389
FXUS61 KPBZ 070601
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
201 AM EDT Tue May 7 2024

.SYNOPSIS...
Muggy conditions continue early this morning with patchy fog in
some locations. Severe weather potential increases Tuesday
evening after 6pm, and could last into the overnight hours.
Another round of severe weather could potentially impact
southern portions of the area early Thursday morning. Cooler
weather is expected this weekend.

&&

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

- Fog will be possible late tonight in the wake of afternoon
  showers and storms, especially south of Pittsburgh

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Lingering showers across southern zones have mostly come to an
end early this morning. Lingering boundary layer moisture is
evident from surface analysis as a sharp dew point gradient
across the area. North of Pittsburgh, dews ranging from 35-50F
can be seen, with values in the 60s south of Pittsburgh. Fog is
likely (45-65%) for areas south of I-70 through sunrise, with
dense fog (<1/4) probabilities around 40-50%. Will continue to
monitor the need for a Dense Fog Advisory. The overnight period
remains quiet otherwise...

Ridging will briefly build over the Great Lakes and Ohio Valley
today as a large low pressure system lifts across the Dakotas.
This will keep the area mostly dry in the morning/early
afternoon. A few stray showers may develop after 3pm as the
ridge axis quickly breaks down and a new surface low develops
along a warm front in the Midwest.



&&

.SHORT TERM /THIS EVENING THROUGH WEDNESDAY/...
KEY MESSAGES:

- Severe storms are possible late this evening into early
  Wednesday morning.
- Hail, damaging wind, tornadoes, and flooding are possible with
  these storms.
- Highest probability for severe weather is across eastern Ohio.
- Ridging over the Great Lakes is expected to reduce
  precipitation chances briefly Wednesday afternoon/evening

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Ongoing convection from storms currently across the Plains will
shift eastward across the Mississippi Valley this morning,
strengthening to our west across the Ohio Valley with diurnal
heating and an increasingly unstable atmosphere this afternoon.
These storms will reach eastern Ohio near sunset. Despite the
loss of surface heating, a surge of warm/moist air amidst a
crossing low level jet may keep the region modestly unstable
into the overnight. This will be the key factor in how far east
severe storms persist, as shear will be more than sufficient to
maintain well-organized storms (Bulk Shear ~50 kts).

Modeled soundings across Ohio support a clustered or
discrete/supercell environment during the afternoon. These cells
will be capable of producing large hail, damaging winds, and
tornadoes before eventually weakening somewhere across our
forecast area. The potential for severe storms rapidly decreases
after 2am Wednesday morning as mid-level ridging builds.

A brief respite from rainfall is expected during the day on
Wednesday with high pressure in place behind the front.
Temperatures will push back into the upper 70s and lower 80s for
much of the area with plentiful sunshine.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
KEY MESSAGES:

- A new disturbance is expected to produce severe storms early
  Thu morning
- Model ensembles suggest a very wet pattern into the weekend
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A new low pressure system will form over the Great Plains early
Wed, track east, and enter the Ohio River Valley early Thu
morning. Another round of severe storms could produce damaging
wind, and/or tornadoes due to high shear and MUCAPE of 500-1200
J/kg. The low-level jet will likely be stronger than the Tue
night disturbance. Hi-Res guidance suggests 850mb wind of 55-65
kt could be present.

A passing cold front may stir additional severe storms Thu
afternoon southeast of Pittsburgh. However, the main threat will
likely reside over the eastern CONUS (noted in SPC`s Day 4
Outlook).


Model ensembles project a pattern shift late week as an
elongated trough builds over the Great Lakes. Below-average
temperature is likely Fri through Sun within northwesterly
flow, and 850mb temperature could range from 2C to -1C. At the
moment, the potential for frost/freeze concerns is considered
low.

&&

.AVIATION /05Z TUESDAY THROUGH SATURDAY/...
High pressure centered north of Lake Erie will continue to
promote VFR conditions for mainly FKL and DUJ. Further to the
southern terminals, the encroachment of a warm front well south
of the region will nudge MVFR to localized IFR cigs to southern
terminals, most notably, MGW through dawn. The rest of the
terminals will likely deal with MVFR conditions through dawn due
to the moisture advection and stagnant conditions.
Additionally, diurnal heating is expected to promote bkn VFR cu
through the afternoon (with a brief window of MVFR with cu
initialization).

Showers and thunderstorms will increase in probability Tuesday
afternoon and evening. The first line along a pre- frontal
trough should dissipate/decay before reaching much of eastern OH
between 21z-00z. The higher confidence line should move through
the region between 02z-08z; be prepared for gusty wind and cloud
to ground lightning with that convection.

.Outlook...
The active weather pattern will persist through the end of the
week by promoting periods of showers and thunderstorms.

&&

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

&&

$$

SYNOPSIS...Rackley
NEAR TERM...Rackley
SHORT TERM...Rackley/Hefferan
LONG TERM...Hefferan
AVIATION...Frazier/Shallenberger