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994
FXUS61 KPBZ 230026
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
826 PM EDT Wed May 22 2024

.SYNOPSIS...
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Showers and thunderstorms are possible overnight and into
Thursday as temperature remains seasonably warm. Periodic
thunderstorm chances are expected through the holiday weekend as
a series of upper level disturbances cross the region.
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&&

.NEAR TERM /UNTIL 8 AM THURSDAY MORNING/...
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KEY MESSAGES:

- Strong to severe thunderstorms possible tonight into Thursday
  morning.
- Damaging wind is the primary threat.
  _____________________________________________________________

8:45pm Update:

To the west, the cold front continues to advance eastward as
finallythe forcing associated with the front has allowed to
break the cap and continue ascent. Expect shear associated with
the front to allow some convection to continue to develop east
but slowly weaken with time as the environment to the east is
also capped and only experience a few cells through the
afternoon. Especially heading into the overnight hours and the
loss of additional heating, expect inhibition to increase. Thus,
convection will continue to be dependent on the arrival of the4
front. If trends suggest the current track, the storms should
get ahead of the front and begin to weaken as they track east
out ahead of the front, lowering the severe potential for the
forecast area.

With the fronts arrival later tonight, there is the chance of
the boundary oriented with the the flow and could lead to a
flooding situation later tonight. Thus, flooding remains a
threat in any training storms. Additionally, the front may slow
its progression overnight as it drags across the area, which
will warrant continued watching.
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&&

.SHORT TERM /8 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
KEY MESSAGES:


- Showers and thunderstorms are likely to continue ahead of a
  cold front Thursday.
  _____________________________________________________________

The surface cold front will stall just north of the I-70
corridor Thursday morning as the upper level trough lifts
farther north of the region and broader SW flow develops aloft.
Diurnal heating combined with weak embedded waves is expected to
foster isolated to scattered thunderstorms south of the boundary
through the day. The lack of strong heating and weak shear
should preclude severe potential while flooding likely will
remain limited due to storm motion (though non-zero as flow will
be nearly parallel to the boundary and could foster some
training).

Confidence is high that dry weather will develop Thursday night
into Friday as shortwave ridging crosses the region with high
pressure at the surface. Minimal airmass change with slightly
higher heights should promote above normal temperature again.
The aspect to keep an eye on is progression of lower Ohio River
Valley convection eastward; there remains potential for a late
Friday into Saturday morning arrival (with limited severe
potential as it would hit a more stable environment).

&&

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

- Variability remains high on long term forecast and may be
  predicated on prior day`s convective outcomes.
- Overall, periodic showers and thunderstorms with slightly
  above normal temperature is favored through the holiday
  weekend.
  ____________________________________________________________

Ensembles are more confident in one of those waves crossing the
region Saturday to produced a wave of showers and
thunderstorms; timing varies but potential exists for convection
to exit east of the area before evening activities. That
variability leads to an inconclusiveness on severe potential but
note that analogs for the pattern and machine-learning analysis
suggests at least a low probability for hazardous weather that
day.

A more well-organized low pressure system is becoming the
favored pattern development to end the holiday weekend as it
lifts through the Great Lakes. Higher probabilities for showers
and thunderstorms are expected during this time frame but it is
unlikely to be "all day" rain type of events. Early analogs for
this pattern also suggest at least a low probability for
hazardous weather, but much variation in that potential remains.

Long range suggests a shift to a cooler, dry pattern by the
middle of next week as upper troughing develops over the Great
Lakes. Expect temperature to fall below the seasonal average,
with Tuesday potentially being the transition day from shower
activity to dry weather.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
A rapid decrease of showers and storms, even cloud coverage,
has taken hold this evening in the wake of departing convection
as localized subsidence has developed and impinging dry air
aloft has put a cap on things. Expecting that this will continue
to be the trend through the evening, though can`t entirely rule
out a thunderstorm developing, but confidence is low given the
lack of an initiating mechanism. For this reason, have removed
thunder and precip chances at all sites until after 00z when
a cold front will approach the area and is expected to then
initiate more showers and thunderstorms, some of which may still
be capable of gusty wind and hail.

Outside of thunderstorms, there is high confidence that VFR
prevails aside from MGW/LBE which have the highest probability
of MVFR CIG and VIS after 08z with increasing low level moisture
and light rain showers continuing. Low probabilities for MVFR
CIGs creep as far north as PIT, but profiles suggest it`s likely
too dry for restrictions. It`s most likely that MVFR CIGs
continue for MGW/LBE until 15z or so when mixing erodes the
cloud deck and returns VFR. Additional showers and thunderstorms
are expected to develop Thursday afternoon primarily south of
PIT which may return associated chances for restrictions in the
afternoon.

.Outlook...
Periodic thunderstorm chances and restrictions are likely
through the weekend as an active weather pattern continues.

&&

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

&&

$$

SYNOPSIS...Shallenberger
NEAR TERM...Frazier/Milcarek/Shallenberger
SHORT TERM...Frazier
LONG TERM...Frazier
AVIATION...MLB