425
FXUS61 KPBZ 180002
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
802 PM EDT Fri Jul 17 2026

.WHAT HAS CHANGED...
Increasing confidence in severe thunderstorms on Saturday with
upgrade to an Enhanced Risk for parts of our area.

&&

.KEY MESSAGES...
1) Smoke begins to clear tonight/Saturday morning.

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

3) Return to seasonable temperatures next week with more storms
possible on Tuesday.

&&

.DISCUSSION...
KEY MESSAGE 1...
Ground-level wildfire smoke will wane overnight and Saturday
morning as a result of a lifting warm front and rain washout.
Additional smoke may return early next week, but should be
noticeably less impactful.

KEY MESSAGE 2...
Friday into Saturday, the mid-level ridge axis will break down as a
potent shortwave enters the Great Lakes region quickly diving
southeast. Meanwhile, surface low pressure gradually deepens as
it follows a similar track. Locally, the pressure gradient will
tighten a bit in response ramping up southwesterly flow and
pulling in moisture to offset mixing some with afternoon dew
points likely in the low 70s and highs topping out in the mid
80s. As cooler mid-level air arrives with the wave, we`ll be
primed with a moist and unstable environment awaiting the lift
from the shortwave as well as a surface boundary which will be
responsible for two rounds of thunderstorms, both with severe
potential.

The first round will be driven by more broad ascent from the
shortwave and loose upper jet entrance region dynamics. Expect to
see scattered development fire off after noontime in an environment
with mean SBCAPE values from the REFS around 2500 J/kg and deep
layer shear values around 20-30 knots. Directional shear may be a
limiting factor to otherwise favorable supercellular mode with the
initial round, though some enhancement with locally backed surface
flow could elongate hodographs enough that a right moving storm
could become supercellular with all hazards on the table, though
hail likely is the least probable given rich deep layer moisture
with PWATs nearing 2".

By evening time, a surface front dives south across Lake Erie and
into our northwestern PA counties likely just a bit before sunset.
Ensembles suggest that there`s sufficient recovery in the wake of
any scattered afternoon thunderstorms to support maintenance and
intensification of storms along the boundary, and likely our prime
window for more widespread coverage and impacts. Despite timing
being after peak heating, mesoscale processes should allow for the
line to keep its strength as it moves through most of our area. Deep
layer column flow at this point will be unidirectionally westerly
which points toward rapid upscale growth of storms along the
boundary bringing a damaging wind threat. Despite 0-3 km shear
values nearing 30 knots, the line-parallel orientation suggests that
QLCS tornado potential should be rather low unless a surge occurs to
the east or localized cell mergers encourage localized supercellular
structures able to utilize environmental shear best.

Heavy rain will be a threat as well with high PWAT values and a
generally tall, thinner CAPE profile. However, with the progressive
nature of the storms along the front, a flash flooding threat would
likely be confined to urban areas and/or areas that receive several
rounds of rain both from the initial round and then as the boundary
moves through. Both HREF and REFS maximum one hour QPF peaks around
1.75" representing a worst case scenario hourly rainfall rate. This
does exceed one hour flash flood guidance in urban areas, so will
need to monitor this threat.

WPC has maintained the Marginal Risk of excessive rainfall. SPC has
upgraded the northern half of our area (roughly from PHD to PIT to
IDI on north) to an Enhanced Risk and leaving the rest of the area
in a Slight Risk.

KEY MESSAGE 3...
Mid-level northwest flow remains into early next week as West
Coast ridging stays amplified. Sunday and Monday will be dry
with lack of mid-level impulses and forcing, and temperatures
dip back to normal. Another shortwave arrives on Tuesday and
could bring with it a renewed severe weather threat. SPC has our
area outlined in the day 5 outlook, though uncertainty remains
both with timing and amplitude of the mid-level wave as well as
a surface cold front.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
Dry conditions prevail for most through 04Z, save ZZV, with IFR
smoke remaining in place for most ports. As winds shift out of
the south overnight, much of the near-surface smoke will be
allowed to exit the region, with overall improvements expected
between 03Z and 13Z for most (fastest recoveries for southern
ports).

Overnight, weak mid level lift may be enough to generate
isolated precip chances along a shortwave, but confidence
remains low. Some models allude to overnight storm potential,
but most of the smoke-forced ones squash this for now, tending
more towards widely scattered showers. Ports will primarily
remain VFR.

Into tomorrow morning, models then allude to a low-cloud deck
advecting in as dew point recover in most southwest flow. The
most likely scenario is an early day MVFR deck, which again,
there is a low chance of shower or storm development, most
likely north of PIT. Storms may bring gusty, erratic winds
should they occur.

This deck is expected to scatter and lift mid-day with mixing,
before thunderstorms chances again, overspread the area in the
later afternoon into evening hours as a cold front comes down
from the north, with the highest chance of organized convection,
erratic winds, and cig/vis restrictions overspreading the area
from 20Z to 02Z from north to south.

Outlook...
Temporary visibility restrictions are possible Sunday morning
before VFR returns Sunday and Monday under high pressure.
Restrictions return in showers and thunderstorms on Tuesday with
a 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 Saturday night for
     WVZ001>004-012-021-509>514.

&&

$$

DISCUSSION...Rackley/MLB
AVIATION...Milcarek