976
FXUS61 KPBZ 302336
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
736 PM EDT Mon Jun 30 2025

.SYNOPSIS...
Scattered showers and thunderstorms expected this afternoon and
again on Tuesday. A few storms could produce damaging winds and
localized flooding. Dry weather with slightly above normal
temperatures returns through Saturday save a chance of showers
and storms on Thursday.

&&

.NEAR TERM /THROUGH TUESDAY/...
KEY MESSAGES:

- Scattered strong to severe thunderstorms with heavy rain
  possible this afternoon and evening.
- Muggy overnight with some areas of fog possible.
---------------------------------------------------------------

A stalled boundary will lift north as a warm front today with
increasing showers and thunderstorms in the warm sector aided by a
passing mid-level shortwave. The environment will look a bit
different today than the past several days with bit more shear be
available with marginally increasing low and mid level flow,
especially north of Pittsburgh. The morning showers and scattered
cloud cover may mute the environment some for a severe threat
farther north, but the 12z HREF still suggests a 60-70% chance of
SBCAPE >1000 J/kg and 30 knots of deep layer shear by this
afternoon. Equilibrium levels are high with a deeper CAPE profile,
so wouldn`t be surprised to see better updraft cores today. This
environment supports the chance for more organization in convective
development potentially into broken line segments capable of
damaging wind and marginally severe hail, though think the hail
threat is lower given the saturated profile not supporting hail
maintenance. There will also be a low, but not zero, tornado threat
confined to around the US-422 to I-80 corridor in closest proximity
to the surface boundary. Increasing south/southwest 925-850 mb flow
atop south/southeasterly surface flow will elongate the lower part
of the hodographs suggesting a bit higher potential for streamwise
vorticity ingestion in favorably south/southeasterly right
movers. STP there nudges up to 0.3-0.7.

The other threat will be heavy rainfall with deep layer southerly
flow pumping in PWAT values nearing 2 inches. What might help us
mitigate a significant excessive rainfall threat is upwind
propagation vectors in the 15-20 knot range rather than <10
knots and a deeper CAPE profile suggesting warm rain processes
might not be as dominant as previous days. Still, with those
PWATs, HREF probability for >1"/hour rates is as high as 50% in
northwest PA, specifically Lawrence, Mercer, and Venango
Counties, as well as in the PA ridges. So, have opted to go with
a flood watch through 10pm tonight to cover this threat
especially given our relatively hydrophobic conditions with
recent rainfall.

Convective activity likely wanes after sunset and gives way to a
warm and humid overnight period with lows 8-10 degrees above normal.
Some fog is possible in sheltered areas and valleys that see rain
today, but elevated wind likely precludes most development.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
KEY MESSAGES:

- Showers and thunderstorms with another risk for severe and
  heavy rainfall Tuesday.
- Temperatures climb a bit with drier weather on Wednesday.
----------------------------------------------------------------

Another round of showers and storms will develop on Tuesday along
and ahead of a passing cold front and mid level trough. Some
uncertainty arises with potential morning convection along a pre-
frontal trough, especially in northern WV and southwest PA. Not all
CAMs have this, but if it does develop, it could taint the local
environment ahead of the afternoon FROPA. What else it could do is
enhance the flooding threat in the same area with several rounds of
showers and storms in a still tropical-like environment with near 2"
PWATs. Faster storm motion should again preclude more notable flood
threats, but the environment will support heavy rainfall.

With the frontal passage, HREF prob for 1000 J/kg SBCAPE and 30
knots of deep layer shear reaches 70-80%, so again a favorable
environment to support organization and a damaging wind threat.
Highest probability for severe at this point looks to be north of
Pittsburgh, but with morning uncertainty that threat could shift
farther south. SPC has maintained the expanded Marginal Risk (1/5)
as far back as DUJ to PIT to HLG.

A dry day comes Wednesday in the wake of the front with surface high
pressure nosing in from the west. Dew points come down back into the
low to mid 60s but temperatures are still likely to breach 85F for
highs with up to an 80% chance in southeast Ohio and the
southwest PA urban areas.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
KEY MESSAGES:

- Cold front Thursday brings back showers and storms.
- July 4th holiday looks dry.
- Rain chances return late next weekend.
-------------------------------------------------------------------

A shortwave will churn through the ECONUS longwave trough on
Thursday and kick a cold front through the area from the northwest.
Timing remains a bit uncertain, but passage is likely some time late
morning to mid-afternoon which will return the chance for showers
and storms. It remains unclear how much effect the high and
associated lingering subsidence may have as the front butts up
against it. Dew points ahead of it look to sit in the low 60s with
not much return flow on Wednesday, but the NBM prob for >1000 J/kg
SBCAPE is around 50-60% in the afternoon hours. Deep layer shear may
be the lacking component with the best forcing and flow displaced to
the north with the shortwave. Still, machine learning does peg at
least a low-end chance of severe weather with the passage,
contingent on it being at a favorable diurnal time.

Headed into the fourth, ensembles are in good agreement on a return
of mid-level ridging behind the departing longwave. Some subtle
timing differences arise with how quickly the ridge builds which
suggests that high temperatures are lower confidence right now, but
some of the MaxT spread has decreased with a trend toward a warmer
solution in the mid to upper 80s. Rain chances are low in any
scenario at less than 20% with dry air advecting in in the wake of
Thursday`s boundary.

The ridge flattens out into the weekend with a mid-level zonal flow
pattern taking over. Ensembles do agree on low pressure development
across the Northern Plains sometime Friday into Saturday and quickly
sliding east, but disagreement on timing lends low confidence
precipitation chances locally as the attendant surface cold front
follows along with it. Most of Saturday looks dry at this time with
even the faster solutions holding precip chances off until early
Sunday, so most likely will see a more unsettled pattern return for
the latter half of the weekend and into next week. Temperatures
around average through the second half of the week may warm to
slightly above average for the weekend.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
Several rounds of showers and thunderstorms are expected through
this evening in a very moist airmass behind a warm front. Brief
periods of heavy rainfall/IFR visibility and gusty winds will be
possible in the heavier storms. Kept 2-3 hour TEMPO groups to
illustrate most likely timing for additional waves before
activity eventually begins to taper off with the loss of
diurnal instability and as the shortwave exits. Left VCSH at
most sites into overnight hours due to uncertainty regarding
precip end times. Lingering low-level moisture will lead to an
MVFR/IFR stratus deck overnight, with enough mixing remaining to
keep widespread fog from developing. Slow improvement is
expected after sunrise, followed by an additional round of
showers and thunderstorms late morning through afternoon with
an approaching cold front.

Outlook...
VFR returns Wednesday under high pressure, before restriction
and thunderstorm potential returns with a Thursday cold front.
VFR is expected again by Friday under high pressure.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch until 10 PM EDT this evening for PAZ007>009-
     013>016-020>022-073>078.
OH...None.
WV...None.

&&

$$

SYNOPSIS...MLB
NEAR TERM...MLB
SHORT TERM...MLB
LONG TERM...Rackley/MLB
AVIATION...Cermak/CL