247
FXUS61 KCTP 240119
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
819 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 Lower 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

Tuesday looks mainly dry with high pressure building in. A
tightening surface pressure gradient will support gusty
westerly winds, perhaps approaching 30-40kts. A snow shower or
two is also possible in northwest PA.

Wed now looks fairly good for travel across PA with ridging
building over the state. A bit of lingering lake effect snow
is possible over the NW Mtns early in the day. Much of the
medium range model guidance tracks an area of low pressure
northeast from the Lower Miss Valley late next week, spreading
precipitation across PA for Thanksgiving Day. There still
remains a spread in the models, signaling significant
uncertainty in precipitation type. The ECMWF has remained
consistent with the track of the low the last few runs,
bringing colder air and a more snowy solution. GFS is still
signaling a weaker low with mainly rain for our precipitation.
For now a rain/snow mix has been included for Thanksgiving day,
but overall confidence is increasing for hazardous travel
conditions.

Current timing and placement of mass features should allow for
gusty winds and drying on Friday except in the northern
Alleghenies where the cold air and WNW flow will generate
lake effect SHSN which may linger thru much of next weekend
(days 7-9). A shot of even colder air comes along late in the
weekend, and looks like a pattern favorable for snow squalls.

&&

.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
NW flow pattern becoming firmly entrenched over the next 24hrs
through the 23/18Z 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 decreasing late tonight. 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/Steinbugl
LONG TERM...Fitzgerald/Bowen
AVIATION...Steinbugl