190
FXUS61 KPBZ 171137
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
737 AM EDT Thu Jul 17 2025

.SYNOPSIS...
Frontal passage will favor showers and thunderstorms south of
Pittsburgh through Friday while northern locales experience
drier and more seasonable weather. Widespread thunderstorm
chances return Saturday into next week as the active weather
pattern continues.

&&

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

- Frontal passage will support thunderstorms south of Pittsburgh
  and dry/seasonable weather north today
- Higher rainfall rates and increasingly saturated grounds
  creates risk for flash flooding
---------------------------------------------------------------

Brief subsidence between shortwave perturbations will allow for
much of the region to start the day dry with only low
probabilities for an isolated shower.

Weak shortwave movement within quasi-zonal flow aloft will aid
in the eastward movement of a surface low from central MI
towards southeastern Canada today. This will push a surface cold
front SE through the morning that may initially be dry given
weak forcing aloft and CIN in the region. As the boundary
approaches the I-70 corridor shortly after noon, ensemble models
favor an uptick in convective initiation that will lead to waves
of west to east moving thunderstorms through the evening. A
slightly less buoyant/moist environment than Wednesday (SBCAPE
values closer to 1500 J/kg and PWATs closer to 90th percentile)
will still be enough to foster a 1-2"/hr rainfall rates with
localized totals that could exceed 3". Based on increasingly
saturated grounds, high PWATs, and potential for some storm
training as the surface boundary becomes parallel to upper
flow, a Flood Watch for flash flooding was issued for most of
northern WV from 2pm-midnight tonight; this coincides with
WPC`s Slight Risk Excessive Rainfall Outlook.

Hi-res modeling continues to be bullish in dry weather north of
the boundary today, with slight cool/dry advection leading to
more seasonable afternoon temperatures.  The surface boundary
will stall near the I-68 corridor tonight as it becomes
displaced from the upper shortwave, with convective activity
generally dissipating by 06z with the loss of heating/jet
ascent. That said, isolated showers may continue into Friday
morning along the stalled boundary given the warm, moist
environment.

&&

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

- Diurnally driven convection is expected along and south of the
  stalled boundary, favoring mainly northern WV.
- Areas north of the front are likely to remain dry with
  seasonable temperature.

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

Quasi-zonal flow aloft with contain very weak perturbations that
will interact with the stalled surface boundary and diurnal
heating to develop scattered thunderstorms mainly over northern
WV Friday. High pressure to the north of the boundary will
support dry, seasonable weather as afternoon high temperature
falls near to slightly below the daily average. For the storm
environment, little air mass change from Thursday means high
PWATs (near 90th percentile) with weak CAPE (less than 1000
J/kg) and weak shear mean localized flash flooding remains
possible. Ensemble signals suggest potential for 1-2"/hr rates
may lay just south of the region, but flood risk will be
monitored given increasingly saturated grounds and generally
favorable training set up (stalled boundary parallel to upper
flow).

Loss of diurnal heating is likely to limit areal coverage of
storms near the I-68 corridor Friday night, but not eliminate
the chances. The approach of additional shortwave energy from
the Upper Mississippi River Valley may act to lift the surface
front (and associated precipitation chances) northward
overnight.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
KEY MESSAGES:

- Ensembles trending toward continuing the active weather
  pattern Saturday into next week.
- Flood and severe potential remain highly uncertain and is
  likely largely predicated on prior days outcomes.
-------------------------------------------------------------------

Ensemble models are becoming increasingly bullish on widespread
convection returning to the forecast area Saturday in response
to shortwave movement within developing NW flow traverses the
Great Lakes region. However, there remains a large spread in
wave timing and storm coverage that will be influenced by the
degree of northward lift of the stalled WV boundary as well as
potential SE advancement of some sort of MCS system out of the
western Great Lakes. What can be said is that the warm/moist
airmass featuring 90th percentile and higher PWATs are favored
to be positioned over portions of southeast OH towards Tucker
County (WV) that would suggest an increased risk for flash
flooding. Further NE movement of these PWATs in ensuing model
runs (a possible scenario) would increase that risk further into
western PA. Other hazards like damaging wind can`t be ruled out
either.

The active pattern is favored to continue Sunday into next week
with a series of shortwaves crossing within NW flow as ridging
attempts to build over the MS River Valley. Timing and
variability of conditions remains high but the messaging of
continued flooding and severe threats is likely to continue.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
Areas of MVFR to IFR stratus will continue to lift and partially
erode this morning with mixing. The CU rule and model soundings
indicate a scattered to broken cumulus layer will develop as
convective temperatures are reached.

A surface boundary will drift south across the Upper Ohio
Valley region today, and will be the focus for afternoon showers
and thunderstorms. Maintained a prob30 mention for thunder for
airports generally from ZZV to PIT to LBE, where timing of
convective development along the boundary is in question. MGW
has a higher chance of seeing thunder, so maintained a Tempo
with a subsequent prob30 to account for convection along and
ahead of the boundary. Expect low MVFR to IFR stratus to develop
again overnight with low level moisture in place.

Outlook...
After morning stratus, shower and thunderstorm chances are
expected mainly south of a ZZV-LBE on Friday as the surface
boundary drifts southward. The front will return north as a warm
front on Saturday, with more numerous showers and thunderstorms
across the area. Additional showers/storms are expected Sunday
as the front returns south as a cold front. There will also be a
potential for overnight/early morning fog and stratus through
Sunday night. Mainly dry weather is expected for Monday as high
pressure begins to build in.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...Flood Watch from 2 PM EDT this afternoon through this evening
     for WVZ012-021-509>514.

&&

$$

SYNOPSIS...Frazier
NEAR TERM...Frazier
SHORT TERM...Frazier
LONG TERM...Frazier
AVIATION...WM