022
FXUS61 KCTP 130326
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1026 PM EST Sun Jan 12 2025

.SYNOPSIS...
Low pressure over the Great Lakes will track north of Pennsylvania
through Monday, allowing milder air at the surface and aloft to
stream into the region. A cold front will push east through the
state on Monday. A deep upper level trough will then swing
over the region during the middle of the week. The trough will
lift out late in the week, likely followed by a cold front
passage next Saturday.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Bkn-ovc altocu/altostratus covering central PA late this
evening and through the overnight. Warm advection may eventually
moisten the boundary layer sufficiently in the pre dawn hours
to support snow flurries or even some patchy drizzle where cloud
seeders are lacking, but given patchy nature of this will
continue to be watched into Monday morning. Mins will range
through the 20s with some spots dipping into the upper teens
where the clouds thin sufficiently.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Main story heading from early through midweek will be a return
to sharply colder conditions. A closed upper low tracking into
the Upper Grt Lks will push a moisture- starved cold front
through Central PA Monday. Shallow cloud depths inferred by
model soundings suggest the possibility of -fzdz early Monday
morning. The strongest large scale forcing Monday, as inferred
by model 500-300mb qvec convergence fields, is progged to pass
north of PA, so any snow showers accompanying the front should
be very light and confined mainly to the Allegheny Plateau.
Ensemble mean qpf supports snow accumulations over the Allegheny
Plateau of <1 inch.

A southwest flow and surging warmth ahead of the front should
result in slightly above average max temps Monday based on the
latest GEFS 2m temp anomalies. A WSW boundary layer flow behind
the front should keep developing lake effect north of the border
Monday evening into most of Tuesday.



&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
The story remains the same through the extended period, as arctic
air puts the region back into the deep freeze from midweek
through next weekend. MinTs Monday night into Tuesday morning
and Tuesday night into Wednesday morning will be in the single
digits across the Laurel Highlands to the near 15 across the
Lower Susquehanna Valley. Winds will remain breezy- to- gusty
throughout the entirety of the middle of the week, with highest
wind gusts collocated with the coldest temperatures. This will
allow for wind chills to generally range from the negative
single digits across the western half of the area to single
digits across the Lower Susquehanna Valley. Looking at a
combination of ENS/GEFS/GEFS ensembles, over 60% of members
outline the potential for wind chills dropping below
-10F Tuesday morning across portions of Somerset and Cambria
Counties. There remains some potential for southern Clearfield
County to reach this criteria; however, lower confidence on this
solution given lower wind potential further north. Recent LREF
guidance does outline lower potential for wind chills dropping
below -10F, with Somerset County outlining the highest subset of
ensemble members (~40-50%) with this solution.

Latest NBM guidance results in wind chills approaching 10 below
zero over the ridgetops of the Laurel Highlands by Tuesday
morning. 850mb temp anomalies of around 9C below climo, combined
with plenty of stratocu, will result in highs temps Tuesday
ranging from just the teens over the Alleghenies, to the mid 20s
in the Susq Valley. Boosted wind gusts on Tuesday above NBM
mixing in about 15 percent of the 90th percentile winds. Given
some remaining uncertainty on temperatures/winds, have continued
mentions in HWO; however, want to note increasing confidence on
the potential for bitterly cold wind chills Tuesday morning and
to a lesser extent Wednesday morning. Wind chills on Tuesday
will struggle to surpass zero over the Alleghenies and 10F over
the Susq Valley. Veering boundary layer flow behind the exiting
shortwave will likely result in developing lake effect snow over
the NW Mtns Tuesday night.

Cyclonic flow will continue to generate lake and orographically
enhanced snow showers over the western and northern Alleghenies
Wednesday and Thursday. Have increased PoPs considerably in
this timeframe, using a NBM/CMCreg blend, towards Chc across
Warren/McKean Counties with SChc across the western highlands
throughout a majority of the period. Winds shift more westerly
late Wednesday, which will brining highest chance of PoPs to NW
PA in this timeframe. Snow squall potential, with the arctic
frontal passage, exists late Tuesday into early Wednesday
morning; however, confidence on this solution remains slightly
low at this time due to some model differences on timing.
Snowfall amounts in the Tue-Wed timeframe will be highest across
NW PA, where upwards of 3-4" are the most plausible solution
across NW Warren with localized higher amounts. Have not opted
for any Lake Effect products due to the prolonged light snow
ahead of and behind the heavier lake effect period; but have
continued to outline mentions in the HWO.

Temperatures will begin to moderate (slightly) on Friday and
Saturday with the bulk of the CWA reaching above the freezing
mark for MaxTs on Saturday. The reprieve from colder
temperatures will be short-lived;however, as surface low-
pressure approaches the area and brings a renewed shot of
precipitation to the region. Precipitation type with the
weekend system will be more tricky with temperatures near/above
freezing at onset, thus a period of rain will remain possible
especially across the southwestern zones while a wet snow could
mix is expected to mix in with rain across western/northern PA.
There is a non-zero chance at some freezing rain with model
soundings outlining a slight warm nose across the Endless
Mountains; however, given lower confidence at this time have
decided to nix mentions out of this forecast package.

&&

.AVIATION /03Z MONDAY THROUGH FRIDAY/...
VFR conditions will continue until midnight with light southerly
flow overnight. A deck of MVFR clouds is drifting across Ohio
and moving into western PA this evening, which will bring
restrictions to BFD around midnight and JST toward daybreak. VFR
will prevail elsewhere overnight.

IFR ceilings are favored (60% chance) at BFD between about 08Z
and 16Z as the cold front sweeps through and westerly flow
develops behind it. At JST, there is a similar chance (~60%) of
IFR ceilings over a shorter window around daybreak. Brief MVFR
restrictions are possible at AOO, UNV, and IPT as the cold front
traverses the region, with the most enduring restrictions
expected at UNV. Light snow could create visibility reductions
at BFD and perhaps JST, but widespread/long-lasting reductions
elsewhere are unlikely at this time.

In the wake of the front, west winds could gust 20 to 30 kts
Monday afternoon across the north and west, with locally higher
gusts possible at JST and AOO. The biggest forecast uncertainty
at this point is the duration of restrictions at airfields in
the central ridge/valley region (JST, AOO, UNV, and IPT). In
this pattern, enduring MVFR is most likely at JST, but there are
some indications that clouds could scatter out with VFR
conditions developing as early as 18Z. Farther east, if a band
of snow showers develops along the cold front, a brief period of
IFR cannot be ruled out. On the other end of the spectrum, if
the system trends drier, the deck of MVFR ceilings could scatter
out as it crosses east of the mountains and lead to VFR
throughout the TAF period.

Outlook...

Mon-Wed...Snow showers/tempo IFR vsbys possible W Mtns. Gusty
west wind Tuesday.

Thu...Mainly VFR. A weak warm front, then cold front moves east
across PA with very limited moisture and likely just some
flurries or perhaps scattered -SHRA, with brief vsby reductions
across the Northern and Western Mtns.

Fri...VFR expected, showers possible late.

&&

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

&&

$$

SYNOPSIS...DeVoir
NEAR TERM...DeVoir
SHORT TERM...DeVoir/Fitzgerald
LONG TERM...DeVoir/NPB
AVIATION...Banghoff