146
FXUS61 KPBZ 111646
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
1246 PM EDT Fri Jul 11 2025

.SYNOPSIS...
Seasonally warm temperatures with isolated shower storm coverage
are expected Friday and 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:

- Isolated afternoon/evening showers/storms with a low
  probability of flooding and severe weather.
- Heat risk up to moderate levels today.
- Warm overnight with additional valley fog chances.
---------------------------------------------------------------

Save a quick bout of morning convection riding the I-70
corridor, and the ridges in orographic lift, most of the region
will experience mostly clear skies with mixing allowing for
some fair weather cumulus. As the 12Z sounding and storms have
already shown this morning, instability in low level moisture
will continue to allow for afternoon/evening shower/storm
chances. Meso-analysis tends to suggest up to 1000 to 2000 J/kg
MLCAPE into this afternoon with radiative heating, which will
allow for mostly popcorn convection. Two things that will
locally lower severe potential today will be effective shear of
only around 20kts on the high end with evidence of a couple
capping inversions at 500mb and 600mb with plentiful dry air in
the upper levels. Realizing any low-probability severe threats
will be reliant on the breaking of these caps and ingestion of
bountiful dry air for downburst winds (900 J/kg environmental
DCAPE). While not impossible, this remains quite low probability
with no definitive forcing mechanism. Because of shallow
convective development, warm rain processes will dominate in
1.5" PWATS, so flooding could not be written off , but only
around 5% of ensemble guidance shows amounts exceeding FFGs
somewhere, depending on training or up-shear growth (mean
corfidi vectors of 8kts).

In areas where it does not rain, there will be moderate heat
risk into this afternoon, with chances of heat indices roughly
>50% in the valley/urban locations. Much of the ensemble spread
encompasses highs between the upper 80s and low 90s.

Into tonight, convection chances drop off to less than 10% with
a loss of mixing and unstable, surface-based profiles. Just a
few high clouds should not limit radiative cooling as
temperatures drop to near their respective dews in the lower 70s
and upper 60s. This will lend on to another night of fog
potential most likely for the river valleys. There is a >50%
chance of lows >70F in eastern OH, the lowlands of northern WV,
and far southwest PA which will provide little heat relief
overnight.

&&

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

- Heat risk increases to major for most of the area Saturday.
- Slightly higher severe wind threats and flash flooding
  threats Sunday.
----------------------------------------------------------------

The environment will be similar Saturday with perhaps a bit more
ridging in the flow pattern and upper subsidence, keeping
convective initiation a bit lower probability, but the
conditional probability of severe wind slightly higher. HREF
soundings show 1000 to 1500 J/kg MLCAPE with DCAPE up to 1000 to
1100 J/kg, but with the low probability of deep convection in a
stout dry layer with no definitive forcing, this may be
difficult to tap into. The highest chances of realizing the
threat are in east- central Ohio with a low- to-medium
probability of a pre-frontal trough passage. Once again,
flooding threats remain relatively lower with perhaps a bit
shallower low-moisture profile and very isolated shower/storm
coverage. On the contrary, with PWATS again near the 75th to
90th percentile, warm rain processes, and up-shear vectors of
>5kts, it could not be ruled out completely.

HREF shows a chance of heat indices pushing 95F to 100F during
peak heating Saturday in areas that do not experience rain
under the upper ridging, with brings heat risk into the major
category but with values slightly below advisory criteria.
Nonetheless, heat impacts will again be the most prevalent in
urban and valley areas. Little relief is expected overnight yet
again with NBM showing a >50% chance of lows >70F in eastern OH,
the lowlands of northern WV, and far southwest PA.

More organized severe and flooding threats materialize Sunday
with the approach and passage of a weak front. The major
difference as this front approaches will be the increase in
moisture, and the erosion of the mid level dry air. This might
make the chance of storms themselves higher, but the conditional
probability of a storm being severe slightly lower. Unlike the
two days prior, this forcing will be a mode for initiation in an
environment that is preconditioned with 1000 to 1500 J/kg
MLCAPE and ensemble mean 700 J/kg DCAPE. This may be marginally
enough to allow for a downburst wind threat. SPC has issued a
day three marginal risk.

As for flooding, the moisture push will likely take PWATS back
towards or higher than the 90th percentile with corfidi up-
shear/down- shear vectors of near or less than 5kts. Again, with
a deep warm later, 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.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
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 mid-level shortwave is still timed for passage at some point on
Monday, but there remains some relatively modest differences on
timing - with some ensemble members pushing the axis through during
the morning, and others lagging it into the afternoon. This would
suggest that a west-to-east PoP gradient is called for, which the
NBM does suggest, with highest (50-60%) values 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.

A drier pattern still appears likely Tuesday and Wednesday under
surface high pressure and rising 500mb heights, although diurnal
showers/storms may be possible Wednesday on an isolated basis.
Increasing southwest flow will help to bring the heat and humidity
back up for both days as 850mb temperatures run back up to 19C to
20C. Probabilities of 90F or greater max temperatures increase to
50%-70% on Tuesday and 70%-90% on Wednesday away from the ridges,
again highest in the urban and valley areas. 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 ameliorate the heat index values as compared to
Wednesday.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
Thunder mentions remain more limited this round, confined
mostly to real time updates of more stout updrafts. On the
whole, is is more likely a port does see a shower than if it
does, with PoPs generally less than 30%, and probabilities of
thunder at any given port generally less than 20%. Nonetheless,
there is a chane of a very isolated shower or storm this
afternoon impacting a terminal, most likely from 20Z to 00Z,
with the highest chances for eastern terminals (AGC, MGW, LBE,
DUJ).

Cu will dissipate after sunset, giving way to patchy high clouds
with winds decoupling and becoming light and out of the
south. Some fog is possible once again with bountiful moisture
and calm winds, though only noted at DUJ for now given highest
confidence. Should other vis restrictions creep in, it would be
most likely for eastern ports; probability of fog would increase
should any port be impacted by a shower to storm today.

Formation of fair weather cumulus is again forecast into the day
on Saturday after mixing ensues. Additional storm and shower
chances appear after 18Z, though coverage may be lower than the
day prior with low confidence in exact location.

Outlook...
Vis restrictions Saturday night may be more dependent on which
ports see rain the day prior. Rain would lend to a higher chance
of morning fog or haze.

More significant upper-level and surface boundary movement
appears to arrive Sunday, which will create a better focused
period for convection and restriction development.

&&

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

&&

$$

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