Coolspring, Pennsylvania Weather Forecast Discussion

423
FXUS61 KPBZ 212317
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
717 PM EDT Sun Sep 21 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 MONDAY 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 MONDAY 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 /23Z SUNDAY THROUGH FRIDAY/...
A weak shortwave trough will cross the region tonight, with
scattered showers expected. Most of the thunderstorm activity
has diminished, and this trend should continue through the
evening with waning instability. General VFR conditions should
continue as most of the showers will be light, though more
favorable low level moisture is progged further north with MVFR
cigs expected to develop overnight at FKL and DUJ.
Other than morning MVFR at FKL and DUJ, VFR is expected through
much of the day Monday 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 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 TEMPO thunder for ZZV, which has the
highest probability of seeing thunder, with prob30s to the east.
.OUTLOOK....
Restrictions in showers are likely Monday night 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

NWS PBZ Office Area Forecast Discussion