494
FXUS61 KPBZ 101859
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
159 PM EST Mon Nov 10 2025

.SYNOPSIS...
Snow showers continue through Monday night with minor impacts in
the lowlands. Lake effect snow bands expected along and north
of Interstate 80 with localized impactful accumulation, and
upslope flow in the PA and WV ridges will also result in
snowfall impacts. Snow will taper off on Tuesday outside of
Interstate 80 and the ridges, though another disturbance on
Wednesday will reintroduce rain and snow showers.

&&

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

- Snow continues across the area with generally an inch or less in
  the lowlands
- Highest amounts in the ridges with upslope flow and I-80 corridor
  with lake effect bands
- Mercer & Venango Counties upgraded to Lake Effect Snow Warning
- Tucker County upgraded to Winter Storm Warning
- Snow tapers off on Tuesday with gusty wind
---------------------------------------------------------------

A deep upper low parked across the Great Lakes region with northwest
flow in the wake of low pressure sliding through the Northeast has
turned on the lake effect snow machine and will bring impactful snow
to parts of the area through tonight.

Starting with the lowlands... scattered snow showers will continue
in northwest flow through the day today. These have taken on a
convective nature with meager SBCAPE and steep low level lapse rates
supporting cellular development. Latest aircraft soundings from PIT
suggest that the moisture hasn`t quite settled in to the DGZ early
this afternoon, and is thus limiting the ceiling for efficient
dendritic growth. Forecast CAM soundings do hint that a bit deeper
moisture may work in this afternoon and allow for more efficient
snow crystal growth, but still roadway temperatures are in the 40s
which will limit any accumulation on roads. That will change tonight
as air temperatures plummet into the 20s for overnight lows, roadway
temperatures dip below freezing, and snow showers remain.
Accumulation on all surfaces will become more likely, though
coverage still will remain scattered and not expecting more than
an inch or so; it`s more likely that the majority see less, but
it`ll likely look more white on Tuesday morning than it did
Monday morning.

For the I-80 corridor... this is where the most impactful snow is
expected with this event, though the highest accumulations will be
very localized. Lake effect snow showers are underway this afternoon
without a lot of organization yet as the 925-850 mb wind difference
still exhibits some directional discontinuity and is prohibiting
coherent band(s) from developing. Into tonight, flow should become
more aligned and gradually back in direction allowing for banding to
set up. What is likely to happen is that the disorganized showers
east of Cleveland this afternoon will form a more coherent band with
source fetch perhaps all the way up to Huron and pivot to the east
coincident with the well-aligned, backing flow tonight after 00z.
Colder air aloft will settle in and a favorable combination of
saturation through a deep DGZ, maximized lift within this favored
zone, and steep lapse rates will allow for a very efficient lake
effect snow band. Analysis of the 12z CAMs/HREF elicit high
confidence in the occurrence of a band but medium confidence in its
location. HREF footprint suggests the northern half of of Mercer and
Venango Counties are most likely to be impacted, but increasing the
neighborhood radius (accounting for spatial uncertainty) raises the
possibility that the band could extend as far south as far northern
Butler and Lawrence Counties and/or as far east as Forest County.
HREF snow accumulation assumes a 10:1 snow to liquid ratio which,
for this case, is too low, and more likely around 16-18:1. The 90th
percentile QPF, which is a reasonable representation of the highest
liquid equivalent within lake effect bands, is around 0.70". So,
this points toward some highly localized amounts within those
counties up to the 10-12" range. Probability of 1"/hour rates is
80+% with 2"/hour rates at 40-50%. Outside of the band, amounts
will be much less and in the 2-4" range. Because of this, the
Winter Weather Advisory has been upgraded to a Lake Effect Snow
Warning for Mercer and Venango Counties. The takeaway message
is that part of those counties is likely to see impactful
accumulating snow tonight with greatly reduced visibility and
hazardous travel conditions while lesser amounts are expected
elsewhere in the county.

For the ridges... upslope enhancement will aid in higher totals for
both our PA and WV ridges. As discussed, the boundary layer
flow will gradually back through tonight and thus not result in
persistent favorable direction for upslope along all of our
ridges. Initially, the heaviest snow and highest accumulation
should be in the WV ridges with a north-northwest flow
maximizing orographic ascent. As flow backs, it`ll become more
orthogonal to the PA ridges and transfer better rates and
accumulation there. With colder surface temperatures, it should
be easier to lay on all ground surfaces and create impactful
travel conditions tonight. Leaning on NBM 90th for snowfall
totals in Tucker County, which performs well as at least a base
amount, suggests at least warning criteria snow. HREF
probability for >6" in Tucker County is near 40% but, again,
this assumes a 10:1 SLR; reality is closer to 17-19:1 which
points closer to the 8-10" range and sufficient for an upgrade
to a Winter Storm Warning. Rates may exceed 1"/hour with a
60-80% probability. Elsewhere in the ridges, lesser total liquid
of up to ~0.3" leans toward advisory criteria snow in the 3-5"
range, so have maintained the remainder of the Winter Weather
Advisories as is.

Through the day tomorrow, flow will back more and eventually turn
west to west-southwest and taper off the lake enhancement for our
area. It`ll linger longest along and north of I-80, as well as in
the PA ridges, with a broader coverage of light snow showers
possible aided by increased synoptic ascent with a passing mid-level
wave. Some additional light accumulation is possible. Drier air
finally advects in from the west on the back side of the mid-level
trough as it moves east and will shut off the snow entirely by late
afternoon. The other story of the day will be gusty wind with a
tight pressure gradient and diurnal mixing into 25-35 knot low level
flow with momentum transfer resulting in surface gusts to 30 mph.
With high temperatures in the low to mid 30s, wind chill values will
hover in the 20s for most of the day. Eastern Tucker County likely
sees values into the negative single digits especially early Tuesday
morning.

&&

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

- Passing disturbance maintains lake effect snow showers north of
  I-80 and in the ridges on Wednesday
----------------------------------------------------------------

Upper troughing remains dominant on Wednesday with transient surface
ridging maintaining mostly dry conditions south of Pittsburgh. To
the north and in the ridges, additional lake effect and upslope snow
showers are likely with PVA and a weak surface trough passage. Flow
should remain mostly out of the west thus keeping the best lake
effect tucked closer to the lake itself. We`ll struggle to get a
good shot of cold air with surface flow out of the southwest and
highs reaching the low to mid 40s across the area, so surface
temperatures will be much more marginal with this event. NBM
probability for >1" is low in our area (<20%) which makes sense
given the environment, and any accumulation may be confined to
elevated surfaces. Wind will still be gusty but with moderating
temperatures won`t see a wind chill impact.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
- Dry weather with moderating temperatures Thursday and Friday
- Temperatures closer to normal heading into the weekend
-------------------------------------------------------------------

The long term begins with northwesterly flow and subtly rising
heights as the upper trough kicks eastward into Atlantic Canada and
an upper ridge noses into the area from the central CONUS. At the
SFC, high pressure settles in from the west and dry conditions are
expected. With subtle height rises, temperatures continue to trend
upwards through late week, approaching average by Friday. A slow
moving warm front looks to return rain chances by Friday night,
before more widespread rain chances are expected with the parent low
later this weekend.

Ensembles are in good agreement that the ridge gets kicked eastward
by a western trough on Saturday, residing almost overhead. However,
they quickly diverge on Sunday with their depth and location of said
western trough. A couple clusters feature height falls for our area
as an open wave presses eastward and breaks the ridge down shunting
it eastward. Another cluster slows the pattern down by developing a
cutoff low near the four corners allowing ridging to remain
overhead.

Either way, both scenarios hint at the ridge moving eastward and the
return of upper troughing to end the weekend or begin next week.
This would bring cooler temperatures and more unsettled weather, the
difference remains in just how fast we get there. For now the
forecast features above average temperatures lasting through Sunday
and then dropping to begin next week. Precipitation chances look to
remain elevated into early next week.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
Enough mixing has occurred this afternoon to allow ceilings to lift
to VFR levels across the area, with peeks of sunshine in between
ongoing lake-effect snow showers. These conditions will continue
through the rest of the afternoon, though an uptick in the intensity
of snow showers is expected as additional heating and mixing help
deepen and moisten the boundary layer. The bulk of snow shower
activity is also expected to rotate from eastern OH to western PA
and then northwestern PA through the rest of the afternoon and
evening as winds back from northwesterly to westerly. Expect sudden
reductions in visibilities and ceilings in any snow showers that
impact area terminals; most likely IFR but potentially LIFR in the
heaviest cells. Showers generally taper off south of I-80 tonight,
but linger over the ridges (thanks to upslope enhancement) and north
of I-80, the latter which may continue to see occasional heavy rates
(1-2 in/hr) through Tuesday morning.

Widespread MVFR ceilings return to areas outside of snow showers
overnight as cold NW flow continues off the lakes. Westerly winds
become breezy after sunrise Tuesday morning, with gusts as high as
25-30 knots at most terminals.

Outlook...
A gradual improvement to VFR is expected during the day
Tuesday along with breezy west-southwest winds. Restriction
potential returns Wednesday with rain and snow showers under another
crossing trough. VFR returns Thursday and Friday under high
pressure.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Lake Effect Snow Warning until 1 PM EST Tuesday for PAZ007-008.
     Winter Weather Advisory until 1 PM EST Tuesday for PAZ009-074-
     076.
OH...None.
WV...Winter Weather Advisory until 1 PM EST Tuesday for WVZ510>512.
     Winter Storm Warning until 1 PM EST Tuesday for WVZ513-514.

&&

$$

SYNOPSIS...MLB
NEAR TERM...MLB
SHORT TERM...MLB
LONG TERM...AK
AVIATION...Cermak