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224
FXUS61 KPBZ 160253
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
1053 PM EDT Sun Sep 15 2024

.SYNOPSIS...
Dry weather will continue through Monday under high pressure.
Rain chances return Tuesday and continue periodically through
late week with the return of low pressure.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
-- Changed Discussion --
KEY MESSAGES:

- Dry weather continues through tonight under high pressure.
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Update...
Made minor adjustments mainly to the hourly temperatures, based
on the latest surface observations.

Previous discussion...
The slow, northward migration of a coastal low toward the
Carolinas will introduce thicker cirrus for eastern zones and
maintain the surface pressure gradient. The increasing cloud
cover plus enough boundary layer mixing should keep area
temperature elevated (notably along the western slopes of the
Laurel Highlands), which translates to about 5 degrees above the
daily average.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
KEY MESSAGES:

- Dry and warm again Monday.
- Low pressure may bring rain chances to the West Virginia
  ridges late Monday night.
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High pressure will remain centered across the northeastern CONUS
to start off Monday, but gradually begins to weaken and shift
east over the northern Atlantic by Monday night as a low
pressure system approaches the area from the south.

Models have maintained their recent westward trend with the
track of the low, indicating it approaches the Lower Ohio
Valley region by Tuesday. Rain chances could begin to increase
from S-N as early as Monday night as moisture and ascent
increase on the northern periphery of the approaching low.
Maintained chance POPs over the WV ridges after Midnight to
reflect this growing potential. Rain chances will increase
further going into Tuesday; more details on that can be found
in the Long Term section below.

Temperatures will be a bit cooler Monday afternoon due to the
breakdown of high pressure and increasing cloud cover, with
highs topping out in the upper 70s to low 80s. Low temperatures
Monday night actually trend a couple degrees warmer than recent
nights due to the increasing moisture and cloud cover, with
most remaining in the upper 50s.

&&

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

- Rain chances return to the region, peaking Wednesday
- Slightly above average temperature will remain before rising
  farther above normal heading into the following weekend
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Global model ensembles are favoring the trend of the coast low
aiding the development of a weak 500mb low near the Upper Ohio
River Valley Tuesday through Thursday. Return flow around this
upper feature and farther NW movement of the surface low will
aid in higher rain probabilities while excessive cloud cover
limits diurnal heating/cooling. Fine scale features remain
harder to diagnose to pinpoint potential moderate rain bands,
overall thunderstorm threat (left slight chance mention but mean
CAPE values struggle to reach 500 J/kg any afternoon), and
potential influence of the prior dry airmass on limiting
accumulations.

Confidence is fairly high on this upper wave/surface low combo
to slowly drift back toward the east coast starting Thursday.
Subsidence in its wake will cause a west to east gradient of
lower rain chances and thinning cloud cover. Increased
insolation and weak height rises should also foster slight
temperature rises through Friday. Longer range outlooks depend
on whether this wave phases with a stronger Nova Scotia trough
to maintain a positively tilted trough (resulting in slightly
cooler temperature and low probability high terrain rain) or
some sort of Great Lakes ridge building (resulting in dry
weather and above normal temperature).

&&

.AVIATION /03Z MONDAY THROUGH FRIDAY/...
VFR conditions are expected throughout the TAF period. High
clouds increase in coverage from south to north late tonight
into Monday as high pressure over the region begins to break
down and a low pressure system approaches the area from the
south.

Easterly winds could see a slight uptick Monday afternoon as
the surface pressure gradient begins to tighten ahead of the
approaching low, with guidance suggesting a more widespread
prevailing speed around 10 knots. However, cooler temperatures
and cloud cover may limit the depth of mixing and therefore gust
potential, with guidance suggesting <30% probabilities for wind
gusts exceeding 20 mph.

.Outlook...
VFR is expected through Monday. Occasional restrictions and
showers are possible Tuesday through Thursday as low pressure
slowly tracks from the Carolina coast to the Ohio Valley region.

&&

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

&&

$$

SYNOPSIS...Cermak
NEAR TERM...WM/Frazier
SHORT TERM...Cermak
LONG TERM...Frazier
AVIATION...Cermak/WM/Milcarek