371
FXUS61 KPBZ 171830
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
230 PM EDT Thu Jul 17 2025

.SYNOPSIS...
A crossing front favors 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 wavering boundary
supports the continuation of an active weather pattern.

&&

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

- A crossing front bring showers and thunderstorms south of
  Pittsburgh through this evening, while locations to the north
  remain dry.
- Higher rainfall rates and increasingly saturated grounds
  creates risk for flash flooding, mainly south of I-70.
---------------------------------------------------------------

A surface front cuts across eastern Ohio/southwest Pennsylvania
this afternoon, extending from low pressure over the St.
Lawrence River Valley and spurred on by an associated shortwave
trough. Deep mixing over the region has allowed for 20 to 30
MPH wind gusts at the surface as a low-level jet crosses; these
gusts will subside this evening. Temperatures have reached
seasonable levels in the lower to mid 80s.

To the north of the boundary, dry conditions continue to be
favored, with seasonable temperature and lower dewpoints.
Convective development ahead of the front remained isolated
through 18Z, much of it confined to areas south of the PA/WV
border, although some cells are now forming in the Laurels.
This is in agreement with CAMs, which overall are fairly muted
regarding afternoon/evening activity. A decent environment
supporting efficient rainfall still exists south of the
boundary, particularly in the ongoing Flood Watch area.
Precipitable water values of 1.6 to 1.8 inches are in place
south of I-70, along with MLCAPE of 1000-2000 J/kg and warm
cloud depths of 10-12 thousand feet. Still cannot rule out the
potential of waves of east-to-west moving storms containing 1-2"
per hour rainfall rates. A training setup would be supported by
the boundary eventually becoming parallel to the zonal mid-
level flow as it moves south of Pittsburgh. Given the antecedent
saturated ground, maintenance of the ongoing watch seems
prudent, with any extension of said watch being deferred until
overnight trends become more clear. A secondary threat will be
the potential for isolated strong to damaging wind gusts over
the same general area, with pockets of 600-900 J/kg of downdraft
CAPE through the afternoon.

The surface boundary is still expected to stall near the I-68
corridor tonight. Convection will largely dissipate by 06Z with
the loss of heating and upper support. That said, isolated
showers may continue into Friday morning along the stalled
boundary given the warm, moist environment.

&&

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

- Diurnally driven convection is expected Friday along and south
  of the stalled boundary, favoring mainly northern WV, with dry
  conditions to the north.
- The front likely returns north on Saturday, bringing a risk
  of heavy rain and flooding to a wider area.

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

The front is likely to remain stuck to the south of Pittsburgh on
Friday, with weak mid-level ripples traversing from west to east to
the south of the boundary. This keeps rain/thunderstorm chances to
the south of Pittsburgh, mainly over northern West Virginia. To the
north, surface high pressure will favor dry weather and temperatures
even falling a touch below seasonable levels. Any risk of
flooding/severe wind gusts will remain confined to areas south
of the Mason-Dixon Line, where precipitable water values remain
above the 90th percentile and where there is a 40 percent chance
or greater chance of 1000 J/kg of surface-based CAPE. Deep shear
remains near or below 20 knots in this area as well, meaning
lower end downburst/storm training risks.

A slightly more potent shortwave traveling across the Middle
Ohio Valley on Saturday could waver the boundary back north
again, bringing the 90th percentile precipitable water air mass
back northward. There remains a bit of question as to the
northern extent of the boundary and deeper moisture, as well as
the possible influence of some sort of remnant MCS, crossing the
western Great Lakes during the morning. However, the moisture
level and the better potential for general support of lift leads
to high rain chances areawide. There remains decent confidence
that flash flooding risks will extend further north and east as
compared to Saturday, encompassing more of eastern Ohio,
northern West Virginia, and perhaps extreme southwest
Pennsylvania at least, with the potential for a larger area.
Further refinement in the threat area is likely once CAMs
encompass the Saturday period. For its part, WPC encircles the
entire CWA with a slight risk of excessive rainfall. Another
Flash Flood Watch for this period is certainly possible,
covering the afternoon and evening hours. Isolated instances of
damaging wind may be possible as well with possible dry air
aloft, supported by machine- learning guidance.

More scattered activity could linger into Saturday night
although intensity is likely to decrease with the diurnal loss
of instability. Another soupy night is forecast, with lows of 70
or higher south of I-80.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
KEY MESSAGES:

- Monday may feature a break from the rainfall and humidity as
  high pressure crosses.
- Occasional rain chances exist from Tuesday through Thursday as
  the overall weather pattern remains active.
- Flood and severe potential remain highly uncertain and is
  likely largely predicated on prior days outcomes.
-------------------------------------------------------------------

Ensembles are in decent agreement that the boundary will once again
sink south across the region on Sunday in response to increasing
northwest flow aloft on the periphery of building lower Mississippi
Valley ridging. Another round of showers and storms is likely, with
coverage peaking diurnally. With precipitable water remaining high,
a threat of at least isolated flash flooding issues remains, perhaps
with a tilt towards areas south of Pittsburgh depending on the
position of the front during the peak heating period. A severe risk
cannot be ruled out as well, with potential dry air aloft feeding a
downburst threat.

The best chance for a break in the rainfall (as well as the
humidity) appears to be Monday, as surface high pressure traverses
the Great Lakes, keeping the boundary to the south. Thereafter, the
ridging expands northward into the lower/middle Ohio Valley, leading
to a slow build in 500mb heights over our region. Thus, a warming
trend back to above-normal temperatures expected -
probabilities for 90 degrees or higher rise into the 50 to 80
percent range by Thursday. Shortwave movement in the ongoing
northwest flow aloft will continue to provide shower and storm
chances from Tuesday on, and flooding/severe risks cannot be
ruled out during the period.

&&

.AVIATION /17Z THURSDAY THROUGH MONDAY/...
Scattered to broken cumulus clouds will continue through late
afternoon as convective temperature have been reached.

A surface boundary will drift south across the Upper Ohio
Valley region this afternoon and evening, and will be the focus
for showers and thunderstorms. Maintained a prob30 mention for
thunder for airports generally from ZZV 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 MVFR to IFR stratus and patchy fog
to develop overnight with low level moisture in place.

Outlook...
After any morning for or 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. A chance of
showers/storms returns Tuesday with approaching low pressure.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...Flood Watch until midnight EDT tonight for WVZ012-021-509>514.

&&

$$

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