840
FXUS61 KPBZ 220547
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
147 AM EDT Tue Jul 22 2025

.SYNOPSIS...
Dry and less humid weather will continue today under high pressure.
Increasing warmth and humidity is expected to return for mid to late
week. Shower and thunderstorm chances return Friday and Saturday
with an approaching cold front.

&&

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

- Dry and less humid weather continues
---------------------------------------------------------------

Surface high pressure will continue to be centered across the
eastern Great Lakes and Upper Ohio Valley region today. Dry
N-NE flow around the high should result in dew points near or
slightly lower than those observed on Monday. Mostly sunny
skies are expected, with a few cirrus clouds and diurnal cu.
Highs are expected to be near seasonable levels.

&&

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

- Dry weather through Thursday
- Building heat and humidity returns
----------------------------------------------------------------

High pressure will maintain dry and seasonable weather tonight
as it slides slowly eastward. The surface flow will veer to the
south on Wednesday on the western side of the high, as 500mb
ridging (500mb heights from 592-594dm) also builds across the
Upper Ohio Valley region. Dew points should also begin to
increase Wednesday under southerly flow. Heat indices are
expected to range from 90 to 95 across much of the area south
of I-80 and outside of the ridges.

500mb heights are progged to increase to 594-595dm on Thursday,
as 850mb temperatures rise to 20-21 deg C. This should result
in Thursday being the hottest day of the week. Dew points are
also expected to increase to around 70 for much of the region.
The combination of heat and humidity will result in heat
indices ranging from 95 to 100 for much of the region. These
values will be approaching heat advisory criteria (100-105 deg
F.)

The ridge is progged to break down and shift southward Thursday
night, though dry weather is expected to continue. Clouds will
increase late as a shortwave trough approaches from the
Midwest.

&&

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

- Shower and thunderstorm chances return Friday through Sunday
- Mainly dry Monday
- Warm and humid through the period

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

Model ensembles indicate an initial shortwave trough, and its
associated surface cold front, will cross the region on Friday,
with increasing shower and thunderstorm chances through the
day. Ensemble based precipitable water is expected to range
from 1.8 to 1.9 inches during the day, with MU CAPE from
1500-2000 j/kg. ML indicates some potential for strong to
severe storms on Friday, with a potential for flooding as well.
Will monitor the trends over the next couple of days.

The surface front is expected to stall across the region Friday
night through Saturday night, as another shortwave tracks from
the Midwest to the Upper Ohio Valley region. This will maintain
shower and thunderstorm chances, with the greatest coverage in
the afternoon and evening.

Maintained chance POPs on Sunday, with uncertainty in the
timing of the shortwave passage. Some ensembles indicate a
later passage, that would keep shower/storm chances lingering
into Sunday.

Surface high pressure is expected to briefly build across the
region Monday under NW flow aloft. Mainly dry weather is
expected, though warm and humid conditions will continue.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
High pressure has settled into the area and dry conditions are
expected through the TAF period. Cloud cover will largely be
only due to passing cirrus. There does seem to be a chance of
some smoke being in the atmosphere for the coming day from
wildfire. Through the morning hours, there is a chance of some
river valley fog developing. This does have the potential to
drop a few terminals to MVFR but this usually only remains for a
30 minute period at best. Thus will keep the mention of fog this
morning in the AFD. Winds will be light and variable through the
day.


Outlook...
High confidence in VFR and dry weather through Thursday
under the influence of high pressure. Strong radiational nighttime
cooling may be enough to support localized river valley fog that
impacts typical river valley terminals during pre-dawn hours
each morning through Wednesday.

&&

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

&&

$$

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