237
FXUS61 KPBZ 112311
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
711 PM EDT Fri Sep 11 2026

.WHAT HAS CHANGED...
A Flood Watch has been issued for part of the area on Saturday.
Increased heavy rain and gusty wind threat Saturday followed by
another severe weather threat on Sunday.

&&

.KEY MESSAGES...
1) Widespread rain and isolated thunderstorms expected on Saturday
with flooding possible

2) Potential for severe thunderstorms Sunday afternoon and evening
with a cold front

3) A brief bout of dry weather returns early next week

&&

.DISCUSSION...
KEY MESSAGE 1...
After a brief bout of shortwave ridging departs on Friday, deep
layer southwest flow strengthens on Saturday as a mid-level trough
approaches. Deep layer moisture increase is noted in both the HREF
and REFS with mean PWAT values near 2" which is above the 99th
percentile climatology for the day setting the stage for heavy rain
potential. MRMS soil moisture remains elevated across the region at
>50%. Increasing low-level warm advection and broad ascent
downstream of the trough should support a shield of precipitation
arriving from west to east in the late morning hours. Ahead of that
shield, CAMs fire off additional convection as convective
temperatures are reached. This could set the stage for a couple
rounds of heavy rain especially for the PA and WV ridges with the
initial convection and then the shield of precip shortly behind it.
HREF and REFS probability for >1" of rain through Saturday night
both exceed 80% east of Pittsburgh with a long-tailed distribution
extending farther west which suggests some localized convective
enhancement and higher amounts can`t be ruled out farther west
either. Again east of Pittsburgh, probability of >2" is as high as
70% and >3" as high as 40%, with HREF LPMM values nearing 6" and a
representation of a localized high-end scenario. For these reasons,
becoming increasingly concerned about flash flooding in the higher
elevation, and have issued a Flood Watch for far southeastern OH,
northern WV, and southwestern PA where the ensemble probabilities
are highest.

Perhaps with storm-scale processes as we lack a defined surface
forcing mechanism, CAMs suggest convective enhancement and even
some linear/bowing structure along with the initial push of
showers and storms in the late morning as it moves through
eastern OH and into western PA. Despite the deep layer moisture,
HREF joint probability for >1000 J/kg of SBCAPE and 30 knots of
deep layer shear is up to 80% across a bulk of eastern OH and
western PA. While the thermal profile shows more deeper, skinny
CAPE, can`t be blind to a severe threat, primarily wind, along
with the flooding. Should see the precip make its exit stage
right by midnight and just leave some scattered showers around
overnight.

KEY MESSAGE 2...
No rest for the weary as we face another severe threat again on
Sunday afternoon as a deeper mid-level trough approaches and slides
just off to our north. This will kick a surface cold front through
the Great Lakes and to our local area in the afternoon hours. Plenty
of surface moisture will be in place from Saturday`s rain, and light
southerly flow will reinforce the higher dew points as ensemble
means maintain upper 60s Saturday night through Sunday morning.
Primary uncertainty headed into the afternoon is how much clearing
we can get to destabilize. NBM 25th/75th spread in cloud cover at
11am ranges from partly cloudy to overcast, so the goal posts are
still wide. Consequently, NBM`s mean SBCAPE come 5pm sits around 900
J/kg, but the 25th percentile is as low as 300-500 J/kg and the 75th
percentile nearing 2000 J/kg. It`s likely not going to be a day
where we need to violently destabilize as deep layer shear will be
strong (35-45 knots) beneath an increasing belt of 40-60 knot
westerlies at 500 mb, and stronger forcing along the front should be
enough to overcome lower CAPE values. Interestingly, some members
within the LREF thermal profiles, as well as some deterministic
guidance, shows a subsident warm layer around 800 mb that pretty
effectively caps updrafts. This is likely a result of a stronger
surface ridge extending in locally from departing high pressure
off the New England coast. The latest RRFS does not have this
feature. So that will be another aspect to add to the
uncertainty in place still, and will see how future CAMs come
in.

KEY MESSAGE 3...
Albeit with some timing differences, the Sunday trough departs
sometime on Monday and will return a brief bout of dry weather
to start off the work week as mid-level ridging builds. Can`t
rule out a few showers continuing into Monday morning in a
solution with a slower, deeper departing trough, but in any
scenario, we should be dry by Monday afternoon.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
VFR and light winds prevail through tonight. Mid and high clouds
increase overnight and cigs lower to 3-5kft by Saturday morning
as an upper shortwave approaches the area. Restrictions become
more likely mid to late Saturday morning through the rest of
the day as showers and thunderstorms overspread the area. Some
storms could produce strong, erratic wind gusts. Outside of
storms, winds remain generally light and out of the south.

Restrictions are expected during the afternoon tomorrow and into
the evening hours. Have introduced some PROB30s to account for
thunderstorms between the 18Z and 00Z period. Some storms are
possible to linger in the 00Z to 06Z period, and this is the
case for the PIT TAF.

Outlook...
Restrictions will likely continue into early Sunday with
additional rounds of rain showers and thunderstorms with a
passing front.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch from Saturday afternoon through late Saturday
     night for PAZ008-009-014>016-021-022-029-031-073>078.
OH...Flood Watch from Saturday afternoon through late Saturday
     night for OHZ057>059-068-069.
WV...Flood Watch from Saturday afternoon through late Saturday
     night for WVZ003-004-012-021-509>514.

&&

$$

DISCUSSION...MLB
AVIATION...Shallenberger