264
FXUS61 KPBZ 190706
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
306 AM EDT Sat Jul 19 2025

.SYNOPSIS...
Showers and thunderstorms are expected to develop today along
with another round tonight. This activity will continue on
Sunday before high pressure affords a small break in the
activity on Monday and Tuesday.

&&

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

- The front returns north today, bringing a risk of heavy rain
  and flooding at least to areas south and west of Pittsburgh.
---------------------------------------------------------------

The morning will feature a good bit of lingering stratus and fog
across the area. This will likely impact some travel this
morning but the overall condition should be mostly stratus. This
will pose a hazard for the ridges, but likely not the lower
elevations. Some valley fog can`t be ruled out either. The low
stratus and fog will clear out by 14Z. The duration of the fog
may have an impact on early convection in WV.

Heading into the coming day, there have been timing
uncertainties with the convection expected today. Trends in the
CAMs suggest later timing for the bulk of the precipitation,
more towards the very late afternoon and evening. Model
soundings are suggesting some mid- level warm air/capping that
may inhibit convection until the shortwave arrives later in the
day. This late-day convection may arrive in the form of a
weakening MCS in Ohio, at a time when instability may be
diurnally decreasing. SPC has pulled the day 2 slight risk a bit
further west, essentially out of the forecast area, while
maintaining a marginal risk over areas north and west of MGW.
This seems reasonable, as increasing low- level flow and 20-30
knots of deep shear may support storm clusters capable of
damaging wind gusts mainly, with a lesser risk of large hail.

The flooding risk still exists as well given the likelihood of PWATs
rising above the 90th percentile once again by later
today and into tonight, with soundings supporting warm rain
processes especially in eastern Ohio. Interestingly, HREF
probabilities of greater than an inch of rain over 24 hours are
fairly suppressed through tonight, maximizing in the 30-50%
range west of the Ohio River and south of I-70. While the best
flood risk may exist to the southwest of Pittsburgh through
tomorrow night, think that these probabilities may be a bit
underdone. While storm motions will be higher, the potential for
heavy rates and an already saturated ground will keep the flood
risk elevated.

&&

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

- A more isolated flooding threat is possible Sunday with a cold
  frontal passage.
- Severe potential for Sunday, with damaging wind gusts being
  the most likely threat.
- High pressure keeping a dry Mon and Tue in place
----------------------------------------------------------------

Sunday will feature a cold frontal passage as the Michigan
surface low tracks into New England. Ensembles suggest a severe
threat perhaps as early as the late morning hours and into the
afternoon, with potential for 1000-1500 J/kg of surface-based
CAPE overlapping with 30-40 knots of deep shear, mainly from
Pittsburgh on south. This supports the day 2 marginal risk in
this area from SPC for mainly a wind threat. The flooding risk
will likely be confined to areas where east-west training may
occur ahead of the advancing front.

There is good confidence among the ensembles that strong ridging
builds over the Mississippi Valley and into the eastern CONUS next
week from Monday into Tuesday night. Along with crossing high
pressure to our north, a mainly dry pattern appears to extend
into Tuesday, with the potential for subsidence/warm air aloft
to suppress convection.

&&

.LONG TERM /WEDNESDAY THROUGH FRIDAY/...
KEY MESSAGES:

- Heat and humidity begin to increase during the middle part of
  the week.
- Shower/thunderstorm chances increase Thursday and Friday.
-------------------------------------------------------------------

The ridge continues to build into Wednesday leading to an
increase in temperatures and heat indices. NBM probabilities of
90+ highs increase to 40-70% over much of the area by
Wednesday, and then 50-80% on Thursday. Combined with high
dewpoints, heat risk is set to rise by the end of the forecast
period.

Shortwaves riding the top of the ridge may begin to suppress heights
slightly by the Thursday/Friday period.  This could lead to better
rain chances during this period. Longer-range machine learning
guidance suggests an uptick in severe storm potential as well, which
makes sense given the amount of instability/moisture that may be
available.

&&

.AVIATION /07Z SATURDAY THROUGH WEDNESDAY/...
Early morning satellite imagery and surface observations depict
a large MVFR to low VFR stratus deck near the stalled surface
boundary that is likely to persist through 14z. Localized top
down moistening and weak fog advection may allow for periods of
IFR, notably at HLG/MGW, but persistence is more likely to
prevail. Greatest uncertainty is whether VFR decks clear out
near FKL/DUJ; satellite trends suggest that will which should
allow for rapid low stratus/fog development.

Diurnal heating/mixing combined with slight lifting of the
boundary will slowly improve and eventually erode stratus decks
between 15z-23z. Approach of a shortwave may induce an isolated
shower/thunderstorm SE of Pittsburgh during the afternoon, but
probability of terminal impact is too low to mention.

Hi-res models suggest an MCS-like system may approach the region
after 00z from the western Great Lakes. Timing and its ability
to maintain are highly uncertain, but it may pose risk for
drastic visibility restrictions in heavy rain and gusty, erratic
winds.

Outlook...
Widespread MVFR/IFR restrictions are favored post-convective
system Saturday night into Sunday morning as moisture pooling
continues. The passage of a surface cold front underneath NW
flow Sunday afternoon/evening may offer additional thunderstorm
chances that feature gusty winds.

Ensemble models are confident in high pressure promoting dry
weather Monday and Tuesday, with subsidence aiding a prolonged
period of VFR.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.

&&

$$

SYNOPSIS...Shallenberger
NEAR TERM...Shallenberger/CL
SHORT TERM...Shallenberger/CL
LONG TERM...Shallenberger/CL
AVIATION...Frazier