108
FXUS61 KCTP 221627
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1127 AM EST Fri Nov 22 2024

.SYNOPSIS...
* The first winter storm of the season will bring heavy snow to
  the higher terrain in north central Pennsylvania and the
  Laurel Highlands today into tonight
* Improving conditions over the weekend, followed by some rain
  on Monday
* Another bout of winter weather could impact Holiday travel
  heading into Thanksgiving Day

&&

.NEAR TERM /UNTIL 7 PM THIS EVENING/...
Elevation dependent snow storm continues over central PA. Reports
of 8-12 inches of snow in the higher terrain across Tioga and
Sullivan Counties with multiple trees/power lines down and
several roads closed. We were keen to adjust storm totals higher
for these zones (max around 15" in Sullivan Co) and be more
definitive (will not could) in regards to [weight of] snow
damage impacts. Heavy snow band continues to wrap westward
approaching the Endless Mtns per BGM radar.

Hires models suggests a weakening trend with the northeast PA
banding this afternoon with focus shifting to combined lake
enhanced+upslope snow continuing to impact the Laurel Highlands.
We added near blizzard conditions at times for this area with
prolonged visby between 1/2-1/4 mile at KJST/K2G9 and persistent
wind gusts between 25-35 mph.

As temps slowly rise and precip rates fade off with time, we
trimmed back the end time of the winter wx advisory to 4pm
across the NW Alleghenies and central ridges along the I80
corridor. The lower elevations/valley locations are seeing very
little to no additional accumulation, while ridgetops near or
above 14-1500ft could pick up a slushy coating up to 2 inches
before snow tapers off by this evening.

The only headline in effect after 4pm today will be the winter
storm warning for the Laurel Highlands.

&&

.SHORT TERM /7 PM THIS EVENING THROUGH 6 PM SATURDAY/...
Diminishing precipitation is expected in general late Friday
into Friday night, as the upper low lifts out. However,
lingering lake effect will affect the W Mtns. Forecast thermal
profiles moderate with the departure of the upper low to the
point that lake effect snow showers may mix with rain over the
Alleghenies Friday night.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
* Winter Weather with a light to moderate snow accum could Impact
  Travel on Thanksgiving Day

One last channel of vorticity stretched out to the west of the
center of the upper low will enhance lift on Sat along the
western mtns. That will help precip (mainly rain) linger over
the western hills. It`s a high-PoP but low QPF event. This light
precip will dwindle Sunday AM, as subsidence inversion height
fall and high pressure approaches from the Tennessee Valley.
Milder conditions (+3 to 6F vs Sun) look likely for Monday. A
fast-moving but compact system will develop very quickly as it
near from the OH valley, and pass across the state Monday-Monday
night. Temps should remain mild enough to be almost all rain
except on the very highest (>2000ft) elevations. No accums are
expected at this point, but a slight timing change (time of
day/night) may allow a slushy coating. Tues looks mainly dry
under high pressure. Perhaps a SHSN NW.

The next 2 days (peak travel Wed and Thanksgiving Day itself)
seem highly uncertain. Cold LLVL air residing north of the
Mason/Dixon line combined with a zonal WSW jet aloft across the
ern 2/3rds of the CONUS will likely lead to a fast, progressive
flow.

The front that pushes SE across the commonwealth Mon night will
stretch out West to East to the south of our latitude, and
moisture should start to return and pool up along it on return
flow from the GOMEX.

Timing of support/forcing from the west is highly uncertain.
GFS Ensembles have low spread in 5H and thickness plots, with a
very, very dip/trough developing to our west mid- week. 00Z
ECMWF is much (1 day) slower with generating a sfc low and
making precip arrive in PA (not until Turkey Day), vs the GFS
which is faster. Thermal profile for the start of any precip
either Wed or into Thurs would likely be cold enough over some
(nrn) portion of the CWA to make frozen or freezing precip.
Following the NBM`s very slow building/ramp up in PoPs without
any notion of support for deviation at this point. Just not
enough strong points to make any precip arrive slower or faster.
Be prepared for slippery/poor travel during this upcoming long
holiday travel time.

&&

.AVIATION /16Z FRIDAY THROUGH TUESDAY/...
Snow will continue to overspread the area this morning with
reduced visibility accompanying it and subsequent lowering of
ceilings to IFR areawide. The main uncertainty in the forecast
is in regard to precip type. Snow will be the predominant
precip type into early afternoon at all sites, but model
soundings suggest that rain will begin to mix in everywhere
except BFD and JST after 18Z. The exact timing of this
changeover will impact how long visibilities remain below 1
mile. Even if visibilities rise above IFR, ceilings are expected
to stay below 1000ft areawide through at least 00Z.

Wind gusts will increase this morning with gusts of 25 to 30
knots likely throughout the day. Gradual improvement is
expected tonight as the center of low pressure moves offshore.
Lingering upslope/lake enhanced clouds and occasional showers
will keep IFR or LIFR conditions at BFD and JST overnight, but
MVFR to VFR conditions are expected farther south and east.

Outlook...

Sat...Periodic restrictions in rain and snow showers, mainly
across the mountains (KBFD and KJST). MVFR much of the time for
KUNV/KIPT/KAOO. Mainly VFR at KLNS and KMDT. Continued breezy.

Sun-Mon...Lingering restrictions possible at KBFD and KJST,
otherwise mainly VFR.

Tues...MVFR cigs/isold SHSN NW, VFR SE.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 4 PM EST this afternoon for
PAZ004-005-010>012-017>019-025-034-045-046-049-051-052.
Winter Storm Warning until 4 PM EST this afternoon for PAZ006-
037-041-042-053-058.
Winter Storm Warning until 7 AM EST Saturday for PAZ024-033.

&&

$$

SYNOPSIS...Steinbugl
NEAR TERM...Steinbugl
SHORT TERM...Lambert/Fitzgerald/Bowen
LONG TERM...Lambert/Dangelo
AVIATION...Banghoff/Bauco