832
FXUS61 KPBZ 121148
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
748 AM EDT Sat Jul 12 2025

.SYNOPSIS...
Seasonally warm temperatures with isolated shower storm coverage
are expected Saturday, before storm chances increase Sunday
with severe weather and flash flooding risks. A relatively drier
period is forecast next week with cumulative heat concerns.

&&

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

- Hot; high temperatures climb into the 90s and heat indices
  approach 100 degrees in spots.
- Isolated thunderstorms possible this evening into tonight,
  especially across east-central OH.
- Storms will be capable of producing damaging wind gusts and
  localized flooding issues in heavy downpours.
---------------------------------------------------------------

The environment will be similar today with perhaps a bit more
ridging in the flow pattern and stronger subsidence leading to
drier mid-levels. This will have two consequences: 1) dry air
entrainment will inhibit convective initiation keeping shower
and thunderstorm activity even more isolated than recent days,
and 2) the conditional probability of severe winds increases
(in other words, IF a storm with a strong updraft does form, the
chances that that storm produces damaging winds will be higher
than recent days). This is all supported by the latest ensembles
as well which show high confidence in at least 1000 J/kg MLCAPE
and near 1000 J/kg DCAPE. This would typically support a rather
serious damaging downburst wind threat, but with the abundance
of mid-level dry air there is low confidence in storms being
able to form and capitalize on that environment.

The highest chances of realizing the threat are in east-central
Ohio, where there is a low to medium probability of a pre-
frontal trough passage triggering isolated to widely-scattered
thunderstorm activity during late evening into early overnight
hours. The Storm Prediction Center has introduced a Marginal
Risk (level 1 out of 5) for damaging wind gusts should those
storms initiate. With PWATS again near the 75th to 90th
percentile, warm rain processes, and up-shear vectors of >5kts,
a localized flood threat also could not be ruled out.

One other consequence may be more breaks in the clouds, leading
to more sunshine which will help temperatures climb into the
90s across much of the area and could help head indices get near
or reach 100 degrees, especially in river valleys and urban
metros. Little relief is expected overnight with NBM showing a
greater than 50% chance of lows above 70F in eastern OH, the
lowlands of northern WV, and far southwest PA.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
KEY MESSAGES:

- Slightly higher severe wind threats and flash flooding threats
Sunday.
- Lingering shower/storm chances Monday.
- Monday temperatures in the mid to upper 80s.
----------------------------------------------------------------

More organized severe and flooding threats materialize Sunday with
the approach and passage of a front. This might make the chance of
storms themselves higher, but the conditional probability of a storm
being severe slightly lower. This forcing will be a mode for
initiation in an environment that is preconditioned with 1000 J/kg -
1500 J/kg MLCAPE and ensemble mean 600 J/kg - 800 J/kg DCAPE. This
is marginally enough to allow for a potential downburst wind threat.
SPC has issued a day two marginal risk.

As for flooding, the moisture push will likely take PWATS back
towards or higher than the 90th percentile with low-/mid-level flow
remaining around 10-15kts. With a deep warm layer and
proportionately higher coverage of precipitation, it seems at this
time that flooding may be the main threat to focus on as this wave
passes, though we will continue to analyze and message forecast
chances.

On Monday, a mid-level shortwave is still forecast to move through
the area. The timing has been uncertain with some ensemble members
pushing the axis through during the morning, and others lagging it
into the afternoon. Currently, it looks as if models are beginning
to agree on passing through during the afternoon. The highest
probability for precipitation is along the northern WV ridges. Some
timing adjustments are possible depending on whether the more
progressive solutions become more likely. Severe/flooding risks may
remain on an isolated basis with any storms, although areal coverage
of the threat should be lower as compared to Sunday. Temperatures
remain above normal with a very modest air mass change behind the
Sunday front.

&&

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

- Lingering shower/storm chances Monday
- Potentially drier Tuesday/Wednesday ahead of another low
  pressure system passage by late week
- Temperatures remain above average, with a peak in
  heat/humidity possible on Wednesday
-------------------------------------------------------------------

A drier pattern still appears likely Tuesday and Wednesday under
surface high pressure. The approach of a mid-level shortwave on
Wednesday, will likely provide the instability to produce diurnal
showers/storms on an isolated basis. The mid-level trough is
expected to remain relatively stationary through Friday.

Increasing southwest flow will help to bring the heat and humidity
back up for Tuesday and Wednesday as 850mb temperatures run back up
to 19C to 20C. Probabilities of 90F or greater max temperatures
increase to 55%-75% on Tuesday and 70%-90% on Wednesday with the
highest probabilities in the urban and valley areas while the ridges
will likely remain below 90F. NWS experimental Heat Risk values
again reach the "major" range by Wednesday.

The next chance of more widespread rain may arrive by Thursday, with
northern Great Lakes/eastern Canada low pressure dragging a frontal
boundary to and across the Upper Ohio Valley possibly by Friday.
Strength and timing issues remain in the ensembles, although overall
precipitation chances are heightened compared to earlier in the
week. Temperatures remain above normal, but the increased cloud and
rain coverage may reduce heat index values as compared to
Wednesday.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
Patchy valley fog is largely avoiding terminals this morning,
although DUJ and AGC are reporting MVFR mist that will largely
dissipate by 13Z. The remainder of the day will feature
scattered to broken VFR cumulus and S/SW wind of 10 knots or
less in most cases. Afternoon popup convection still appears too
isolated for TAF mention at this time, although impacts to any
one terminal cannot be totally ruled out.

Convection associated with a prefrontal trough will likely
impact western/central Ohio during the late afternoon/early
evening. A weakening trend is expected by the time such activity
would reach ZZV, but confidence in at least modest impact is
high enough here for a TEMPO mention after 21Z. Continued
weakening reduces confidence in occurrence further east, but
still used PROB30 for HLG/PIT/BVI/AGC. Confidence was too low to
add mention for FKL/DUJ/MGW/LBE. Have VFR conditions overnight
for now, but fog impacts are possible if/where convection occurs
earlier.

Outlook...
Isolated showers/storms may pass over the region into Sunday
morning in conjunction with an upper wave and presence of the
warm, moist airmass (but probabilities are still less than
20-30% on this occurrence).

Approach of a surface cold front and residual upper level
shortwave movement is likely to foster more widespread
convection Sunday that favors western PA and the higher terrain.
Ensemble models favor high pressure that drastically limits
convective potential Monday/Tuesday (but localized morning fog
can`t be ruled out).

&&

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

&&

$$

SYNOPSIS...Milcarek
NEAR TERM...Cermak/Milcarek/Shallenberger
SHORT TERM...Milcarek/Lupo
LONG TERM...CL/Lupo
AVIATION...Cermak/CL