418
FXUS61 KPBZ 021159
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
659 AM EST Tue Dec 2 2025

.SYNOPSIS...
Widespread precipitation expected this morning, with impactful
snow accumulation for 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 TONIGHT/...
KEY MESSAGES:

- A Winter Weather Advisory remains in effect for the entire
  area until 1 PM
- Widespread snowfall accumulations of 2-5 inches, especially
  north of I-70. Heaviest snowfall rates occur between 4 AM and
  8 AM, impacting the morning commute
- Mixed precipitation in the Mon Valley and the ridges of SW PA
  and northern WV, including a chance for light ice accumulation
  due to periods of freezing rain
- Precipitation ends from west to east by late morning or early
  afternoon
---------------------------------------------------------------

Early Morning Update:
Widespread light to occasionally moderate snowfall is ongoing
across much of the area as of 630AM EST, with a wintry mix of
snow/sleet/freezing rain in the Mon Valley as warm air aloft
attempts to nose its way slowly northward. Snow accumulations
are on track with the forecast, with most early morning report
indicating between 1-3 inches having fallen across the region
thus far (locally up to 4 inches in spots). Numerical guidance
appears to have a solid handle on this event to this point and
continues to suggest accumulating snow ends from west to east
during mid to late morning hours, roughly the 8-9AM timeframe in
eastern OH, 9-10 AM in the lowlands of western PA and northern
WV, and lingering a little longer to around Noon in the ridges.
An additional 1-3 inches of accumulation will be possible
through that time.

Even after accumulating snow ends, a dense low cloud deck is
forecast to linger throughout the day so there won`t be much (or
any) sunshine to help melt snow and ice. Still, with high
temperatures climbing slightly above freezing, some melting may
occur on untreated roads this afternoon, but low temperatures in
the 20s tonight will pose a threat for refreezing and icy
conditions into Wednesday morning.

Previous Discussion:
Little change was needed to the forecast through today, as the
sequence of events is playing out largely as expected. An
upper trough, currently crossing the western Great Lakes, will
swing into the Middle Ohio Valley this morning and into the
Appalachians by this evening. Models continue to agree on the
track of the associated surface low, bringing it up the Atlantic
Coast today and to just off of southern New England by 00Z.
Precipitation is in the process of overspreading the region,
having begun here in Moon at about 0715Z.

Warm advection ahead of the system has led to rising
temperatures south and east of Pittsburgh, with LBE, MGW, and
VVS all rising into the mid 30s as of 2 AM. HRRR soundings here are
suggesting a weak warm layer aloft, or even near isothermal
profiles around 0C, suggesting perhaps some sleet or freezing
rain at onset, before wet-bulbing changes much of this over to
snow. Lower snow-to-liquid ratios (6:1 to 10:1) are expected as
compared to areas to the northwest. However, a stronger and
more persistent warm layer aloft remains more likely in the area
of the Laurels and especially the West Virginia ridges, where
freezing rain is more of a threat. Only a light glaze is
expected in most cases, but eastern Tucker County could see a
more meaningful ice accretion of a tenth of an inch or so this
morning. Some plain rain should even mix in by the tail end of
this event.

Otherwise, in areas west of I-79 and north of I-70, all snow is
forecast for the event, with SLRs generally in the 10:1 to 14:1
range. We are already seeing visibilities of a mile or less at
a few locations. The heaviest snow rates are still pictured to
be in the 4 AM to 8 AM window, creating widespread impacts
during the morning commute. The HREF continues to suggest that
instantaneous snow rates of 1 inch per hour remain possible in
banded precipitation in the overall shield, supported by 700mb
frontogenesis and jet-aided ascent. Storm total snowfall of at
least 3 inches has a 50 to 80 percent probability of occurrence
in the all-snow region, with lower probabilities in the mixed-
precipitation region to the south and east. Best probabilities
of 4 to perhaps 5 inches in spots, at around 50 percent, lie
northeast of Pittsburgh. Given all of this, sufficient impacts
to the morning commute are expected to justify the continued
existence of the CWA-wide Winter Weather Advisory, even if
accumulation criteria are not technically met in some locations
to the southeast of Pittsburgh.

Precipitation should end fairly rapidly from west to east
during the late morning and early afternoon as the low pulls
into the Atlantic and as moisture depth decreases with the
passage of the shortwave trough axis. Some snow showers may
linger 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, remaining under an inch. Trends will continue to
be monitored to see if a localized extension of the Winter
Weather Advisory could be needed, particularly in the ridges.

&&

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

- Mostly dry and cold Tuesday night and Wednesday
- A front Wednesday night into Thursday provides a reinforcing
  cold shot and some minor snow accumulation
----------------------------------------------------------------

Isolated snow showers may linger north of I-80 and along the
ridges in northwest flow, but slowly backing low-level wind and
falling inversion heights should help to largely shut off this
activity by midnight, with little additional accumulation.

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. Maximum values 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 quite minor accumulation. Areas
south of I-80 have a 30 percent or less chance of exceeding a
half inch. Portions of Mercer and Venango that may be more
favored for lake-enhanced activity could see an inch or so by
the time the snow cuts off Thursday afternoon. Here, 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. However, better potential for such
activity, including snow squalls, lies to the north with deeper
moisture and instability.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
KEY MESSAGES:

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

Dry weather is forecast for Thursday night and Friday as high
pressure crosses in quasi-zonal flow. A mostly clear sky and light
wind may aid radiational cooling on what looks to be the coldest
night of the season thus far. Many locations away from urban areas
and major river valleys have a 50 percent or greater chance of low
temperatures colder than 10 degrees according to the NBM. Below-
freezing high temperatures are expected Friday for many areas north
of I-70.

For Saturday, ensembles generally drag a weak 500mb shortwave across
the Upper Ohio Valley with a Great Lakes surface low. There are some
questions regarding precipitation type, but amounts appear to be
light overall. Some modest temperature recovery may occur, into the
mid to perhaps upper 30s in spots. Thereafter, additional shortwave
activity may continue to keep a trough carved out across the
northeast CONUS into early next week, promising continued below-
normal temperatures and further chances of wintry precipitation.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
KEY MESSAGES:

- Snow arrives after 06z bringing widespread IFR and lower
  restrictions areawide
- Period of worst conditions likely between 08z-14z
- Southeasterly wind veers northwesterly by Tuesday afternoon
-------------------------------------------------------------------

Widespread snow (and wintry mix in the Mon Valley) is ongoing to
start the TAF period, with a mix of IFR/LIFR ceilings and
visibilities at all area terminals. These conditions will
continue until accumulating snow ends from west to east during
mid and late morning. Latest guidance continues to suggest this
happens roughly in the 13z-14z timeframe at ZZV, 14z-15z at
PIT/AGC, and 16z-18z at LBE/DUJ. Flurries may linger across
western PA through the afternoon, but little to no accumulation
nor any notable impact to visibilities are expected. Ceilings
are expected to gradually rise to MVFR through the afternoon,
but may lower again (except for ZZV) this evening and overnight
tonight.

Light and variable winds this morning become northwesterly and
increase slightly (occasional gusts to around 15kts) by this
afternoon following a cold frontal passage.

Outlook...
Gradual ceiling improvement is expected on Wednesday with
eventual return to VFR Wednesday afternoon. Additional light
snow chances and restrictions are possible again Wednesday night
into Thursday morning (favoring locations north of PIT) and
during the day Friday (favoring locations south of PIT).

&&

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

&&

$$

SYNOPSIS...CL
NEAR TERM...CL
SHORT TERM...CL
LONG TERM...CL
AVIATION...Cermak