986
FXUS61 KPBZ 071732
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
132 PM EDT Tue May 7 2024

.SYNOPSIS...
Severe weather potential will increase this evening and last
into the overnight hours. Another round of severe weather could
potentially impact southern portions of the region early
Thursday morning. Cooler weather is expected this weekend.

&&

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

- Severe storms are possible late this evening into early
  Wednesday morning.
- Probabilities for severe weather area highest for our CWA
  across east-central Ohio.
- All modes of severe weather (large hail, damaging wind,
  tornadoes, and flooding) are possible with these storms.

-------------------------------------------------------------------

Ridging will briefly build over the Great Lakes and Ohio
Valley today as a large low pressure system lifts and occludes
across the Dakotas. This afternoon, a stationary front to our
south will lift north across the region as a warm front. This
will allow a few stray showers and non-severe storms to develop
across portions of southwest PA and northern WV.

Ongoing convection from storms currently across the Plains will
shift eastward across the Mississippi Valley through this
morning, strengthening to our west across the Ohio Valley with
diurnal heating and an increasingly unstable atmosphere this
afternoon. CAMs show an initial round of thunderstorms rapidly
decaying across central Ohio by mid-afternoon as it outruns
better dynamic/thermodynamic support to the west.

A second round of more potent thunderstorms is expected to
develop behind this initial feature, coincident with a crossing
shortwave and strengthening low-level jet. These storms will
reach eastern Ohio near sunset. Despite the loss of surface
heating, a surge of warm/moist air may keep the region modestly
unstable into the overnight. This will be a key factor in how
far east severe storms can persist, as ample 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. Probabilities for severe weather remain highest
in our area across east-central Ohio where SPC has highlighted a
Slight Risk (2/5). Farther east, a Marginal Risk (1/5) flags
the lower-end threat. The potential for severe storms rapidly
decreases after 2am Wednesday morning as mid-level ridging
builds.

Though quick storm motion should preclude widespread flooding
risk, high PWAT (~1.5") will allow for heavy rainfall rates and
the potential for localized flash flooding.

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
KEY MESSAGES:

- Brief ridging will allow for dry weather with sunshine on
  Wednesday.
- Additional storms are possible late Wednesday night into early
  Thursday morning, but probabilities are increasing for severe
  storms to stay south of the forecast area.

-------------------------------------------------------------------

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.

Another disturbance is expected Wednesday night into early
Thursday morning as another low pressure system develops over
the Plains and crosses into the Ohio Valley. At this time,
severe weather appears to be initially focused along a warm
front lifting north across across southern IL/IN/KY. Recent
guidance trends keep stall this boundary with much slower
northward progress. This should keep most initial convection to
our south Wednesday evening into Wednesday night. The SPC
Convective Outlook reflects this change, pulling the Slight Risk
south out of our area. Severe storms could still be possible
across northern West Virginia if this feature were to shift
farther north, but probabilities for this are decreasing.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
KEY MESSAGES:

- Ensembles suggest a wet pattern into the weekend.
- Cooler temperatures arrive by late week with highs in the 60s
  this weekend.
-------------------------------------------------------------------

Crossing low pressure will keep showers and thunderstorms in the
forecast Thursday into Friday. Deep eastern CONUS troughing
developing late week and a series of shortwaves traversing the
upper flow will then keep daily shower and thunderstorm chance
in the forecast through early next week.

Below-average temperature is likely Friday through Sunday
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 /17Z TUESDAY THROUGH SATURDAY/. before a line of
Broken high MVFR / low VFR cigs will be rule before a line of
showers and thunderstorms move through the region between
02z-08z. Gusty winds and frequent cloud to ground lightning can
be expected with convection at all ports. KZZV will have the
highest probability severe weather including hail. Timing in 18Z
TAFs were largely based off the HREF and RRFS. Ensemble guidance
gives a 80-90% probability of MVFR cigs with and following
convection and 30-40% for IFR cigs. Went optimistic with MVFR
for now, but may need amended later based off upstream
observations.

.Outlook...
Restrictions with showers and storms are likely early Thursday
through Friday with crossing low pressure.

&&

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

&&

$$

SYNOPSIS...Rackley
NEAR TERM...Rackley
SHORT TERM...Rackley
LONG TERM...Hefferan/Rackley
AVIATION...88