643
FXUS61 KPBZ 040454
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
1254 AM EDT Thu Jul 4 2024

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

&&

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

- Isolated showers are expected through the overnight period.
- Scattered showers and thunderstorms are likely Thursday,
  favoring locations along and south of I-70. These storms may
  pose a localized flash flood threat.

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A broken line of showers continues to dissipate as it crosses
southern portions of the area and outruns remaining instability.
A few isolated showers and perhaps a rumble of thunder may
continue overnight, favoring locations south of I-70. Otherwise,
mostly cloudy skies are expected with patchy fog possible,
especially across the PHD-ZZV area where thunderstorms occurred.
Warm low temperatures approximately 10 degrees above average are
expected.

Broad west-southwest flow and a series of shortwaves amid a
warm/humid environment will keep periodic showers and
thunderstorms in the forecast today and Friday. Focus for
activity will be along a stationary boundary lying along the
I-70 corridor, with most convection occuring south of this
boundary and a gradient of decreasing probabilities to the
north.

The good news for outdoor holiday activities is
afternoon/evening coverage for storms, even south of the
boundary, looks to remain isolated to scattered. Morning
coverage looks low for most locations, with perhaps a stray
shower or two popping up across the area.

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. Any flooding or severe wind threat will be maximized
in the afternoon/evening period when surface-based instability
will be maximized. These threats will trend down through the
evening and overnight.

&&

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

- More widespread coverage is expected Friday, with damaging
  wind and flash flood threats remaining possible.

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By 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 /04Z 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...Rackley/Frazier
SHORT TERM...Frazier
LONG TERM...Frazier
AVIATION...Cermak/Kramar/Rackley