PBZ issues Area Forecast Discussion (AFD) at Sep 22, 2:51 AM EDT
421
FXUS61 KPBZ 220651
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
251 AM EDT Mon Sep 22 2025
.SYNOPSIS...
Above normal temperature is expected ahead of a developing upper
level low, which may spawn increased shower and thunderstorm
chances through Monday. This system will be slow to exit the
area, resulting in daily rain chances through the end of the
week.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
KEY MESSAGES:
- Scattered showers around overnight
- Lows near 10 degrees above normal
---------------------------------------------------------------
Convection along a 700 mb wave sliding northeast through the
Ohio Valley has struggled as it moves into east-central Ohio
this evening with outflow surging well ahead of the decaying
cluster of storms and cutting off inflow. Redevelopment along
the outflow has been nearly nil, and the surface is now
stabilizing with sunset and rapidly diminishing any severe
weather potential. The latest RAP still suggests 500-1000 J/kg
of MUCAPE present over the next several hours. With remnant
outflow around, combined with additional shortwave movement,
this may provide enough lift for areas of showers and a few
rumbles of thunder to continue mainly west of I-79 overnight.
Otherwise, a blanket of cloud cover and 5-10 mph southerly flow
will keep low temperatures well above normal to the tune of 8-10
degrees across the board only settling into the low to mid 60s.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH TUESDAY NIGHT/...
KEY MESSAGES:
- Rain chances increase tonight with a warm front
----------------------------------------------------------------
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 Monday 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 25kts) 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.
Potential for showers and thunderstorms are likely to continue
overnight Monday into Tuesday as the shortwave traverses the
region, ensuring most locations are likely to see measurable
rainfall. Increased cloud cover will limit heating Tuesday to
keep area CAPE likely below the 1000 J/kg threshold for severe
concerns given shear will remain sub-optimal. Brief shortwave
ridging between shortwave movement likely will yield a drier
overnight period Tuesday night.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
KEY MESSAGES:
- Elevated precipitation chances through Saturday
- Near average temperatures
------------------------------------------------------------------
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.
&&
.AVIATION /07Z 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...Frazier
NEAR TERM...Frazier/MLB
SHORT TERM...Frazier
LONG TERM...Hefferan
AVIATION...WM/88
Source: PBZ issues Area Forecast Discussion (AFD) at Sep 22, 2:51 AM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202509220651-KPBZ-FXUS61-AFDPBZ)
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