526
FXUS61 KPBZ 151047
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
647 AM EDT Tue Jul 15 2025

.SYNOPSIS...
A warm, humid environment will favor daily rounds of showers
and thunderstorms Wednesday through Friday, which will increase
the risk for localized flooding for much of the region.
Temperature will settle closer to average by Friday, but heat
concerns will remain until then.

&&

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

- Erosion of morning fog expected.
- Low probability afternoon thunderstorms today that favor the
  higher terrain.
---------------------------------------------------------------

The influence of high pressure (light wind and clear sky) has
added in areas of fog that is locally dense this morning. Fog-
driven impacts will dissipate shortly after sunrise as
heating/mixing commences and a transition to broken and
scattered diurnal cumulus occurs. Most locations will see
temperature rise into the upper 80s to near 90 with heat indices
approaching 100. The probability is too low for a heat headline,
but precautions are encouraged to mitigate heat risks if you are
engaging in outdoor activities.

High pressure to the north and weak shortwave ridging overhead
will act as diurnal convective deterrents as slightly drier air
attempts to work in from the north. However, column moisture
will remain plentiful (PWATs near the 75th percentile) along
the higher terrain and areas south of Pittsburgh that any sort
of lift could result in isolated showers/thunderstorms. Latest
hi-res modeling suggests that convergence/lift and heating
combo is most likely to occur along the higher terrain in
Preston/Tucker Counties (WV). Convective initiation is favored
between Noon and 2pm and will have the potential for NW moving
outflows to spawn isolated storms into portions of southwest PA
and the northern WV panhandle. Due to the development of nearly
2000 J/kg SBCAPE and 1100 J/kg DCAPE, an isolated instance of
damaging downburst wind can`t be ruled out. And with storm
motion likely to be less than 15kts, localized flooding can
occur if storms persist too long over a given spot.

Loss of diurnal heating will aide in shower/thunderstorm
dissipation tonight. Fog that could be locally dense due to the
saturated boundary layer remains possible, but increased mid to
high level cloud cover from lower Ohio River Valley convection
may mitigate widespread development.

&&

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

- Widespread showers and thunderstorms are likely each day,
  favoring the afternoon and evening hours.
- Repeated rounds of heavy rain poses the risk of inducing flash
  flooding
- Outside of storms, rising dewpoints will increase heat risk
  throughout the region.

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

A nominal shortwave lifting northeast through the lower Ohio
River Valley Tuesday afternoon is likely to reach the forecast
area by Wednesday morning. This movement will aid in pushing a
surface boundary northward (increasing lift) and adding an
influx of surface moisture (increasing dew points) to the
already warm, moist environment for greater storm coverage that
can occur throughout the daylight hours. The convective
environment will be characterized by: near daily record PWAT
values; 1500-2000 J/kg SBCAPE; 15kts 0-6km shear; and weak mid-
level lapse rates. These values are indicative of a potential
flash flood environment depending upon whether storms can train
over a given location (500mb flow somewhat parallel to surface
boundary over eastern OH) or sit over a location long enough
(increased storm motion limits potential but could be overcome
by meso-scale convergence zones). Ensemble modeling suggests
that areas that could see a quick 1-2" (with locally higher
amounts) stretches from eastern OH through northwest PA;
confidence in flooding remains too low for Watch issuance at
this time.

Though the shortwave will exit east Wednesday night, the
environment will remain warm and humid which may allow for areas
of showers and thunderstorms to linger after sunset. Models
suggest that another shortwave passage will occur Thursday that
will push a weak cold frontal boundary ESE that again fosters
widespread convection. Variations do exist in the timing of the
shortwave/front combo that could result in a more muted storm
outcome compared to the current forecast. But the consensus
suggests another day with 90th percentile PWATS, moderate SBCAPE
and weak shear that would be conducive to flash flooding. Flood
Watch decision making for Thursday will likely be influenced by
Wednesday`s precipitation output and better consensus on
shortwave/front position in future model runs. Convection will
slowly wane Thursday night as the front sags and eventually
stalls somewhere south of Pittsburgh.

If a location does not experience a thunderstorm during the
early portion of the afternoons either Wednesday or Thursday, it
will stand to experience increased heat risk as high dew points
and near 90 temperature could cause heat indices to approach 100
degrees. No headlines are expected as storms are likely to cool
the environment and limit the duration of these conditions.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
KEY MESSAGES:

- More seasonable conditions are likely Friday with
  precipitation chances mainly south of I-70
- Any reprieve from storm potential is short-lived as active
  weather pattern likely resumes late Saturday into next week.
-------------------------------------------------------------------

The stalled surface cold front is likely to be positioned south
of Pittsburgh Friday. For areas north of the boundary, modest
dry, cool advection and high pressure will support dry weather
and temperature only a few degrees above the daily average. For
areas near to south of the boundary, residual moisture and jet
aided ascent is likely to foster scattered afternoon
thunderstorms; lowering PWATs and weak shear should limit flood
potential but keep the threat non-zero.

Ensemble models favor a transient area of high pressure north of
the area to slide toward New England Saturday but provide enough
influence to promote mostly dry weather (though the linger
stalled boundary south of the area could spawn isolated
afternoon storms). The pattern will begin to transition to move
northwesterly flow aloft late Saturday into early next week in
response to a ridge developing over the southern Great Plains.
This pattern alteration will continue the messaging of periodic
thunderstorm chances but these waves will be more tethered to
500mb and/or 700mb perturbations and be a bit lighter on the
precipitation side (more 75th percentile PWATS).

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
IFR to LIFR fog was observed across portions of the area, with
the most widespread coverage east and south of a line from UCP-
PIT-PHD. This fog should quickly dissipate this morning as
mixing begins. Otherwise, the CU rule and model soundings
indicate a scattered (to locally broken) diurnal cumulus layer
should develop as convective temperatures are reached. Capping
warmth aloft should limit any chance for thunderstorms, though
areas near LBE and MGW should see a slightly weaker cap, where
an afternoon thunderstorm is possible.

Expect VFR tonight with increasing high clouds ahead of an
approaching shortwave and surface warm front.

Outlook...
More numerous showers and thunderstorms are expected Wednesday
as a warm front lifts back north across the region. Daily
shower and thunderstorm chances are then expected to continue,
especially in the afternoons/evenings, as the front becomes
quasi-stationary and drifts across the region. Fog and stratus
is also possible each morning, especially where rain fell the
previous day.

&&

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

&&

$$

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