901
FXUS61 KPBZ 272310
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
610 PM EST Thu Nov 27 2025

.SYNOPSIS...
Light snow showers and flurries will continue through Friday for
most of the area but chances for heavier snow and accumulations
in northwest PA increase tonight into Friday morning. Dry
weather and continuation of seasonably cool temperature is
favored Saturday before the next wintry mix system, featuring
snow changing over to rain, arrives Sunday.

&&

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

- Cold and gusty with scattered snow showers and flurries
- Lake enhanced snow bands developing north of I-80
---------------------------------------------------------------

.. 5pm Update ..

Flow has shifted northwest today around 8 hours before model
most mesoscale models suggested this would happen, this will
lengthen the period of northwest flow over the I-80 corridor.
Additionally, a quasi- stable band of snow has developed on the
south shores of Lake Erie, and has set its course on Trumbull
and Mercer Counties inland of the lake-shore. Given guidance
over the last 24 hours, most has been bi-modal. If we received
that wind shift earlier, CAMs (led by the HRRR) suggested
warning criteria in Mercer County. By a back-of-the-hand
approximation, HREF max QPF of 0.6" combined with snow ratios of
12:1 to 15:1 suggest that 6" to 8" is the most likely absolute
maximum one might expect out of the snow band. With the HRRR
showing 5" to 6" using 10:1 ratios, it seemed likely enough that
Mercer would reach warning criteria to warrant an upgrade. Area
reports have suggested a light accumulation thus far, although
road temperature have just dropped below freezing in Mercer
County as of 4pm, suggesting a ramp up of accumulations is
possible as the band remains WNW through much of the overnight
period.

Some thoughts to ponder for the overnight period: some mesoscale
models including the HRRR and HRW suggest additional snow band
development starting Friday morning through Friday along the
axis of Venango, Clarion, and Jefferson Counties. If this
actually materializes, additional advisory or even warning
expansions may be needed, but this will have to be a real time
update conditional on formation. Should this band materialize,
localized amounts of 6" to 12" seem possible, most likely for
Venango County, but the formation itself is not guaranteed,
with many other CAMs snowing no banded signal.

As for eastern Tucker, a much more typical upslope snow setup is
expected. Despite its far distance from the Great Lakes,
snowfall ratios and rates are expected to pick up overnight as
the unstable saturated layer finds its way into the DGZ. Combine
this with some hint of a Lake Michigan upstream moisture
enhancement tomorrow, conditions looked even more favorable for
snow and blowing snow. Most CAMs have accumulations generally in
the 3" to 6" range, highest for the Dolly Sods area, though
totals above advisory criteria may be observed in Davis/Thomas.
Winds gusts up to 50mph will likely result in blowing snow
through the period. Further, and advisory was issued for Tucker
through 7pm Friday.

.. Previous Discussion ..

Upper troughing over the eastern Great Lakes region will subtle
changes in its shape tonight into Friday that begins to shift it
east while slowly introducing more NW boundary layer flow
across the forecast region. Prior to this wind shift
development, strong cold advection plus diurnal mixing is
helping to squeeze out areas of flurries to light snow showers
this afternoon. Short lake fetch and some wind shear should also
limit occurrence of heavy snow along the northern fringes of
Mercer/Venango/Forest counties, keeping initial accumulations
through 7pm to less than 2" (favoring grassy/elevated surfaces)
and impacts low.

The introduction of more northwest flow with some mid-level
vorticity advection, especially after 7pm, is likely to increase
heavy snow shower with localized snow band potential through
Friday morning. Accumulations and impacts, which would be driven
by 0.5-1"/hr snowfall rates in a consistent snow band or brief
heavy snow that drops rapidly drops visibility, may be
initially seen along/north of the I-80 corridor (thru midnight).
Those risks may expand thereafter to just south of the I-80
corridor as well as the higher terrain E/S of Pittsburgh (~
midnight through 10am). However, current trends plus available
modeling leaves uncertainty in the duration of a heavy snow band
over a single duration and the exact positioning of that band
due to the effects of wind shear and lesser lake fetches. Thus,
messaging remains the same highlighting approximately Advisory
level accumulations (~3-5") in Mercer/Venango/Forest Counties
but potential for a localized maxima that exceeds warning
amounts (6-8") if banding is persistent. Additionally, there is
potential (~40% probability) for more than 2" in eastern Tucker
aided by some upslope flow, but limited areal coverage and
uncertainty in consistency of snow showers precluded inclusion
of this area in a Winter Weather Advisory at this time.

The rest of the region through this period will continue to see
the occasional light snow shower with gusty winds on the order
of 20 to 35 mph (slightly higher in elevated areas) into Friday
morning. Height rises as the upper trough begins shifting more
east with building surface high pressure will work to erode snow
shower coverage (and intensity) through Friday afternoon,
resulting in diminished impacts by Friday night.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
KEY MESSAGES:

- Cold temperatures continue
- Dry by Saturday morning
- Snow returns Saturday night

----------------------------------------------------------------

Dry conditions resume Friday night as surface high pressure
builds back in and h500 heights rise 16-18dm by Saturday. Dry
conditions will be relatively short-lived though with the ridge
axis east of the region, an upper trough digs across the Central
CONUS, and the associated sfc low approaches the Upper Ohio
Valley region later in the day.

The deepening sfc low is forecast to move out of the midwest
and be over the northern Great Lakes by Sunday, and the increasing
moisture and ascent in warm advection, should result in snow
overspreading the region later Saturday night. Probabilities for
an inch or two of snow are highest north and west of PGH as
those areas should see enhanced lift under the left exit region
of the upper jet.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
KEY MESSAGES:

- Snow and rain for Sunday
- Generally dry Monday before unsettled weather returns by mid
  week
-------------------------------------------------------------------

The trough is progged to transition across the Upper Ohio
Valley region on Sunday, as the associated sfc low pulls a cold
front across the area. Snow should mix with and change to rain
in warm advection ahead of the front, though there is still
uncertainty in how strong the warm advection will be, and how
far north this changeover would occur. The precipitation should
end from W-E Sunday night after FROPA, though some snow could
linger north of PIT as the flow turns NW off of the lakes. High
pressure is expected to build in Monday, bringing a return to
dry weather.

The active pattern continues next week as a shortwave trough
transitions to the northeast east from the Central CONUS Monday
night into Tuesday, and a surface low develops near the Gulf
Coast. This trough is expected to cross the region on Tuesday,
as the surface low tracks along the coast. Rain and snow chances
return Monday night and Tuesday. Operational models differ on
the amount of warm advection ahead of the trough, while
ensembles indicate a colder solution with more snow as a precip
type. Will maintain a mention of rain and snow in the forecast
with the uncertainty at this time. Temperatures will generally
remain below average through the period.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
Current observations are on track with the prior forecast. There
is currently a split between MVFR (northern ports) and VFR cigs
(southern ports) across area sites. Cigs are generally expected
to lower to MVFR for all sites overnight (>50% chance) save
slightly lower chances at ZZV and MGW. There is generally a 30%
to 50% chance of IFR for most ports by tomorrow morning, save
MGW and ZZV.

The main restrictions will continue to be vis through the
period in snow showers. Continued instability and upper
troughing over the warm great lakes will most certainly
continue to provide the chance of flurries through the period
(VFR/MVFR vis) with embedded heavier snow showers (higher chance
of IFR vis in DUJ/FKL). Chances will continue overnight and
into the afternoon tomorrow with diurnal heating aiding in
mixing and instability.

Snow showers and cigs are generally expected to scatter for most
into tomorrow night, with a >50% chance that FKL and DUJ hang
onto broken MVFR decks with perhaps some light continuing snow.

Winds are expected to remain fairly uniform through the period,
generally westerly at the surface with occasional gusts into the
20kt to 30kt range.

Outlook...
A brief period of VFR is expected to return for Saturday with a
quick passing bout of high pressure. The next low pressure
system arrives early Sunday morning, creating widespread
precipitation chances with high confidence on MVFR to IFR
restrictions through the day. Thermal profiles suggest initial
precipitation may fall as snow and have some potential for
accumulation (favoring ZZV/BVI/FKL/DUJ) before warm advection
aides in a changeover to rain.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Lake Effect Snow Warning until 7 PM EST Friday for PAZ007.
     Winter Weather Advisory until 7 PM EST Friday for PAZ008-009.
OH...None.
WV...Winter Weather Advisory until 7 PM EST Friday for WVZ514.

&&

$$

SYNOPSIS...Frazier
NEAR TERM...Frazier/Milcarek
SHORT TERM...88/Milcarek
LONG TERM...WM/88
AVIATION...Milcarek