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724
FXUS61 KPBZ 040758
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
358 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.

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

- Scattered showers and thunderstorms are possible today,
  favoring locations along and south of I-70. These storms may
  pose a localized flash flooding and strong wind threat.
- Should not be a washout for your Independence Day plans, but
  remain weather-aware.

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Broad surface high pressure parked over the southeast and upper
ridging across the East Coast keep warm and humid conditions in
the forecast today. Surface analysis shows a relatively warm and
muggy morning underway, with many area temperatures in the
mid-70s at 3 AM, and dewpoints sitting near 70F. With high
humidity and overcast skies, temperatures will only drop another
few degrees by sunrise. Save for patchy morning fog, a
relatively quiet morning is in store.

Isolated to scattered showers and thunderstorms are expected
again today as another weak shortwave crosses the area. After a
few isolated morning showers, better chances for rain will be
this afternoon and evening, with focus for activity mostly along
and south of a stationary boundary lying along the I-70
corridor. For those of us north of I-70, this will mean mainly
dry conditions save for a few stray showers and thunderstorms
today. Those south of I-70 will see increasing coverage this
afternoon and evening, but will still remain scattered to
isolated, and shouldn`t be a full afternoon washout.

South of I-70, 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.

With persistent cloud cover through much of the day, high
temperatures will end up nearer to seasonal norms and about 5
degrees cooler than what we saw Wednesday.

Increasing coverage of showers and thunderstorms areawide is
expected later tonight ahead of the approaching trough, but
this should be after [most] firework shows are over (we all have
that one neighbor...).

Have outdoor holiday plans? We recommend checking in on the radar
and forecast every now and then this afternoon in case rain is
moving your way.
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&&

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

- More widespread coverage is expected Friday, with damaging
  wind and flash flood threats remaining possible.
- Dry and more seasonable weather returns on Saturday.

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By Friday, a more organized shortwave and surface low pressure
crossing the Great Lakes will lift the stationary boundary
northward as a warm front, eventually pushing a late-day cold
front through the region. Increases in storm motion and lack of
parallel boundary flow should temper flash flooding risks.
However, the environment will remain similar to today, but with
convective coverage expanding to most of the forecast region.

The afternoon/evening timeframe remains the most likely period
of impact of hazardous weather (primarily damaging wind). Cloud
cover and limited insolation/surface destabilization is likely
to again be the limiting factor for severe weather, but guidance
indicates a more favorable thermodynamic profile for severe
weather Friday versus today. More robust breakup of late
morning/early afternoon cloud cover than is currently forecast is
likely to mean more robust convective development in the
afternoon.

Passage of the surface cold front and upper shortwave will
diminish storm chances Friday night, with dry and seasonable
weather returning on Saturday.
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&&

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

- High probability for dry weather and slightly above average
  temperature the rest of the weekend.
- Unsettled weather returns Tuesday through at least mid-week.

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Confidence remains high in dry weather continuing through the
weekend as surface ridging remains over the Ohio Valley and
upper troughing persists over the Central Plains. Temperatures
should remain near-normal on Sunday, but increasing return flow
and warm advection on Monday ahead of the next low pressure
system will drive daily highs back above-normal. Ensembles
indicate more active weather Tuesday into mid-week as low
pressure crosses and upper troughing sets up across the East.
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&&

.AVIATION /07Z THURSDAY THROUGH MONDAY/...
With convection over the last 6 hours, there were some
terminals from PIT and south that received substantial rainfall
and will likely assist in some MVFR/IFR cigs through dawn. While
mid level cloud cover will likely keep from any fog developing,
some cigs should be watched. These cigs will be slow to lift
through the mid morning hours and as the case for the southern
terminals, where the trough will layout, the lower layer will
become a cu layer for thunderstorm development but mainly in the
late afternoon and evening. Expect this convection to weaken
after 00Z. Winds will be light and variable through the period
with the exception of thunderstorms.

.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
SHORT TERM...Rackley
LONG TERM...Rackley/Frazier
AVIATION...Kramar/Shallenberger