253
FXUS61 KPBZ 022305
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
605 PM EST Tue Dec 2 2025

.SYNOPSIS...
Drier weather expected tonight through Wednesday, followed by
additional snow chances and below-normal temperatures through
the end of the week.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
KEY MESSAGES:

- Winter Weather Advisory extended until 10 PM EST for the
  ridges of southwest PA and northern WV.
- Additional light snow and ice accumulations possible in the
  ridges through evening; precipitation ending elsewhere.
- Refreezing on untreated surfaces could cause slick spots and
  hazardous travel overnight into Wednesday morning.
---------------------------------------------------------------

Accumulating precipitation has ended across most of the local
area as a cold front brings dry air in from the northwest.
Initial reports indicate a widespread 2 to 5 inches of wet snow
fell across the region. Aside from occasional light flurries
(with no additional accumulation), dry weather prevails for much
of the area through the rest of the period. There are two
lingering concerns for the near term, which are discussed in the
paragraphs below.

The first concern is for light ice accumulations to continue in
the Laurels and WV ridges through this afternoon and evening.
While precipitation is ending across lowland areas, hi-res model
soundings indicate shallow moisture remaining trapped near the
surface in a layer that falls between 0C and -10C. This
saturation, combined with weak upslope-induced ascent, will
support the formation of supercooled water droplets in that
layer. Given a lack of ice crystals or nuclei to freeze on (and
the fact that heterogeneous nucleation and deposition are most
common at temperatures colder than -10C), these droplets are
most likely to coalesce and fall as freezing drizzle. Some mix
with light snow is possible since the moist layer reaches -10C,
but additional snowfall accumulations would remain at or under
an inch. However, even a light glaze of ice accumulation is
enough to justify a Winter Weather Advisory. Therefore, the
advisory has been extended in the ridges until 10 PM EST.

The second concern is the potential for refreezing tonight into
early Wednesday morning. Temperatures climbing slightly above
freezing this afternoon will support some melting of snow, but
dense/persistent cloud cover will act to mitigate
heating/evaporation from the sun. Any moisture that remains
(especially on untreated roads and sidewalks) will quickly
refreeze when temperatures drop into the 20s overnight, leading
to slick spots and hazardous travel conditions tonight and
Wednesday morning.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
KEY MESSAGES:

- Dry weather and below-seasonal temperatures Wednesday
- A front Wednesday night into Thursday provides a reinforcing
  cold shot and some minor snow accumulation mainly in the
  ridges and north of I-80
- Very cold temperatures Thursday night; single digits possible
  north of Pittsburgh
----------------------------------------------------------------

Surface high pressure crosses the Middle Ohio Valley and the
Central Appalachians later Tuesday night and Wednesday, and
extends ridging up into the forecast area. This should provide
dry weather and continued chilly temperatures. Highs on
Wednesday will continue to run some 10 to 12 degrees below
climatology.

The next cold front, extending from low pressure over Hudson
Bay, is forecast to cross the region late Wednesday night and
Thursday morning. The associated shortwave trough is expected to
remain mostly over the northern Great Lakes, keeping much of the
synoptic support to our north. Still, the boundary will provide
a reinforcing shot of cold air as 850mb temperatures drop into
the -10C to -15C range by Thursday afternoon. Given the system`s
northern origins, moisture remains limited overall. A shot of
light snow is forecast, with minor accumulation. Parts of
western PA south of I-80 and northern WV have a 30 to 50 percent
chance of exceeding a half inch (but a 20 percent chance or less
at exceeding an inch). Probabilities are locally higher in the
Laurels, owing to stronger lift with upslope enhancement, where
there is a 50 to 70 percent chance of exceeding a half inch and
a 30 to 40 percent chance of exceeding an inch. Additionally
portions of Mercer and Venango may be more favored for lake-
enhanced activity as model soundings hint at some modest
instability and reasonably steep lapse rates into the DGZ that
could support briefly stouter snow showers during peak heating.
Better potential for such activity, including snow squalls, lies
to the north with deeper moisture and instability, but those
areas north of I-80 could still see an inch or so of
accumulation before snow ends Thursday afternoon.

High pressure then builds into the region following Thursday`s
cold front, with temperatures Thursday night looking to be the
coldest of the week. The latest NBM suggests a70 percent chance
or greater of lows dropping below 20 degrees across the entire
county warning area. It also suggests a 40 to 60 percent chance
for single digits along and north of the I-80 corridor (20 to
40 percent chance in areas farther south).

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
KEY MESSAGES:

- Dry and cold Thursday night and Friday
- Below average temperatures and continued wintry precipitation
  chances into early next week
-------------------------------------------------------------------

Analysis of ensemble model clustering continues to favor broad
upper level troughing east of the Rockies Friday with an
embedded shortwave lifting fairly quickly through the Ohio River
Valley. These trends favor keeping the surface low track south
of the region, with only low probability for light snow clipping
locations south and east of Pittsburgh through the day. Passage
of the upper trough axis and surface cold front
Saturday/Saturday night may provide enough cold advection within
NW flow plus weak lift to create lower probability
precipitation chances that favor higher terrain and Lake Erie-
adjacent zones. Temperature is highly favored to stay below
average as the Saturday front only reinforces the recent
seasonably cool trends.

Eastern CONUS trough is likely to persist into early next week
with embedded shortwave movement driving precipitation chances.
Periodic but generally light precipitation chances could develop
while the cooler airmass generally maintains a snow
precipitation type.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
KEY MESSAGES:

-MVFR prevails through the first half of Wednesday
-Scattering to VFR expected in the afternoon
-Gradual wind shift from NW to SW
-------------------------------------------------------------------

Conditions have improved to MVFR across the board this evening
with the departure of snow. A lingering upper trough and NW flow
off of the Great Lakes is maintaining a few flurries, but no
observations have shown notable degradation in restrictions from
the overall broad 1.5-2.5 kft cigs. MVFR conditions will
prevail tonight and through tomorrow morning as low level
moisture remains in place beneath a sinking subsidence inversion
from approaching high pressure.

Said high pressure will briefly build in Wednesday with wind
backing to the SW around 8-10 knots. Improvement to VFR is
expected by afternoon as drier low level air advects in, though
mid-level moisture and associated cloud coverage will
concurrently increase ahead of the next approaching cold front
expected on Thursday.

Outlook...
Cig restrictions are likely, along with scattered snow showers,
late Wednesday night into Thursday with a crossing cold front.
VFR is expected to return late Thursday and Friday as high
pressure builds in behind the front. Restrictions are possible
again Saturday and Sunday with a crossing cold front.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Winter Weather Advisory until 10 PM EST this evening for
     PAZ074-076-078.
OH...None.
WV...Winter Weather Advisory until 10 PM EST this evening for
     WVZ510>514.

&&

$$

SYNOPSIS...Cermak/CL
NEAR TERM...Cermak/CL
SHORT TERM...Cermak/CL
LONG TERM...Frazier
AVIATION...WM/MLB