northwest flow and relatively mild lake
water, combined with the passage of a couple of weak shortwaves,
should continue to support light lake effect rain showers/sprinkles
tonight across the Allegheny Plateau. Low inversion heights and
downsloping flow should result in a dry night to the lee of the
Alleghenies.

Mainly cloudy skies and only weak low level cold advection
should result in slowly falling temps overnight, with readings
at dawn likely ranging from the mid 30s over the higher terrain
of the Alleghenies, to the low 40s across the Susq Valley.

&&

.SHORT TERM /7 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
Near term models all shift the focus of lingering lake effect
rain showers/sprinkles from Clearfield County at dawn to the NW
Mtns by afternoon, as surface ridging works in from the Ohio
Valley. Falling inversion heights should result in brightening
skies across the southern part of the forecast area as the day
progresses, especially where the westerly flow downslopes into
the Lower Susq Valley.

A ridge of high pressure building into the region tonight
should result in mostly clear skies and light winds in the south
and breaking clouds over the northern counties. Latest SREF and
NAMNest indicate patchy valley fog is likely across primarily
the N and W Mtns.

Models in good agreement spreading scattered rain showers into
the western part of the forecast area Monday afternoon, as a
30kt southwesterly low level jet and associated plume of
anomalous pwats work into the state ahead of an upstream trough.
However, partly to mostly sunny skies to start Monday, combined
with warm advection ahead of the trough, should support high
temps several degrees above average with most locations reaching the
50s.

Strong large scale forcing and a decent plume of pre-frontal
pwats supports high POPs Monday night into early Tuesday
associated with the cold front passage. Can`t even rule out a
rumble of thunder in spots early Tue AM based on some minimal
cape noted in the latest guidance. Most likely rain totals based
on the 18Z EPS is around a quarter inch.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
* Winter Weather may impact travel on Thanksgiving Day across
  Central PA

The cold front and any associated rain showers should exit the
eastern edge of the forecast area by around midday Tuesday.
Large scale subsidence behind the front should result in
blustery conditions with breaking clouds over most of Central
PA. A progged west-southwest boundary layer flow should keep
developing lake effect snow showers north of the border.

Bufkit soundings support wind gusts of 30-35kts Tuesday with a
marked ramp up between 12Z-16Z with the passage of a fairly
strong isallobaric couplet. Max temps in the mid 40s to mid 50s
should occur around midday, with cold advection causing readings
begin falling during the afternoon.

Fair weather and light winds look likely Wed, as surface
ridging builds across the state. Although thickening high clouds
are possible in the PM hours ahead of an area of low pressure
approaching from the Miss Valley.

All medium range model guidance tracks an area of low pressure
northeast from the Lower Miss Valley late next week, likely spreading
precipitation across PA for Thanksgiving Day. There remains plenty
of uncertainty inherent in a day 5 forecast regarding the exact
surface low track and resulting ptypes. However, a large
majority of ensemble members support a moderate precipitation
event late Wed night through Thursday with mean qpf around a
half inch. Lack of a blocking high suggests any snow may be
confined to a relatively narrow corridor on the northern edge of
the precip shield. Early thermal profiles indicate the best
chance for a few inches of snow will be over the N Mtns, with
all rain likely near the Mason Dixon Line.

Blustery and cold conditions with lake effect snow showers
over the W Mtns look very likely Friday and Saturday, as upper
level trough pivots across the region.

&&

.AVIATION /04Z SUNDAY THROUGH THURSDAY/...
NW flow pattern will continue through the next 24hrs, through
the 24/00Z TAF cycle. This translates to high confidence IFR at
KBFD/KJST, MVFR at KAOO/KUNV and lower end VFR elsewhere.
Continued breezy with sfc wind gusts from 270-310 degrees
20-30kt, though decreasing overnight. We anticipate some
marginal (1 flight category) improvement by Sunday afternoon
with showers fading over northwest PA. Expect MVFR to VFR cigs
with sfc wind gusts 20-25kt from 270-300 degrees.

Outlook...

Mon-Tue...Strong CFROPA Monday night with widespread rain and
potential LLWS followed by strong winds and snow showers over
the western half of the airspace.

Wed...Not as windy with pcpn ending and MVFR to VFR cigs; mixed
precip could reach the southwest airspace by 12Z Thu.

Thu...Increasing likelihood of widespread IFR in mixed precip
especially across the southern half of PA.

&&

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

&&

$$

SYNOPSIS...Steinbugl
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald
LONG TERM...Fitzgerald
AVIATION...Steinbugl/Gartner