157
FXUS61 KPBZ 150722 CCA
AFDPBZ

Area Forecast Discussion...CORRECTED
National Weather Service Pittsburgh PA
322 AM EDT Wed May 15 2024

.SYNOPSIS...
Isolated to scattered showers expected today as an upper trough
crosses the region. A few rumbles of thunders will be possible
during the afternoon north and west of Pittsburgh. Showers and
storms will be possible again Friday and Saturday after a dry
Thursday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
KEY MESSAGES:

- Isolated to scattered light showers possible.
- Thunderstorm chances remain low, with no severe threat.
- Near-normal temperatures.
  ______________________________________________________________

Upper troughing over the Middle Ohio Valley will slowly
transition east over the course of the day as a surface low
passes south of the Mason-Dixon line. This will support isolated
to scattered showers today across the region with better
coverage north and west of PGH, where a slow-approaching
surface boundary. Any thunder should largely also be north and
east of PGH. NBM 6hr prob thunder tops out at 40% and the HREF
10th-90th percentile CAPE spread ranges from double digits to
near 800J/kg. Latest shear profiles do not promote and
organization. Total precipitation amounts will range from a few
hundredths east of PGH up to 0.4-0.5" over eastern Ohio
counties.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...
KEY MESSAGES:

- Ridging provides drier weather tonight through Thursday.
- Near to above normal temperature expected.
  ______________________________________________________________

Precipitation coverage should wane this evening as the trough
axis shifts east of the region and heights rise aloft. With
ridging the dominant feature, warmer temperatures and dry
conditions are then forecast through Thursday night, although
some showers may begin to show up in the western CWA prior to
12Z Friday ahead of the next shortwave.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
KEY MESSAGES:

- Forecast uncertainty increases during the extended period.
- Another trough is likely to provide unsettled weather at least
  for Friday and Saturday, although rain amounts are iffy given
  the uncertainty.
- Temperatures near or above normal are expected.
  ______________________________________________________________

Uncertainty creeps upward in the extended period.  The mid-level
ridge will be departing the Appalachians Friday morning, with
moisture increasing once again ahead of the next trough, which
ensembles have crossing the Mississippi River Friday evening and
reaching the Upper Ohio Valley by Saturday.

Thereafter, speed and timing differences arise in the models with
the handling of this trough. GEFS/GEPS members are favoring a
quicker departure and a weaker trough, while ENS favors the opposite
outcomes. Differences then continue to get larger from there, with
cluster analysis indicating anything from strong ridging to the
presence of a closed upper low is on the table by early next week.

A good example is looking at NBM 10th/90th 72hr QPF percentiles
for the weekend....ranging from 0.04" to 1.38" for the
Pittsburgh metro area.

Will continue to roll with the NBM suggestions for the extended
period and wait for increased model clarity. This would suggest
a return of unsettled, but likely not overly impactful weather
Friday and Saturday, with lower rain chances during the early
part of next week. Near to slightly above normal temperatures
are currently forecast, but again, there is a sizable range of
outcomes here.

&&

.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
Low pressure near the OH/KY border (with an inverted surface
trough extending north) will continue to drift eastward today,
eventually weakening into a trough as a new surface low develops
off the Mid Atlantic coast. Initially, showers and thunderstorms
will affect ZZV early in the TAF period as a wave of ascent and
enhanced moisture rotates around the low. Otherwise, MVFR should
become widespread overnight as cigs lower with increasing low
level moisture around the low. The exception will be FKL and DUJ,
where moist easterly flow should maintain IFR cigs.

Scattered showers and MVFR cigs (IFR at FKL/DUJ) will continue
today as the low moves eastward. Some improvement to low VFR is
expected through the afternoon with surface heating and mixing.
The greatest amount of destabilization is expected near the
inverted surface trough, which is expected to be near DUJ-FKL-
ZZV this afternoon. A band of MU CAPE around 500 j/kg is depicted
on the latest HREF output in this vicinity. Maintained a prob30
for thunderstorms for those ports affected, with showers
mentioned just to the east of this boundary where less
instability is progged.

Cigs should lower to MVFR again Wednesday evening as the trough
dissipates across the Upper Ohio Valley region, but low level
moisture remains.

.Outlook...
VFR should return Thursday under a ridge of high pressure.
Periodic restrictions and showers are expected Friday through
Sunday with another slow moving low pressure system.


&&

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

&&

$$

SYNOPSIS...88
NEAR TERM...88
SHORT TERM...88
LONG TERM...CL/88
AVIATION...WM