929
FXUS61 KPBZ 211211
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
811 AM EDT Tue Jul 21 2026

.WHAT HAS CHANGED...
Flood Watch issued for portions of the region from 1pm today to
11pm.

&&

.KEY MESSAGES...
1) Enhanced Risk for severe weather on Tuesday; Slight Risk for
Excessive Rainfall.

&&

.DISCUSSION...
KEY MESSAGE 1...
A large-scale low pressure system is currently tracking through
the Great Lakes early this morning. Over the last 24 hours two
mesoscale convective systems (MCS) have developed, one over Iowa
and currently tracking into Missouri and one north of Lake
Erie. Recycling of moisture from these remnant MCS`s will likely
redevelop showers and thunderstorms in the next 4 to 12 hours
across the Ohio River Valley. Warm and humid air (low 70s dew
points) fuel instability estimates that range from 1500 J/kg on
the low end to reasonably high end expectations near 2500 J/kg.
This in combination with strong wind shear (35-45 kts of 0-6km
shear) will create a favorable environment for organized
thunderstorms. The Enhanced Risk that has been issued by the
Storm Prediction Center 2 days ago is still in effect with
little to no change.

The most likely timing of severe weather remains between
12-8pm. Models suggest activity begins late morning or midday
along a remnant outflow boundary. Storms are then increasingly
favored further south and east across Pittsburgh and the I-70
corridor into the afternoon before convective coverage begins to
wane after sunset.

The primary threat from storms today remains damaging wind
gusts along some kind of developing squall line although
tornadoes and large hail remain possible in isolated supercells
that could develop out in front of the main line.

Another threat from this activity remains heavy rain. PWATs are
expected to be above the 95th percentile and could reach up
towards the daily maximum values (1.96 inches). This accompanied
with a relatively high freezing level will allow for efficient
warm rain processes in a very moist environment. Therefore, rainfall
rates could range between 3-6 inches per hour at times. Storms
are expected to be rather progressive, which would favor flash
flood concerns requiring training or multiple rounds of rain in
the same area. A Flood Watch has been issued for portions of
our region between 1pm and 11pm today due to this noted threat.
Counties could be added or removed through the evolution of this
event.

Expect lingering showers and non-severe thunderstorms into
early Wednesday before a cold front tracks through the region.

The potential for precipitation remain lows through the
remainder of the work week and into the weekend before showers
and storms again look possible on Sunday.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
The morning will continue to show some fog and low cigs through
14Z before a few nonsevere thunderstorms move through. Winds are
expected to gust up to 30 knots outside of thunderstorms during
the afternoon.

The best potential for strong to severe storms remains in
effect from 18Z to 23Z today with the passage a large low
pressure system. TEMPOS have been added to highlight vis and cig
restrictions with passing -TSRA in the region. PROB30s were used
through 21Z given the uncertainty behind the initial line.

Between 00Z and 06Z Wednesday shower and storm intensity and
coverage will decrease with increasing subsidence in the mid-
levels. By the 06Z to 12Z period  Expect to see some fog and
low cigs to develop through dawn tomorrow with some below IFR
conditions possible.

Outlook...
There may be some MVFR cigs in the vicinity of DUJ/FKL early
Thursday morning with cool northerly flow. Otherwise, VFR
conditions will prevail under high pressure into Friday.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch from 1 PM EDT this afternoon through this evening
     for PAZ021-029-031-073>076.
OH...Flood Watch from 1 PM EDT this afternoon through this evening
     for OHZ049-050-058-059-068-069.
WV...Flood Watch from 1 PM EDT this afternoon through this evening
     for WVZ001>004-012-021-509>514.

&&

$$

DISCUSSION...Hefferan
AVIATION...Shallenberger