425
FXUS61 KPBZ 010813 CCA
AFDPBZ

Area Forecast Discussion...CORRECTED
National Weather Service Pittsburgh PA
313 AM EST Mon Dec 1 2025

.SYNOPSIS...
Dry and cold weather is expected during the Monday daylight
hours under high pressure. The next system brings widespread
precipitation late tonight through Tuesday morning, with
impactful snow accumulation in much of the region. After a brief
break Tuesday night into Wednesday, an active weather pattern
and below-normal temperatures continue into next weekend.

&&

.NEAR TERM /THROUGH TODAY/...
KEY MESSAGES:

- Snow showers/flurries near and north of Pittsburgh mostly
  ending by sunrise
- Light winds and dry weather today under high pressure
---------------------------------------------------------------

The axis of a 500mb shortwave is currently swinging across the
Upper Ohio Valley. The associated surface trough is providing
some low-level convergence, which along with marginal moisture
is producing flurries and a few snow showers to the north of
Pittsburgh. Moisture does not extend too far into the DGZ, which
will help to limit intensity. Still, with snow-to-liquid ratios
in the neighborhood of 16-17 to 1, a localized inch or so
remains possible mainly north of I-80, with a localized dusting
possible elsewhere. By sunrise, lowering inversion heights and
the departing shortwave will bring most of this activity to an
end. West-to-northwest wind should slowly diminish with time,
with gusts of 20 MPH easing towards morning.

High pressure will then pay a brief visit to the Ohio Valley
during the daylight hours, providing a dry and chilly day with
temperatures remaining around 10 degrees below normal. Some
peeks of sun are possible in the morning as stratocumulus break
up, but clouds should thicken once again this afternoon ahead of
the expected winter weather system.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...
KEY MESSAGES:

- Widespread precipitation returns late tonight and continues
  through Tuesday morning
- Mostly snow north of I-70; some icing possible to the south
  and in the ridges
- Impactful snow accumulation centered on the Tuesday morning
  commute in many areas
- Dry and cold Tuesday night and Wednesday
----------------------------------------------------------------

The next shortwave trough, positioned over the Upper Midwest at
00Z Tuesday, will swing into the Middle Ohio Valley by Tuesday
morning and cross into the Appalachians by evening. Models
continue to agree on the track of a surface low through coastal
GA/SC late tonight, and then tracking it up the Eastern Seaboard
to a position just south of Cape Cod by 00Z Wednesday. This
track still presents some precipitation type issues, mainly in
the ridges and some locations south of I-70. However, much of
the region should see mostly snow from this system, with
impactful accumulations quite likely.

Precipitation will begin to arrive in earnest towards midnight
and should overspread the region by 09Z or so. Most locations
should begin as snow. Models continue to be most aggressive with
850mb warm advection south of the Mason-Dixon Line and up the
spine of the Laurels. It is here where freezing rain is most
likely, and in a related sense, where snow-to-liquid ratios will
remain lower. Icing of a light glaze is expected in spots here,
perhaps up to 0.10 inch in portions of the WV ridges. Further
west and south of I-70, warming is not as strong, and as such,
freezing rain should be spottier, with perhaps isolated
instances of sleet where melting aloft is less complete. All in
all, portions of the Monongahela Valley into northern West
Virginia may see the lowest snow totals from this event, with
even some rain mixing in by the tail end.

North of I-70, snow accumulations in the 3 to 5 inch range
continue to be suggested with storm total liquid equivalent in
the 0.20 to 0.40 range and SLRs in the range of 10:1 to 14:1.
NBM probabilities for 3 inches or more are generally in the 50
to 70 percent range across most of this region, lower generally
south of the WV/PA border. The HREF continues to suggest
occasional maximum hourly snowfall rates in the 0.5 to 1.0 inch
range during the predawn hours, at a time when jet-aided support
for vertical motion is maximized, and also when frontogenetically
forced banding is possible. Neighborhood probabilities for
1"/hour rates get into the 30-50 percent range at times for much
of the region between 4 AM and 9 AM, which of course
incorporates the Tuesday morning commute.

Considering all of the above, a Winter Weather Advisory has been
issued for the entire forecast area from midnight to 1 PM
Tuesday. Much of the region will see the 3 inch snow criteria,
while some locations that do not are expected to see at least
light icing. In all cases, with the peak impact and
precipitation rates likely to be seen during the morning
commute, an Advisory is justified even if ice/snow
accumulations come in below criteria.

Steady precipitation will wrap up from west to east during the
late morning and early afternoon as the surface low races into
the Atlantic. Precipitation may linger longest near and north
of I-80 as well as in the ridges with a brief push of NW flow,
but additional accumulation should not be as impactful. Backing
wind will bring any lingering activity to an end by 00Z
Wednesday.

Dry and chilly weather is forecast for the bulk of Tuesday night
and Wednesday as surface ridging once again visits the Upper
Ohio Valley. Areas near and south of Pittsburgh stand the best
chance of seeing a fair bit of sunshine by the afternoon hours.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
KEY MESSAGES:

- Active pattern continues
- Precipitation chances for Wednesday night/Thursday, as well as
  Friday into the weekend
- Below normal temperatures through the period
-------------------------------------------------------------------

During the day Wednesday, surface low pressure deepens over the
northern Great Lakes and traverses eastward through Ontario and
Quebec. This will drop a cold front through the region
Wednesday night and Thursday with a reinforcing shot of cold air.
Associated precipitation looks to be mostly snow, but moisture
appears limited, and the best synoptic support remains off to
our north. The NBM shows areas north of I-80 with a 30 to 40
percent chance of getting an inch of snow from this system, with
lower chances to the south.

Another brief dry interlude under high pressure is possible Thursday
night into early Friday before another system is expected to
climb from the Gulf Coast to the Eastern Seaboard. Once again
the exact track of this system will determine exact precip type
and snowfall amounts, but at this time it looks like wintry
weather could be with us to end the work week and begin the
weekend.

Temperatures are likely to remain below average throughout the
period. Daytime highs in the low to mid 30s are figured through
Friday, before some slight moderation by next weekend.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
Gusty winds, now to around 15kt, will continue to diminish
through the early morning hours. Light snow continues early this
morning with a crossing shortwave, primarily north of I-80 (FKL,
lower impact at DUJ). This should taper off through sunrise.
Otherwise, MVFR ceilings remain likely areawide, scattering to
VFR late morning into the early afternoon.

Another low pressure system will impact the region tonight into
Tuesday, bringing a round of widespread snow to the area and
mixed precip for the Mon Valley. Heaviest snowfall is expected
to occur during the 06-12z Tuesday timeframe, and may feature
one or more narrow SW/NW oriented bands within the broader snow
shield. There is a roughly 30-50% probability for rates within
these bands to exceed 1 inch per hour.

Outlook...
Widespread snow should end later Tuesday morning with gradual
ceiling improvement into Wednesday. Additional light snow chance
is expected Thursday, favoring locations north of PIT.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Winter Weather Advisory from midnight tonight to 1 PM EST
     Tuesday for PAZ007>009-013>016-020>022-029-031-073>078.
OH...Winter Weather Advisory from midnight tonight to 1 PM EST
     Tuesday for OHZ039>041-048>050-057>059-068-069.
WV...Winter Weather Advisory from midnight tonight to 1 PM EST
     Tuesday for WVZ001>004-012-021-509>514.

&&

$$

SYNOPSIS...CL
NEAR TERM...CL
SHORT TERM...CL
LONG TERM...AK/CL
AVIATION...Rackley

Corrected long term header