387
FXUS61 KPBZ 162319
AFDPBZ

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

.WHAT HAS CHANGED...
Decreased confidence in severe convection tonight with smoke
becoming too thick to allow for convection. Will need to be on
the lookout for isolated instances of very dense fog come
morning in river valleys given smoke concentrations.

&&

.KEY MESSAGES...
1) Smoke, and visibility obstructions persist through tomorrow.

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 and Friday. Refer to your state`s
department for more information.

One thing to note, with low temperatures forecast within a few
degrees of dew point temperatures, the potential for localized
"super fog" with very low visibilities (<1/4 mi) will need to be
monitored in river valleys Friday morning with plenty of smoke-
related CCN for water drops to condense onto. Should this occur,
a dense fog advisory may be needed tonight, even if visibility
interruptions are on a localized basis.

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 /00Z FRIDAY THROUGH TUESDAY/...
The main impact to aviation will be smoke restrictions from
Canadian wildfires in NW flow. For ports in western PA, IFR vis
has already been (or nearly been) noted. Elsewhere, expect a
gradual decrease to IFR vsbys as smoke concentration increases.
Some sites were reporting cigs around 2.5kft, though this
appears to be a partial obscuration from smoke as opposed to
stratocu.

Most updates to this forecast matched real time observations to
the latest smoke modeling. For most ports, visibilities are
forecast to drop faster and farther than the prior update, with
some half mile visibilities possible at daybreak as smoke gets
thicker with the boundary layer decoupling, and fine particles
trapped near the surface.

One particular concern of note will be to keep an eye on the
potential for "super-fog" to develop locally as temperatures
approach dew points for river valleys and plentiful smoke to
allow for efficient condensation. Upgrades to dense or very
dense fog may be needed in real time should this occur.

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 Friday night for
     PAZ007>009-013>016-020>022-029-031-073>078.
OH...Air Quality Alert until midnight EDT Friday night for
     OHZ039>041-048>050-057>059-068-069.
WV...Air Quality Alert until midnight EDT Friday night for
     WVZ001>004.
     Air Quality Alert from midnight tonight to midnight EDT Friday
     night for WVZ012-021-509>514.

&&

$$

DISCUSSION...MLB/Milcarek
AVIATION...WM/Milcarek