784
FXUS61 KPBZ 161812
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
212 PM EDT Thu Jul 16 2026

.WHAT HAS CHANGED...
Updated aviation discussion. Increasing confidence in
thunderstorms on Saturday, some of which could be severe.

&&

.KEY MESSAGES...
1) Above normal temperatures, smoke, and isolated storms persist
through week`s end.

2) More widespread storm chances, along with severe and flooding
risks, return on Saturday.

&&

.DISCUSSION...
KEY MESSAGE 1...
With surface and deep layer column flow orienting more northwest to
southeast on Thursday and especially Friday, ground-level wildfire
smoke from fires originating in southern Ontario and northern
Minnesota will arrive to our area. Upstream observations show the
worst of the visibility dipping down to as low as half a mile with
general prevailing conditions between 1-2 miles. In addition, air
quality is greatly degraded. The thickest ground-level concentration
will arrive late Thursday into Friday. In coordination with OH, PA,
and WV Departments of Environmental Protection, Air Quality Alerts
are in place for Thursday. Refer to your state`s department for more
information.

Meteorologically, increased smoke concentration will shave off a
couple degrees on high temperatures, which will help limit the heat
risk. Maximum heat indices should top out in the mid to upper 90s on
Thursday with lesser concerns Friday into the weekend.

There will also be a slight chance for showers and storms primarily
confined south of I-70 on Thursday. Mid-level ridging still remains
firmly entrenched locally with lobes of vorticity displaced to our
north and east, so overall forcing for ascent looks largely driven
by differential heating on the periphery of the smoke plume. On
Wednesday, the same feature produced clusters of thunderstorms
across northeastern PA, and CAMs seem to be suggesting similar
development today. Storm initiation will be the big question mark as
on the clear side of the smoke, MLCAPE values nearing 3500 J/kg with
30 knots of deep layer shear will be present. So a conditional, non-
zero severe weather risk is in play, and SPC has maintained a
Marginal Risk (1/5) south of I-70.

KEY MESSAGE 2...
Friday into Saturday the ridge over the Plains will break down and
the ridge axis will retreat westward over the Rockies. As this
occurs, a shortwave trough will quickly move through the larger
trough sitting over eastern Canada. Ensemble members are in
agreement that the axis of this shortwave will cross from the the
Great Lakes from NNW to SSE during the first half of the day
Saturday. On the eastern side of the trough axis, an upper-level
west-to-east oriented jet streak will intensify. Forcing from both
the approaching shortwave axis and the right entrance region of the
upper-level jet streak appear to be present in the region Saturday
afternoon, along with favorable environmental parameters for
convective hazards.

Instability in the region remains contingent on potential convective
development over the lower Midwest on Friday. Current CAMs suggest
convection will develop over northern IL, IN, and OH along a
boundary of differential heating influenced by the extent of
wildfire smoke. The uncertainty in the factors surrounding this
convection has led to disagreement between ensemble members on the
impact to the convective environment on Saturday. The deciding
factor will be the persistence of cloud cover from Fridays
convection into the day Saturday.

The 25-75th NBM percentile spread of surface CAPE is in excess of
1000 J/kg at 18z Saturday, indicating that some members prefer
persistent cloud cover while others expect early clearing. In the
scenario where persistent cloud cover prevents maximized heating,
the existing thermodynamic environment will still favor convective
development, meaning all severe hazards cannot be ruled out in any
scenario. If clearing occurs in the morning, destabilization will
occur earlier and result in a more potent severe threat. Regardless
of the level of clearing, favorable thermodynamics in the same
region as upper-level forcing will likely result in convective
development.

While all hazards are on the table, wind and flash flooding look to
be the primary threats. Current model soundings for Saturday
show plentiful deep layer moisture and a favorable warm rain
layer through 400mb, meaning hail development is less favorable.
PW values near 2 across most models indicate high confidence
in heavy rainfall production in sustained updrafts. Elevated dew
points resulting in low LCLs pose a non-zero tornado threat,
but low-level shear is relatively weak which could be a
limiting factor.

SPC has outlined the area in a slight risk for severe weather and
WPC has outlined the area in a marginal risk for excessive rainfall
for Saturday.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
The main impact to aviation will be smoke restrictions from
Canadian wildfires in NW flow. IFR was already occuring north of
PIT, and this will continue tonight. Elsewhere, expect a gradual
decrease to IFR vsbys as smoke concentration increases. Some
sites were reporting cigs around 3.5kft, though this appears to
be a partial obscuration from smoke as opposed to stratocu.

Some limited improvement to MVFR vsbys in smoke is expected on
Friday as the flow gradually backs to the west.

Outlook...
Restrictions are likely late Friday night into Saturday night
with an initial warm front, then a crossing cold front. Showers
and thunderstorms are likely, and some storms could be severe
later Saturday. VFR returns Sunday and Monday under high
pressure, with restrictions possible in showers and
thunderstorms with a Tuesday cold front.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Air Quality Alert until midnight EDT tonight for PAZ007>009-
     013>016-020>022-029-031-073>078.
OH...Air Quality Alert until midnight EDT tonight for OHZ039>041-
     048>050-057>059-068-069.
WV...Air Quality Alert until midnight EDT tonight for WVZ001>004.

&&

$$

DISCUSSION...MLB/MIM
AVIATION...WM