Houston, Pennsylvania Weather Forecast Discussion

416
FXUS61 KPBZ 211556
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
1156 AM 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 /THROUGH TONIGHT/...
KEY MESSAGES:
- Dry for most areas, but incoming shortwave may foster showers
  and thunderstorms across eastern Ohio.
- These late day storms could have gusty wind with heavy rain.
---------------------------------------------------------------
The upper Ohio River Valley will remain wedged between upper
ridging/surface high pressure in New England and western Great
Lakes troughing. While southerly/southwesterly atmospheric flow
ensures above normal temperature this afternoon with subtle
moisture increases, the surface high is likely to suppress most
diurnally driven convection unless a single shower over the WV
higher terrain can effectively generate an outflow that spawns
additional updraft/storm development in the modest CAPE (~800
J/kg) and low shear (20kts) environment.
The notable exception to these conditions is the arrival of a
mid-level shortwave lifting NE from the OH/KY border late this
afternoon and evening. Convective models favor development of a
broken line cluster of storms moving through the far eastern OH
zones between 5pm-10pm before fizzling with deepening of the
nocturnal inversion. Outside of slightly high CAPE, the storm
environment will be similar as noted above along with 75th
percentile PWAT; its enough for a low probability risk of strong
wind and heavy rain but unlikely to see storms reach severe
thresholds.
While most convection ends overnight, additional shortwave
movement across eastern OH may provide enough lift ahead of a
weak warm frontal boundary for areas of showers to develop
mainly west of I-79.
&&
.SHORT TERM /MONDAY 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 SATURDAY/...
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 /16Z SUNDAY THROUGH THURSDAY/...
Surface high pressure centered over New England will favor
scattered to broken cu and wind veering to a more southerly
direction that occasionally gusts to 15-20kts (near 100%
likelihood) this afternoon. There remains a low probability for
a very isolated shower in western PA from 19z-23z, but
probability of terminal impact is too low for TAF mention. Of
higher confidence is weak upper shortwave movement to the west
that likely will spawn a broken line of convection (30-40%
probability for lightning) through the far eastern OH zones
between 22z-04z.
Hi-res modeling suggests any convection generally dissipates
after sunset; however, due to lift with that shortwave, it is
possible an area of showers continues to advance ENE overnight
to produce at least some light rain at area terminals. Even in
this wetter scenario, probability remains low (less than 30%)
for MVFR cigs to develop Monday morning.
.OUTLOOK....
A series of shortwaves will provide varying rain chances
through the middle of the week. While VFR is likely to be the
predominant flight category through this timeframe, periods of
heavier rain and/or patchy morning stratocu may result in MVFR
restrictions.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...Frazier
NEAR TERM...Frazier
SHORT TERM...Frazier
LONG TERM...Hefferan
AVIATION...Frazier

NWS PBZ Office Area Forecast Discussion