068
FXUS61 KPBZ 091820
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
120 PM EST Tue Dec 9 2025

.SYNOPSIS...
Active weather pattern through the weekend will bring rounds of
snow, occasionally mixed with rain, as well as fluctuating
temperature and gusty winds. Overall, snowfall accumulations
favor areas north of Interstate 80 and the ridges of southwest
Pennsylvania and northern West Virginia.

&&

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

- Weak, fast moving disturbance brings light snow to northwest PA
  this afternoon with light accumulation
- Another stronger system brings mix of rain and snow to the
  lowlands with accumulating snow in the ridges and I-80 corridor
  where various winter headlines have been issued
- Strong wind gusts on Wednesday
---------------------------------------------------------------

A weak shortwave will cross the Great Lakes region today and slide
by to our north across Lake Erie. As high pressure slides to the
Atlantic Coast in response to its approach, weak warm advection will
lift area temperatures to the mid 30s. Deep layer flow out of the
west is limiting column moisture return, especially south of
Pittsburgh. Expect that as this shortwave moves through this
afternoon, and convergence along the leading edge of an 850 mb jet,
light snow will overspread the area north of Pittsburgh, and mostly
along and north of I-80. Thermal profiles favor all snow with
sufficient moisture into the DGZ, deeper moisture/strong lift and
marginal surface temperatures right around or possibly even a degree
or two above freezing keeps accumulation probability low
(probability for measurable snow is 20% or less).

A brief dry period ensues tonight out ahead of a stronger trough
diving through the Great Lakes, and slightly deeper than the first
one. Surface cyclogenesis occurs rapidly with strengthening as it
pivots to the northeast just north of Lake Erie. A stalled front
from the Tuesday afternoon wave lifts northward as a warm front as
southwest flow develops ahead of the approaching low. Strengthening
right exit region mid-level jet aided ascent along with the warm
front will aid precipitation development into northwest PA and
eastern OH during overnight hours, progressing east into the
morning. With deeper moisture and better ascent aligning north of
the front, a second, heavier wave of snowfall is expected along and
north of the I-80 corridor generally after Midnight through
Wednesday early afternoon. A Winter Weather Advisory remains in
effect for Mercer, Venango, Forest, Clarion, and Jefferson Counties
starting at 1 AM EST through Thursday afternoon. Thermal profiles
suggest a wet snow with SLRs <10:1 but plenty of deep moisture and
localized ascent in the DGZ. The period of heaviest snow is likely
to fall in the 1AM - 7AM window along I-80 roughly from I-79 and
west, and then 7AM - 1PM along I-80 east of I-79. Probability for
Advisory criteria snow remains elevated with most of those counties
seeing 3-5 inches and locally up to 6 inches. This will impact the
morning commute.

In far southwest PA and northern WV, snowfall onset is expected
after sunrise. Here, there is potential for snowfall accumulations
to reach 3 to 5 inches, but most accumulation will be confined to
the high elevations as surface temperatures in the lowlands are
likely to remain too warm for significant accumulation. At onset, a
period of wet-bulbing may allow for a rain/snow mix or a quick burst
of wet snow ahead of a transition to mostly rain. That said, in the
higher ridges of eastern Tucker County and Preston County, snow is
likely the predominant precip type with little rain contamination.
NBM has come in with up to a 70% chance of >6" of snow, but
typically underdoes the snowfall totals in the ridges. The more
reliable HREF for elevation-driven accumulation suggests an 80%
chance of >6", and assumes a 10:1 ratio which may be slightly
underdone, even though strong wind tends to break up dendrites and
lower snow ratios. The additional caveat to this is said high
probability for a prolonged period of wind gusts to remain above
35 mph (and as high as 60 mph in the highest elevation)
coincident with snowfall and snow accumulation. This meets the
criteria for a blizzard, and thus the Winter Storm Warning has
been upgraded to a Blizzard Warning for Eastern Tucker County
and Eastern Preston County running from 10am Wed - 10am Thu.

Where the most tricky part of the forecast comes in is actually for
the lower elevations of eastern OH and southwestern PA. 12z CAMs
have taken on a slightly colder solution as the shield of precip
arrives before sunrise and an enhanced push in the mid-morning
hours. Forecast soundings show a very deep saturated layer well
through and above the DGZ with strong synoptic forcing. Most of the
entire profile is below freezing save the lowest few hundred feet
where surface temperatures sit a degree or two above freezing.
Should this be the case, a wet and cold rain will be the result.
However, if surface temps are slightly overdone by the CAMs and/or
dynamics cool the profile further than advertised, there is a
conditional threat for a thump of heavy, wet snow to impact a good
portion of southwest Pennsylvania, eastern Ohio, and the panhandle
of West Virginia in the early morning to early afternoon hours. This
may be a situation in which we have to see the whites of its eyes in
the morning before knowing how it exactly will play out, but the
worst case scenario could be a couple inches of accumulation
with impacts to the morning commute.

Finally, by the afternoon hours, a transition to convective snow
showers with continued upslope in the ridges is likely as the
stronger synoptic forcing moves east. Profiles suggest
sufficient saturation through the DGZ remaining with steepening
lapse rates in a low-level cold advection regime. Localized
snow bands could produce another burst of accumulation and
visibility reduction for the afternoon commute.

Beyond the precipitation, tight surface gradients will foster gusty
wind between 30-40 mph in the afternoon in the lower elevations,
with 40-50 mph gusts possible in the ridges and peak gusts as high
as 60 mph possible in the highest ridges of eastern Tucker County,
WV.

&&

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

- Transition to lingering upslope and lake enhanced snow
- Temperatures well below average
----------------------------------------------------------------

Rapid movement of the surface low and upper trough over the New
England region Wednesday night will bring colder temperatures under
northwest flow. Cold air over the still mostly open lakes is likely
to turn on the lake effect machine. CAMs in range are starting to
light up some Huron to Erie banding potentially impacting our I-80
counties, but confidence at this time in location and amounts is
low. The Winter Weather Advisories up there extend through Wednesday
night, and decisions may have to be made on potential extension
further if lake effect bands will continue to bring accumulation
well into Thursday. It will otherwise be cold with highs struggling
to top 30 degrees and a brisk westerly wind.

&&

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

- Quick disturbance brings light snow to WV Friday
- Another chance for snow Saturday into Sunday
- Temperatures remain well below average through the weekend
-------------------------------------------------------------------

The unsettled pattern continues to close out the week and into next
weekend as mid-level troughing continues to plague the ECONUS.
A weak shortwave embedded within the broader trough brings another
round of snow to the WV ridges while lake-effect snow showers
continue north of I-80. Eventually, the upper low over New England
advances eastward over the Atlantic as another upper low dives from
northern Canada towards the upper Great Lakes. This allows
additional shots of cold air to filter in, albeit with both timing
and depth differences evident among global models. Yet another
system is possible on Saturday into Sunday bringing more snow but
still with much uncertainty.

Confidence is increasing in a several day period where we have high
temperatures some 15-20 degrees below average in the cP airmass
through the weekend with highs in the 20s and lows in the teens or
single digits. Cold air being entrenched across the region means any
additional disturbances are likely to produce snow as the prevailing
precip type areawide. While the overall pattern appears messy and
ensembles are clearly struggling to agree on timing and intensity of
any given wave, confidence is increase in at least one more shot at
snowfall  over the weekend before long term guidance finally has the
eastern Canadian longwave trough breaking down. Stay tuned for more
details as we get closer and confidence increases.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
KEY MESSAGES:

- Restrictions in snow at FKL and DUJ possible overnight
- Increasing S-SW wind into the overnight period.
-------------------------------------------------------------------
 A crossing warm front will provide sufficient lift areas north
 of I-80, where FKL and DUJ could see restrictions in snow this
 evening and overnight. Gusty winds will persist with a tight
 pressure gradient and a well mixed boundary layer. Snow
 overnight will transition to a wintry mix early in the morning
 and eventually rain with IFR or lower cigs likely by late
 morning. Latest HREF guidance shows increasing IFR cigs over
 the morning, and eventually a 90-100% chance areawide by early
 afternoon.; This is also supported by latest analogs.

Outlook... Restrictions and scattered snow showers are expected
Thursday and Friday with a crossing upper trough, and again
Saturday with approaching low pressure.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Winter Weather Advisory from 1 AM to 10 PM EST Wednesday for
     PAZ007>009-015-016.
     Winter Weather Advisory from 10 AM Wednesday to 10 AM EST
     Thursday for PAZ074-076-078.
OH...None.
WV...Winter Weather Advisory from 10 AM Wednesday to 10 AM EST
     Thursday for WVZ511-513.
     Blizzard Warning from 10 AM Wednesday to 10 AM EST Thursday
     for WVZ512-514.

&&

$$

SYNOPSIS...Cermak
NEAR TERM...MLB
SHORT TERM...MLB
LONG TERM...Cermak/MLB
AVIATION...88