005
FXUS61 KPBZ 271140
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
740 AM EDT Mon Jul 27 2026

.WHAT HAS CHANGED...
The risk of an MCS moving through the region is trending
downward (details below) with a limited severe risk for
Tuesday. Added a quick highlight to note the rest of the week
pattern that is light on impacts. Aviation discussion updated
for 12z TAF issuance.

&&

.KEY MESSAGES...
1) Varying degrees of severe threats and thunderstorm timing
this afternoon into Tuesday morning.

2) Lowering severe threat for Tuesday but non-zero probability
remains favor far southeastern zones.

3) Generally dry and seasonable temperature favored into the
start of the weekend.

&&

.DISCUSSION...
KEY MESSAGE 1...
The broad overview notes that embedded shortwaves within NW
flow between the Central Plains ridge and eastern seaboard
trough will travel SE through Tuesday morning and offer
increased thunderstorm chances starting this afternoon.

Through the early evening, hi-res model guidance has seemingly
narrowed the area of focus to northwest PA where the uncapped
environment (nearing 2000 J/kg) receives enough lake-breeze
lift to trigger initiation whereas everywhere else lacks such
forcing mechanism to get storms started. Enough shear (around
30kts) plus DCAPE around 800 J/kg would allow any developed
storm to create a downburst damaging wind threat; resultant
outflows would then be the source of storm coverage expansion
S/W/E through 00z. The lack of strong forcing aloft and greater
organization methods alludes to only isolated instances of
damaging wind (and small hail) that would translate to a
"Marginal Risk" outlook from SPC.

The "greater threat" leading into today was MCS potential after
00z/8pm that has garnered the "Slight Risk" SPC outlook. Latest
model trends more favor this threat to remain west of the region
as it dives west into the more unstable airmass, leaving this
area in the convective cirrus shield less conducive to severe
potential. The approaching mid- level shortwave may still
initiate overnight thunderstorms but these are likely to be more
elevated (thus greatly reducing the damaging wind risk) and
less organized. The MCS also could produce an outflow wind that
reaches the area that could aide convective initiation, but it
would still remain tough to see this reaching higher severe risk
levels beyond an isolated instance of damaging wind.

This is a lot to just say that afternoon storms are mainly
favored in NW PA with the more widespread threat being
determined by the path a MCS takes after forming in the western
Great Lakes region.


KEY MESSAGE 2...
Timing will be key in severe weather potential Tuesday as
forcing/lift sees a significant uptick with the passing cold
front and stronger shortwave trough either in the morning hours
(lesser severe threat) or early afternoon hours (greater severe
threat for southeast zones). And even this simplified projection
doesn`t account for convective evolution late tonight into early
Tuesday morning.

In the latter scenario, the general lack of overnight convection
plus afternoon frontal arrival allows for greater buoyancy
buildup (approx. 1500 J/kg SBCAPE) to better manifest a
straight-line damaging wind threat as storm clusters form along
the advancing front. Severe probabilities would be lowest from
NW PA to NE OH but slowly trend up progressing southeast toward
the mid-Atlantic.

In the former scenario, the combination of overnight convection
and/or faster frontal movement results in most storm activity
occurring during lower buoyancy hours and exits prior to Tuesday
afternoon. An isolated damaging wind gust couldn`t be ruled out
but is only likely to occur near Preston/Tucker Counties. The
rest of the day may still see scattered showers and isolated
thunderstorms due to residual lift in NW flow near the cold-
core upper trough center but SBCAPE values generally less than
1000 J/kg make it difficult for severe threats to occur.

Either scenario has a low-end flash flood threat thanks to
PWATs around the 90th percentile, favoring poor drainage or
low-lying areas, and is more likely to occur if storms maximize
plus repeatedly hit similar spots.

KEY MESSAGE 3...
Seasonable temperature and a trend toward dry weather is favored
the rest of the week as the region remains under cooler NW flow
between staunch NW troughing and central plains ridging. There
is potential for wrap-around moisture from the New England low
to keep lower probability storm chances through Thursday
(favoring the higher terrain) that should be monitored for
changes if you have planned outdoor activities.

The next widespread chance for convective activity will be
sometime over the weekend with reinforcing upper shortwave
trough movement but early pattern indications suggest a pretty
limited hazard risk.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
A foggy start to the day (including some patchy dense fog)
improves to VFR everywhere by mid morning and remains VFR
through the majority of the TAF period. No major edits made to
mentions of rain/thunder as hi-res models haven`t changed much
over recent runs. For this afternoon and early evening, favored
thunderstorm development mainly in northwest PA (FKL/DUJ) off a
lake breeze, with potential for storms migrating/developing SE
into western and SW PA with resultant convective outflows.

Convective outlooks remain uncertain after 22z due to their
reliance on the path/effects of upstream thunderstorms or
mesoscale convective systems moving from the western Great Lakes
into the Ohio Valley. Maintained a similar trend as recent TAF
cycles, which assumed MCS activity remains west of the region
but included an uptick in storm development later in the night
(near/after 06z) as an outflow boundary and mid-level shortwave
move across the local area through early Tuesday morning.

Outlook...
Moisture convergence ahead of an incoming trough/surface cold
front may result in MVFR to locally IFR conditions even outside
of convection Tuesday morning. Thunderstorms are likely
along/ahead of the boundary with potential for showers to linger
in the post-frontal environment due cold NW flow aloft
maintaining some buoyancy.

High pressure builds through the mid-week period to increase the
duration of VFR periods with dry weather, with any restrictions
mainly occurring during the morning hours.

&&

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

&&

$$

DISCUSSION...Frazier
AVIATION...Cermak/Frazier