226
FXUS61 KPBZ 300540
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
140 AM EDT Mon Sep 30 2024

.SYNOPSIS...
An upper level low will drift northeastward from Kentucky to the
Atlantic coast through Tuesday, keeping unsettled weather and
near to just above normal temperatures. A frontal passage by
Wednesday will bring drier weather and seasonable temperatures
to close out the week.

&&

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

- Mostly light rain continues tonight and into the day tomorrow,
  primarily south of Pittsburgh.
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The low aloft will continue to meander across the Ohio Valley
through dawn and into the coming day. The best PoPs through dawn
will be near and south of Pittsburgh as the best convergence
shifts to this region. The abundant cloud cover will help keep
diurnal ranges small, with lows some 10 to 15 degrees above
climatology.

The upper low starts to make some eastward progress on Monday as an
upstream shortwave trough over the northern Plains starts to nudge a
Great Lakes ridge axis eastward, causing the upper low to start to
eject. PoPs will show a north-to-south positive gradient into Monday
night, following the pattern of best moisture and low-level
convergence. Instability gets shunted south of the region per the
HREF, and thus thunder is less likely. The lack of convection will
create a more uniform QPF pattern. Chances of exceeding 0.25" over
the Monday/Monday night period are maximized at 60-70% along the
southeast ridges.

&&

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

- Continued rain chances with seasonably warm lows and
  seasonable highs.
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The Tuesday/Tuesday night period will be a transition period.  The
upper low will slowly degrade as it lifts to the northeast,
eventually reaching the Atlantic Coast by 00Z Wednesday as an open
trough.  Meanwhile, the northern stream shortwave will be crossing
the Great Lakes, pushing a cold front in our direction.  The most
likely time for FROPA appears to be Tuesday night, with a slight
delay into Wednesday possible. Showers are most likely Tuesday to
the southeast of Pittsburgh in the path of the upper low, but cannot
be totally ruled out anywhere.  Much of the region can expect a
mostly cloudy sky for a good portion of the day though. PoPs Tuesday
night with the front will be highest north of Pittsburgh, with left
exit region jet dynamics potentially playing a role. Fast movement
overall should keep rain totals in check.

With a few cloud breaks possible, and with the departure of the
upper low, Tuesday highs may tick up a couple degrees as compared to
Monday, with lower but still warmer-than-normal lows at night with
the frontal passage. The cold front will complete its passage on
Wednesday if it has not already done so by Tuesday night. This
will usher in some drier and cooler air as temperatures will be
near or just below normal for Wednesday. Dry conditions are
expected as well.

&&

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

- A cold front passage is expected by early Wednesday, bringing
  an end to rain chances.
- An overall drier and less cloudy pattern is expected into next
  weekend.
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Expect a more quasi- zonal flow pattern takes hold through next
weekend. Overall, this appears to be a fairly dry period as
access to southern moisture remains mostly cut off. Still, some
model solutions suggest that a weak front may provide isolated
showers around Friday night.

Temperatures are showing more uncertainty, as 500mb heights over our
region will ultimately depends on upstream developments over the
western CONUS.  Model clusters are showing various ridge/trough
scenarios that could cause highs/lows to stray a bit further from
climatology than the current forecast.  However, given the overall
zonal pattern and until a more clear signal emerges, will keep
temperatures not too far from normal values overall.

&&

.AVIATION /05Z MONDAY THROUGH FRIDAY/...
Low confidence forecast on placement of IFR/MVFR ceiling
heights through the TAF period. Low pressure continues to spin
across the Tennessee Valley region. Waves of light rain
rotating around the low will continue to affect airports across
the Upper Ohio Valley region through the TAF period. A wide
range in cig heights were observed this afternoon and evening,
with VFR to LIFR. Airports along and north of an HLG-PIT-LBE
have been mainly IFR, with VFR to the south.

Would expect conditions to deteriorate to IFR for most airports
tonight with low level moisture in place, and additional light
rainfall. Probabilistic guidance indicates a relatively low
probability of this occuring, with deterministic guidance siding
toward the IFR solution. Will maintain the restricted cigs
overnight in the TAF, with some improvement later Monday as
the low begins to shift eastward.

.Outlook...
Restrictions are possible through Tuesday as the upper low
continues to drift eastward, and a cold front crosses the region
late Tuesday. High pressure then returns VFR to the region
through Friday.

&&

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

&&

$$

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