259
FXUS61 KPBZ 031143
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
743 AM EDT Wed Sep 3 2025

.SYNOPSIS...
Showers and thunderstorms return Thursday with the approach and
passage of a cold front. Gusty winds and isolated severe storms
may be possible. Cooler conditions are expected over the
weekend.

&&

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

- Pre-frontal showers possible this evening mainly south of
  Pittsburgh
- Temperatures trend warmer than recent days/nights
---------------------------------------------------------------

An upper low dives southeastward over the northern Great Lakes
today, eventually stalling over southern Ontario. Low pressure
at the surface remains vertically stacked beneath the upper low,
with a surface trough and cold front rotating through its
southwestern quadrant and into the lower MI-IN-IL corridor by
this evening. Downstream from this, deep-layer southwesterly
flow sets up across the Ohio Valley and into western PA,
allowing moisture to gradually return to the region. Given how
dry deep-layer moisture profiles have been over recent days in
our area, it`s unlikely that enough moisture return occurs to
support any pre-frontal shower activity, leading to a dry near-
term forecast for most of the area (albeit under increasing
clouds). However, hi-res guidance does suggest some isolated to
scattered shower activity could developing along the nose of
the moisture plume this evening (approximately in the 5pm-10pm
timeframe) across northern WV and extreme southwest PA,
generally south of Pittsburgh. Low-end rain chances (around
20-30%) have been introduced in these areas in the latest
forecast to reflect this potential. Elsewhere, rain chances
don`t begin to increase until early Thursday morning ahead of
the encroaching cold front.

Temperatures see a warming trend today as highs climb into the
low to mid 80s. Overnight tonight into Thursday morning, temps
likewise trend milder than recent nights due to increasing
moisture under southwest flow, with lows remaining in the upper
50s to low 60s.

&&

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

- Showers and localized thunderstorms favored Thursday, likely
  in a morning and afternoon wave
- Marginal Risk for damaging wind dependent on heating ahead of
  afternoon wave
----------------------------------------------------------------

A fairly stacked low pressure system north of Lake Superior will
stall Thursday but still swing an initial lobe of energy
through the Ohio River Valley. The combination of strong upper
forcing and the approach of a surface cold front is expected to
generate showers and thunderstorms; initial Hi-Res convective
models favor this occurring in potentially two waves. The first
wave, consisting mainly of light to locally moderate rain
showers, will traverse west to east Thursday morning along a
pre-frontal surface trough and a notable 850-700mb jet. Delayed
arrival a mid-level cooling and expansion of cloud cover
eastward should limit buoyancy in the region and keep
lightning/severe activity low. Then, a secondary 850mb wave will
combine with the 500mb trough axis crossing to push the surface
front SE during the afternoon to early evening. Models are
confident in a strongly sheared (~40kts) environment with
straight line hodographs that portends to a damaging wind (and
non-zero tornadic) threat. However, variance remains very high
on the degree of heating/destabilization that can occur between
the two rounds, something that is key so that storm updrafts are
strong enough to not be sheared off. Hi-res modeling suggests
that locations SE of Pittsburgh are most likely to see enough
destabilization prior to frontal passage for this hazard threat
to materialize.

As the additional energy reorients the upper closed low Thursday
night into Friday, dry west to southwest flow is favored in the
wake of the passing front that will erode precipitation chances
by Friday morning. Shortwave movement N of the region may foster
a low probability shower Friday afternoon, otherwise models
favor dry and briefly seasonable weather amid warmer southwest
flow.

&&

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

- Additional shortwave movement will increase precipitation
  chances late Friday into Saturday
- Dry but seasonably cool weather is expected Sunday into the
  start of next week.
-------------------------------------------------------------------

Further pivoting of upper level energy around the northern Lake
Superior trough is likely to lead to another disturbance to
cross the Ohio River Valley late Friday into Saturday.
Variations remain in the timing/depth/positioning of the trough
axis, but ensembles favor broad jet ascent along and behind a
reinforcing cold front that results in additional shower and
isolated thunderstorm (non-severe) chances. Though current
ensemble means suggests rain accumulations will be around/less
than 0.5", large 24-hour rainfall spreads show potential for
localized frontogenetic processes that could enhance
accumulations to then exceed 1". Dry antecedent conditions and
scenarios where a deeper trough aligns the upper dry slot over
the area help to mitigate any flooding concerns.

High confidence exists in dry weather (save for low probability
of lake enhanced showers near the I-80 corridor) Sunday into
Monday as the upper trough axis moves east and high pressure
with rising heights filter in. Depending on cloud coverage,
Sunday may see afternoon temperature that is 10 to 15 degrees
below the daily average. Height rises will see warming
temperature through Tuesday as dry weather continues.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
VFR continues through the TAF period outside of a few patchy
instances of early morning river valley fog. Expect increasing
mid and upper level cloud cover as low pressure deepens over the
upper Great Lakes to our northwest. Southwest winds will be on
the increase this afternoon with some gusts up to 15 knots
possible. Can`t rule out a few showers over northern WV (MGW) and
extreme southwest PA (south of PIT/AGC), though no impactful
restrictions are anticipated, and confidence wasn`t high enough
for any mention in TAFs at this time.

After sunset tonight, wind gusts will cease and give way to light
south/southwest flow overnight. Thickening cloud coverage will
work in and lower, though still remain VFR, from the west ahead
of an approaching cold front.

.OUTLOOK....
An upper level trough and surface cold front are highly likely
to produce widespread rain with low-probability thunderstorms
early Thursday morning with then another round in the
afternoon and evening. Depending on the extent of clearing
after the morning batch, some of the storms with the second
round could bring gusty wind. Ensemble probability suggests a
50-70% chance for MVFR conditions associated with the rain
Thursday, with conditions potentially improving west to east
shortly after frontal passage. Non-convective wind is likely to
increase as well with gusts as high as 20-25 knots Thursday and
Friday afternoons.

Additional shortwave movement may offer additional rain and
restrictions chances late Friday into Saturday before dry weather
develops to start the next week.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.

&&

$$

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