154
FXUS61 KPBZ 261508
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
1108 AM EDT Wed Jun 26 2024

.SYNOPSIS...
Thunderstorms capable of producing damaging wind and localized
flooding are expected this afternoon and evening ahead of a cold
front. Dry and seasonable weather will return Thursday, with
rising temperature expected Friday.

&&

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

- Strong to severe storms are expected between 1pm to 8pm.
  Damaging winds will be the main threat. An isolated tornadoes
  and hail as large as a quarter can`t be ruled out.
- Storm Prediction Center (SPC) has expanded the Slight Risk for
  severe weather across the region, and Weather Prediction
  Center (WPC) has continued the Marginal risk for flooding.

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11am Update:
Weak vorticity advection from the lower Ohio River Valley will
continue to provide enough ascent within a weakly unstable
(elevated) environment to push areas of light rain and low
probability thunderstorms into southeast Ohio over the next two
hours. PoP forecast has been updated to account for this
feature; the expectation/focus remains on this afternoon with
convection firing along/near Lake Erie and moving SE. The lower
OH movement isn`t expected to disrupt storm evolution off the
lakes, but that isn`t 100 percent confident. The rest of the
daytime scenario is discussed below.

Rest of the Discussion...
An well-organized upper shortwave trough is expected to drop
southeast from the western Great Lakes today and cross the Upper
Ohio River Valley region through tonight, pushing through a
surface cold front. Ahead of this feature, moist advection is
helping to create a storm environment featuring above 90th
percentile PWAT values, 30-40kts of effective shear, and between
1000-2000 J/kb SBCAPE (the latter two increasing towards those
values by the afternoon). The resulting chemistry of the large-
scale synoptic pattern and meso setup should feature fairly
widespread thunderstorm development initiatilizing near the cold
front along Lake Erie and traversing ESE between 1pm to 10pm
EDT. Environment and model-supported outlooks favor a damaging
wind and localized flooding threat for the stronger, more
organized thunderstorms (that will attempt to be more line/QLCS
oriented); however, lower probabilities still exist for large
hail (due to for deep updrafts) and a tornado (lower LCL heights
and modest sfc-1km shear).

Shower and thunderstorm activity is likely to weaken late
tonight as surface instability wanes along with the passage of
the cold front. Much of the severe threat should subside by 10pm
EDT while lingering post-frontal showers and convective
stratiform rain regions exit the higher terrain of WV by early
Thursday morning. Dry air and residual mixing of a NW post-
frontal wind should mitigate morning fog risk, but residual
boundary layer moisture in river valleys (favoring locations SE
of Pittsburgh) could have patchy fog development.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
KEY MESSAGES:

- Dry weather returns.
- Temperatures increase Friday into the weekend.

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Dry conditions resume Thursday as high pressure builds in
across the region. A warming trend in temperatures is
forecasted Friday and into the weekend as h500 heights approach
890dm. This combined with increasing low-level moisture will
result in apparent temperatures back up in the mid 90s by the
weekend.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
KEY MESSAGES:

- Shower and thunderstorm chances return Saturday into Sunday
  with the next low pressure system.

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Ensembles show about a 50% chance in general of highs hitting
90F on Saturday. There`s a good chance most locations will see
apparent temperatures back in the 90s with Tds back up in the
upper 60s / low 70s.

Shower and thunderstorm chances return with increased
instability and the approach and passage of another frontal
system Saturday into Sunday.

Dry conditions and near to slightly above normal temperatures
are forecast early next week as high pressure resumes control.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
VFR is expected through the morning ahead of an approaching
shortwave trough and associated surface cold front. Mid and high
level clouds will continue to stream across the area ahead of
the wave. Expect a scattered cumulus layer to develop by late
morning/early afternoon with a flux of low-level moisture and
diurnal heating.

Pre-frontal showers and storms will increase in coverage from
west to east after 17Z. However, it appears the most favorable
timing for thunderstorms to impact terminals will be between
20Z and 00Z; TEMPO groups have been included with this morning
update. Strong wind gusts and hail are possible in these
storms, and additional details can be added to the tafs as
uncertainty decreases later in the day.

MVFR is expected as the thunderstorms end, with a period of
showers. Eventual IFR is possible overnight with low level
moisture in place.

.Outlook...
Restrictions in stratus/fog are possible through early Thursday;
especially between 06Z to 12Z.

VFR is then expected through Friday under high pressure.

Restriction and showers/thunderstorm potential returns Friday
night with a crossing warm front. Restrictions are expected at
times Saturday and Saturday night with showers and thunderstorms
ahead of and along a crossing cold front. VFR returns Sunday
under high pressure.

&&

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

&&

$$

SYNOPSIS...Frazier
NEAR TERM...Frazier
SHORT TERM...88
LONG TERM...88
AVIATION...WM