303
FXUS61 KPBZ 040046
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
846 PM EDT Wed Jul 3 2024

.SYNOPSIS...
A series of disturbances will create periods of scattered
thunderstorms tonight through Friday, offering low probabilities
for localized flash flooding and gusty wind. Dry weather with
seasonable temperature are expected to return Saturday into
Sunday.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
KEY MESSAGES:

- Isolated to scattered showers and possible thunderstorms
  expected through the overnight period.

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845 PM Update...

A broken line of showers and thunderstorms continues to advance
across the Upper Ohio Valley region this evening, ahead of a
shortwave trough/vorticity maximum. The latest mesoanalysis
shows most of the ML CAPE has waned across western PA, with
levels around 500 j/kg across eastern Ohio. The 00Z PIT sounding
also indicated poor mid level lapse rates, with warm
temperatures aloft. Radar continues to show the line of
showers/storms weakening and dissipating as it tracks eastward
and outruns the instability.

Isolated to scattered showers will continue overnight as the
shortwave completes its passage. A rumble of thunder will also
be possible with minimal elevated instability, though this
potential appears low. Otherwise, mostly cloudy skies are
expected overnight. Patchy fog is possible, especially across
the PHD-ZZV area, where thunderstorms occurred today. It will
be a warm night, with temperatures around 10 degrees above
average.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
KEY MESSAGES:

- Scattered to numerous showers and thunderstorms are likely
  Thursday, favoring locations along and south of I-70. These
  storms may pose a localized flash flood threat.
- More widespread coverage is expected Friday, with damaging
  wind and flash flood threats remaining possible.

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Broad west southwest flow will remain in place over the Upper
Ohio River Valley region as the main trough axis sits over the
Central Plains Thursday and Friday. A series of shortwaves will
traverse the region within this flow and tap into the warm,
humid environment to create periodic shower and thunderstorm
chances.

For Thursday, a stationary boundary laying roughly along the
I-70 corridor will serve as a focus for convective development
throughout the day; areas to the south are thus more likely to
see convection while a gradient of decreasing probabilities
exist to the north. Modest instability (around 1000 J/KG), weak
lapse rates, and weak forcing should limit concerns for damaging
wind and localized flash flooding but low probabilities remain
given near record PWAT values, enough column shear, and
potential for some storm training with parallel storm flow and
surface boundary. The afternoon to evening period, where
surface based instability is maximized, is likely when those
threats are maximized before trending down overnight.

For Friday, a more organized shortwave will lift the stationary
boundary northward as a warm front and push through a late day
cold front. Increases in storm motion and lack of parallel
boundary flow should temper flash flood risks, otherwise the
environment should resemble that of Thursday`s but for most of
the forecast region. The afternoon/evening timeframe remains the
most likely period of impact of hazardous weather.

Passage of the surface cold front and upper shortwave will
diminish storm chances Friday night and initiate a period of
drier and more seasonable weather.

&&

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

- High probability for dry weather and slightly above average
  temperature the rest of the weekend.

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Confidence remains high as ensembles show strong agreement of
dry and seasonable weather developing Saturday and Sunday. This
is a result of upper troughing persisting over the Central
Plains and the Upper Ohio River Valley within the dry slot of
southwest flow (plus surface ridging). Expect near to slightly
above average temperature Saturday and Sunday before temperature
returns well above normal Monday (think upper 80s to lower 90s)
as warm, moist advection increases ahead of the next low
pressure system set to cross Tuesday into Wednesday.

&&

.AVIATION /01Z THURSDAY THROUGH MONDAY/...
Deeper convection has remained near ZZV while updrafts to the
northeast from PHD-FKL have weakened considerably as they
encountered diminishing buoyancy. Storms will affect ZZV thru
04/0100-0200 UTC before they continue ewd into increasingly
hostile environment. Weakening showers are likely to affect HLG
thru 04/0300-0400 UTC.

In the wake of the evening convection, mid-level clouds are
anticipated, and perhaps a scattered lower deck around 4 kft. By
morning, MVFR cigs (1.5-2.5 kft) are anticipated with high
likelihood (70-80% probability) for a few hours in advance of an
approaching series of troughs, which seem poised to invigorate
showers near the srn terminals (ZZV/MGW) around sunrise. Cigs
should lift to higher MVFR/VFR by late morning, when broader
coverage of showers and storms begins in the early afternoon.
Greatest coverage appears to be focused from ZZV-LBE during the
04/1900-2300 UTC timeframe before diurnal stabilization weakens
their potential.

.Outlook...
Additional rounds of showers and thunderstorms (with occasional
restrictions) are then expected episodically through early Sat
as a cold front slowly crosses. VFR should return Sun amid high
pressure.

&&

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

&&

$$

SYNOPSIS...Frazier
NEAR TERM...WM/Frazier
SHORT TERM...Frazier
LONG TERM...Frazier
AVIATION...Cermak/Kramar/Rackley