048
FXUS61 KPBZ 241747
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
147 PM EDT Sat May 24 2025

.SYNOPSIS...
Progressively drier and warmer conditions are forecast through
Memorial Day. Rain chances increase Tuesday with more seasonable
temperatures favored for the rest of the week.

&&

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

- Temperatures remain seasonably cool with shower potential
lingering in northwest PA for the daytime.
- Some frost potential overnight. Frost Advisory for Eastern Tucker
County from 1am to 9am on Sunday.
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Based on satellite observations, a generally thick low cloud deck is
located northeast of Pittsburgh associated with the showers, which
is favored to linger for the remainder of today. Shallow instability
plus the northwesterly flow will maintain that chance of showers,
but elsewhere, limited moisture depth makes shower formation a bit
more challenging.

As the region continues to feel the influence of the 500mb low over
Maine, northwest low level flow will continue the cold air advection
resulting in daytime highs staying around 10 to 15 degrees below
average.

By nightfall, loss of daytime heating and a weakening of the
northwesterly flow should result in decreased cloud cover tonight
(save perhaps north of I-80). With radiative cooling, this may lend
to patchy valley fog. In areas where clearing is forecast, chances
of <40F and <36F are 40% to 60% and 5% to 15%, respectively. Areas
in eastern Tucker (WV) county has the highest chance for seeing
temperatures below 36F (25%-35%) which has resulted in the issuance
of a Frost Advisory in this area.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
KEY MESSAGES:

- Slightly warmer Sunday with a slight chance of showers for some.
- Dry and pleasant for Memorial Day.
- Increasing clouds Monday night.
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For Sunday, confidence continues to increase in a weak shortwave
trough passage. Timing agreement of the passage has increased some,
with mose CAMs having the passage during the afternoon, increasing
precipitation chances with the constructive interference with
heating. Even with shower development, coverage is expected to be
limited with slight uncertainties in shortwave amplitude. At the
worst, shower coverage could be scattered, at the best, showers
could still not happen at all. This has justified the slight chance
for  showers generally south of I-70. Cloud coverage and continued
cool 850mb air will keep temperatures 5 to 10 degrees below normal,
still.

After another cool night with clouds clearing, Memorial Day appears
pleasant and dry, with highs rebounding into the 70s for most and
the only afternoon chances or rain confined to the mountains of West
Virginia with orographics, though still only 20%. Overnight Monday,
expect clouds to build in with the approaching low that will bring
rain on Tuesday.

&&

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

- High confidence in rain by mid-week, low confidence exactly when.
- More seasonable temperatures.
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Clustered variance has improved Tuesday into Wednesday compared to
24 hours ago. All four LREF clusters have either a trough or closed
low developing across the upper Midwest by Tuesday, with surface
cyclogenesis favored on Tuesday in the upper Ohio Valley, this will
bring Gulf moisture north, allowing for rain chances to increase
into late Tuesday.

Two of the four clusters have a 30% to 40% chance of >1" of rain
over northern West Virginia, but this relies on a stronger
trough/low. Otherwise, should the trough/low be too weak or
progressive, rain may be less intense or to the northeast,
respectively.

Ensembles are in more agreement on a troughing solution by late
week, as the aforementioned wave crosses through. The primary
uncertainty will be trough speed, with a secondary emphasis on
amplitude. More progressive (faster) solutions could mean
cooler/wetter by late next week, with less progressive (slower
solutions) relating to the potential for warmer/drier weather. A
stronger trough may mean cooler, while a weaker tough may mean
warmer. The most likely temperature range for this period will be in
60s to 70s for daytime highs.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
A broken stratocu deck with VFR ceilings (minus FKL which
continues to linger at high-end MVFR) is prevailing across the
area to start the TAF period along with northwest winds around
10 knots occasionally gusting to 15-20 knots. These conditions
persist through the rest of this afternoon, perhaps seeing some
minor lifting in cigs before scattering out this evening. Light
winds and clearer skies overnight will support river valley fog
development, though minimal impacts are expected at area
terminals so mention of fog was left out of TAFs this cycle.

Another weak upper-level trough brings a thickening VFR cloud
deck to the area Sunday morning (possibly starting as MVFR
up towards FKL/DUJ before lifting to VFR). Winds remain light
and out of the northwest.

Outlook...
A weak trough of low pressure dropping southeast across the area
Sunday will have limited moisture but can`t rule out showers
in the afternoon and evening, though ceilings likely remain VFR
and most of the precipitation should stay south of the TAF
sites with possible exception of MGW.

Monday through Tuesday will likely remain free of ceiling or
visibility restrictions. Low pressure tracking up the Ohio
Valley eventually brings rain chances and restrictions back to
the area Tuesday night and Wednesday.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...Frost Advisory from 1 AM to 9 AM EDT Sunday for WVZ514.

&&

$$

SYNOPSIS...Milcarek/Lupo
NEAR TERM...Milcarek/Lupo
SHORT TERM...Milcarek/Lupo
LONG TERM...Milcarek/Lupo
AVIATION...Cermak