083
FXUS61 KPBZ 170053
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
853 PM EDT Thu Oct 16 2025

.SYNOPSIS...
Dry weather is expected for most of the area through Saturday as
high pressure moves east across the region, though a weak warm
front will bring a chance for very light rain west and north of
Pittsburgh Friday night. A strong cold front will bring
showers, possible thunderstorms, and gusty wind on Sunday.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
KEY MESSAGES:

- Dry weather continues under high pressure.
- Frost/freeze threat into early Friday morning

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

Evening Update:

In coordination with surrounding WFOs, lowered dewpoints
considerable using latest HRRR runs and 10th percentile NBM
data to better align with observed conditions. Also increased
wind/wind gusts on Sunday by blending in NBM90th guidance to
better align with analogs. No other changes were made. Previous
discussion follows..


PREVIOUS..

Similar conditions are expected tonight compared to last night,
but with higher confidence in calmer wind and colder overnight
lows. The probability for the vast majority of the area to see
frost is high at 80-100% (lowest in the urban areas and
immediately along the Ohio River). Continuing to see lower
probabilities for temperatures <32F in the HREF than I would
normally like, but with high pressure centered more directly
over the area I have higher confidence that winds will settle
more than it seems to suggest. Therefore, favoring NBM
probabilities for tonight`s freeze potential, which shows a
60-80% chance for counties north of Pittsburgh and along the
ridges of SW PA and northern WV. Taking this into consideration,
opted to upgrade to a Freeze Warning for those counties, while
a Frost Advisory was favored for the rest of the area.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
KEY MESSAGES:

- Well above normal temperatures for the weekend
- Scattered showers possible Friday night
- Cold front passage Sunday offers higher rain chances and windy
  conditions
----------------------------------------------------------------

We`ll finally get some mid-level height rises locally as the ridge
axis shifts eastward. Surface high pressure remains situated
overhead and plenty of subsidence will keep dry conditions in place,
though clouds will be on the increase from northwest to southeast
through the daytime hours as some increase in mid and upper level
moisture rides around the ridge. We`ll bring some warm
advection/weak shortwave driven rain shower chances in late Friday
into very early Saturday, but this shouldn`t amount to a whole
lot as lingering dry air in the sfc-700mb layer will result in a
fair amount of sub-cloud evaporation. The most likely areas to
see some accumulation (on the order of a few hundredths of an
inch) are north of I-80, while farther south most of the area
might just see some intermittent sprinkles resulting in little
or no accumulation.

Saturday will be a transition day of sorts as a more complex pattern
begins to take shape. A trough deepens over the central CONUS and
pushes the narrow upper ridge over the eastern seaboard eastward
over the Atlantic. A rather potent shortwave ejects eastward from
the central Rockies during the day Saturday, traversing the Plains
and reaching the Mississippi Valley overnight Saturday into early
Sunday morning. Meanwhile, a surface low develops in the IA/WI/IL
vicinity, which rapidly deepens and lifts northeast towards the
Great Lakes, eventually becoming vertically stacked beneath the
parent shortwave. As all of this occurs, it causes deep-layer
southwesterly flow to strengthen downstream over the Ohio Valley and
lower Great Lakes, which in turn brings moisture and unsettled
weather back to the local area Saturday night through Sunday night.
This will also result in a warming trend for temperatures Saturday
and Sunday, with highs climbing into the low 70s each day.

Sunday`s forecast becomes more interesting with a dynamic system
bringing a two-fold threat. First, the stacked low moves closer in
proximity to the local area as it crosses the Michigan lower
peninsula and southern Ontario, which will cause the pressure
gradient between it and a broad surface high centered off the
southeastern U.S. coast to tighten. In addition, ensembles suggest
the deep-layer flow to be quite strong as expected this time of year
with around a 50-60% chance for 925 mb wind to exceed 35 knots
which forecast soundings suggest will be easily mixed down to
the surface. This will result in an uptick in non-convective
winds. Latest probabilities for max wind gusts exceeding 30 mph
on Sunday are have increased notably across the entire area with
80-100%, while probabilities for max gusts exceeding 40 mph
have followed the same trend up to 40-70%. The second hazard
will be showers and thunderstorms associated with this system. A
cold front will pass through sometime on Sunday, though latest
ensemble clusters still show a very low confidence pattern with
the majority of uncertainty stemming from a timing issue with
the parent trough. There`s about an even split between those
members who suggest it`s quicker and through the area Sunday
afternoon while the others hold it back until later Sunday
evening. This evolution will impact frontal passage timing and
potential thunderstorm development. This will be a high
shear/low CAPE setup with mean NBM SBCAPE around 200-400 J/kg
and 90th percentile values (contingent on any low probability
scattering of clouds) sneaking up as high as 600 J/kg. Deep
layer shear will be strong (LREF mean sfc-500mb shear up to or
even in excess of 50 knots), so if any deep updrafts are able to
form, they will be in an environment that supports at least a
limited damaging wind threat, though such a high shear/low CAPE
environment lends question as to whether or not there could be
too much shear for the little CAPE in place. This will all be
ironed out more in the coming days.

&&

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

- Cooler weather returns next week
- Periodic rain chances for the first half of the week
-------------------------------------------------------------------

Notable upper level pattern discrepancy continues and increases into
next week with some ensembles holding the trough back and closing it
off into an upper low while others quickly progress it offshore as
an open wave. The slower, deeper solution could result in rain
chances remaining on Monday with low level cold advection and
periodic shortwave passage while a quicker one allows high pressure
and drier air to sneak in quicker. Think that we likely will keep
some showers around Monday morning with lingering low level moisture
and cold advection reinforcing steeper low level lapse rates, and
the latest NBM offers 20-30% PoPs which seems reasonable at
this juncture.

High pressure does eventually build behind the departing low, though
how long it stays around is uncertain as ensembles develop another
surface low off to our northwest with additional rain chances
returning as early as Tuesday. Given cascading differences among
solutions even for this coming weekend, confidence beyond that
timeframe is very low at this time.

&&

.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
High confidence in VFR through the TAF period under the
influence of high pressure crossing north of the region. Strong
radiational cooling with light wind favors river valley steam
fog Friday morning between 06z-12z, but confidence in terminal
impact is too low for mention (highest probs are at
FKL/HLG/AGC).

Warm advection aloft ahead of the ridge axis is expected to
increase mid to high level clouds after 18z Friday.

.OUTLOOK...
VFR is expected through Saturday with increasing mid/high clouds
and a very low probability for a non-impactful light rain shower
or sprinkle over NW PA during the morning.

A potent low pressure system will cross the region Sunday,
aiding in widespread precipitation and high probabilities for
periods of restrictions. Current model means suggest no more
than 15-30% probability of a thunderstorm, but a strong low
level jet and gradient winds will create significant increases
in synoptic wind and potential for shower enhancement on high-
end gust potential.

Occlusion of the low may maintain restrictions and area showers
late Sunday into Monday morning within the cooler post-frontal
environment. Dry advection and shortwave ridging likely creates
VFR by Monday evening, but an active weather pattern next week
favors periodic precipitation/restriction chances.

 &&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Frost Advisory from 2 AM to 9 AM EDT Friday for PAZ007-013-020-
     021-029-031.
     Freeze Warning from 2 AM to 9 AM EDT Friday for PAZ008-009-
     014>016-022-073>078.
OH...Frost Advisory from 2 AM to 9 AM EDT Friday for OHZ039>041-
     048>050-057>059-068-069.
WV...Frost Advisory from 2 AM to 9 AM EDT Friday for WVZ001>004-012-
     021-509-510.
     Freeze Warning from 2 AM to 9 AM EDT Friday for WVZ511>514.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Frost Advisory from 2 AM to 9 AM EDT Friday for PAZ007-013-020-
     021-029-031.
     Freeze Warning from 2 AM to 9 AM EDT Friday for PAZ008-009-
     014>016-022-073>078.
OH...Frost Advisory from 2 AM to 9 AM EDT Friday for OHZ039>041-
     048>050-057>059-068-069.
WV...Frost Advisory from 2 AM to 9 AM EDT Friday for WVZ001>004-012-
     021-509-510.
     Freeze Warning from 2 AM to 9 AM EDT Friday for WVZ511>514.

&&

$$

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