972
FXUS61 KPBZ 250105 AAA
AFDPBZ

Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
905 PM EDT Tue Sep 24 2024

.SYNOPSIS...
Scattered showers and a few thunderstorms will move across the
area at times through Wednesday, ahead of a slow moving cold
front. Rain chances return Friday into the weekend with low
pressure.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
KEY MESSAGES:

- Scattered showers and possible thunderstorms tonight

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The latest surface analysis shows surface low pressure across
Michigan, with a warm front extending through NW PA. A cold
front extends south from the low. The latest mesoanalysis shows
ML CAPE decreasing over the past few hours, with a diminishing
trend in the 0-6km shear as well.

A shortwave trough/upper low remains across the Midwest.
Individual shortwaves embedded in SW flow ahead of the trough
will maintain isolated to scattered showers at times overnight
as they track across the Upper Ohio Valley region. With the
waning instability and shear, the severe weather potential
diminished. The potential for thunder will continue mainly west
and south of PIT early this evening, before that also ends.

Similar to recent nights, temperatures will average around 10
degrees above seasonable levels with cloud cover in place.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY/...
KEY MESSAGES:

- Rain chances continue through mid-week.

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Showers and weak thunderstorms will likely be ongoing early
Wednesday morning as a trough continues to move across the Ohio
River Valley. The potential of strong storms will be considered
low given weak instability and the absence of a lifting
mechanism.

By 8am Wednesday, the cold front will likely be positioned in
western Ohio and stall due to the mean flow orientated parallel
to the boundary. Showers and storms may redevelop in eastern
Ohio along the stalled frontal boundary and along any
moisture/temperature gradient boundaries that develop after
12pm.

Shower and storm potential is expected to decrease after 10pm
with the loss of surface heating.

Above average temperatures are expected through this time period
under deep southerly flow.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
KEY MESSAGES:

- Uncertainty increases greatly for the end of the week with
  Tropical Storm Helene.
- Rain chances will continue through the end of the week.
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The central CONUS trough may interact with Tropical Storm Helene as
it moves inland out of the Gulf. Meanwhile, the northern stream
trough will be sliding across the Northeast states. Ensemble
clusters all show that the remnants will be absorbed by the
trough but with much uncertainty after that.

The highest probability scenario at this time is that the northern
stream trough deflects the remnants off to our west and rain chances
stay low.

There are potentially wetter solutions with a track further
east; one of the members depicts 2-3 inches of rain with this
outcome. However, there is a 10% chance of exceeding 2 inches of
rain in 24 hours with 13Z NBM run. If impacts do evolve from
Helene, it would likely be Friday into Saturday.

By Monday into Tuesday, the remnants of an upper-level low
associated with Helene will weaken near our southwest of the
Ohio River Valley and drift east as a trough over the Dakotas
ejects southeast.

&&

.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
Scattered showers will continue to cross the area through the
evening and into the early overnight. Some minor instances of
restrictions are possible through the evening.

Deteriorating conditions are expected late tonight into
Wednesday morning with ensemble guidance suggesting a greater
than 70% chance of MVFR cigs (30-50% chance of IFR) at all
terminals by or shortly after sunrise. Additionally, any
locations that saw heavy rain today will likely see some amount
of fog development overnight, further impacting flight
categories at area airports through sunrise.

Another round of showers and thunderstorms are expected through
dawn and through midday. This will impact cigs through the
coming day as well. Expect intermittent restrictions through
the day tomorrow with passing thunderstorms.

.Outlook...
Some improvement is expected Wednesday, with a 80% chance of
VFR everywhere except FKL/DUJ, though very isolated showers and
storms may bring temporary cig/vis drops. Widespread restriction
chances increase again Thursday morning, before VFR returns to
close out the work week.

&&

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

&&

$$

SYNOPSIS...WM
NEAR TERM...WM
SHORT TERM...Hefferan
LONG TERM...Hefferan
AVIATION...Cermak/Shallenberger