PBZ issues Area Forecast Discussion (AFD) at Sep 22, 5:40 AM EDT
169
FXUS61 KPBZ 220940
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
540 AM EDT Mon Sep 22 2025
.SYNOPSIS...
Above normal temperatures are expected ahead of a developing
upper level low, which may spawn increased shower and
thunderstorm chances later this afternoon and evening. This
system will be slow to exit the area, resulting in daily rain
chances through the end of the week.
&&
.NEAR TERM /THROUGH TONIGHT/...
KEY MESSAGES:
- Scattered showers around through dawn
- A Marginal Risk of severe weather is possible today
---------------------------------------------------------------
The day will begin with a few showers over the area this
morning. This may impact the potential for significant
destabilization but the ensembles do show a bit of a break in
the convection by midday.
The first in a series of shortwaves amidst the gradual
development of a sagging trough (and potential cut off low) is
expected to encroach the region this afternoon and evening.
This jet-induced lift combined with a seasonably warm and moist
airmass is likely to lead to scattered to locally numerous
discrete thunderstorms that favor locations generally to the
west and north of the I-79 and I-70 interchange. Modest CAPE
(~1200 J/kg) and weak shear (around 30kts) are enough to
support a low-end damaging wind threat along with heavy rain
potential, though dry antecedent conditions and fast enough
storm-motion should stunt any flood concerns. In fact, hi-res
cams suggest a decaying line of storms this evening.
Potential for showers and thunderstorms are likely to continue
overnight Monday into Tuesday morning as the shortwave
traverses the region, ensuring most locations are likely to see
measurable rainfall.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
KEY MESSAGES:
- Cloud cover will limit the heating on Tuesday but showers and
thunderstorms are still expected.
----------------------------------------------------------------
The increased cloud cover will limit heating on Tuesday to keep
area CAPE likely below the 1000 J/kg threshold for severe
concerns given shear will remain sub-optimal. Still a few
instances of thunderstorm wind gusts are still possible. Brief
shortwave ridging between shortwave movement likely will yield a
drier overnight period Tuesday night. By Wednesday, the cold
front has moved through the region leaving mush cooler
conditions for Wednesday. The amount of instability will be
minimal but showers will be expected through the day on
Wednesday.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
KEY MESSAGES:
- Elevated precipitation chances through Saturday
- Near average temperatures
- Mainly dry conditions return by Sunday.
------------------------------------------------------------------
A stalled trough positioned between the Great Lakes and the
Mississippi River Valley will bring the region periods of
clouds, rain chances, and near-normal temperatures through the
latter part of the week.
Ensemble guidance suggests Thursday into Friday may offer the
greatest potential for more widespread rainfall, supported by
enhanced jet dynamics tied to the trough. Increasing southwest
moisture transport will likely push PWAT values into the 1.5 to
1.7 inch range, with a deep warm cloud layer extending above
13kft. Rainfall totals from Thursday morning through Saturday
morning are expected to range from 0.4 to 0.75 inches, with
locally higher amounts (over an inch) possible, especially near
and within the ridges and south of Pittsburgh. Given dry
antecedent soils and sufficient shear to keep convective
progressive, the flood threat is considered 'low'.
Afternoon high temperatures will likely hold near the mid-70s
(close to average) during this time period, while overnight lows
trend about 5 degrees above normal due to elevated dew points
and limited radiational cooling. The extended wet pattern will
take a break by Sunday as the last of the moisture exits the
area leaving high pressure to infiltrate the region.
&&
.AVIATION /10Z MONDAY THROUGH FRIDAY/...
General VFR conditions are expected this morning along with
light, scattered showers associated with a crossing shortwave.
The exception is potential MVFR cigs at FKL and DUJ early this
morning. VFR is expected through much of the day ahead of
another approaching shortwave trough. The CU rule and model
soundings indicate a cumulus cloud layer will likely develop by
afternoon, with scattered showers also developing ahead of the
mentioned trough. By mid to late afternoon, thunderstorms are
possible, initially across Ohio. These should move eastward
through early evening, though there is some question on how far
east they get before outrunning the best instability. Went with
PROB30s for TAF sites given the uncertainty in instability and
overall coverage.
.OUTLOOK....
Restrictions in showers are possible into early Tuesday.
Otherwise, general VFR is expected until approaching low
pressure brings additional rain to the area Wednesday into
Friday.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...Shallenberger
NEAR TERM...Shallenberger
SHORT TERM...Shallenberger
LONG TERM...Hefferan/Shallenberger
AVIATION...WM/88
Source: PBZ issues Area Forecast Discussion (AFD) at Sep 22, 5:40 AM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202509220940-KPBZ-FXUS61-AFDPBZ)
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