-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 251850
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
250 PM EDT Thu Apr 25 2024

.SYNOPSIS...
-- Changed Discussion --
Mostly dry weather and a warming trend is expected through
Monday save chances of isolates showers or storms Saturday and
Sunday afternoon.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
KEY MESSAGES:

- Freeze warnings and frost advisories are in effect for
  portions of the area, beginning at midnight.

------------------------------------------------------------------

Mundane weather will persist as the area sits underneath a
subsidence inversion in a weak pressure gradient. For this
reason, winds are expected to remain calm to light through the
near term.

A weak 850mb meso-low has been observed across southwest
Pennsylvania, allowing weak low-level convergence and moisture
pooling in the area just south of I-80. This has allowed
stratocumulus decks to persist for much of the day as mixing has
attempted to erode them. The current thinking is that most
cumulus will dissolve with sunset, but patches of stratocumulus
may linger in the aforementioned area overnight. Low-
probability clouds are also possible in the Laurels with
upsloping.

Areas that are clear at this point will likely remain clear and
there is a high probability that low temperatures tonight will
under-perform guidance, thus, adjusted towards the NBM 10th
percentile with calm winds. Should clouds linger a bit longer,
temperature will likely run higher than the forecast.

Frost advisories were hoisted based on the areal extent of 36
degrees or lower across a forecast zone after adjusting
nocturnal temperatures down. The same goes for freeze warnings;
there is a high probability of a freeze for Forest, and a
moderate probability of a freeze for Venango, Clarion, and
Jefferson PA. In these zones, calm winds and clear skies are
high probability.
-- End Changed Discussion --

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
-- Changed Discussion --
KEY MESSAGES:

- Dry and warmer through Friday
- Showers and possible thunderstorms return Friday night into
  Saturday with a warm front

----------------------------------------------------------------

The center of the surface high will shift east of the region on
Friday, as upper ridging builds eastward across much of the
Eastern CONUS. Rising 1000-500 mb heights, and warm advection,
should drive temperatures back to or just above average for this
time of the year.

The upper level ridge axis is expected to move just east of the
region Friday night and Saturday, as warm, moist advection
tracks across the Upper Ohio Valley region in SW flow aloft.
A surface warm front is also expected to lift NE across the
region, with scattered to numerous showers moving across the
region. A rumble of thunder is possible with limited
instability across NW PA and eastern OH. The showers should
taper off from SW-NE through the afternoon as the front lifts
north of the region, and the upper support exits.

Generally dry weather is expected for most of the region
Saturday night as a ridge becomes reestablished across the SE
CONUS, and extends northward to the Upper Ohio Valley region. A
few showers will still be possible across far NW PA as a weak
vorticity max crosses on the northern periphery of the ridge. A
noticeable warming of overnight lows is expected, with readings
around 15 degrees above average by Saturday night.
-- End Changed Discussion --

&&

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

- Warm with minimal chances of afternoon thunderstorms Sunday
  and Monday
- More widespread showers and possible thunderstorms with a
  Tuesday cold front
-------------------------------------------------------------------

Model ensembles continue to indicate the strongest riding across
the Upper Ohio Valley region Sunday and Monday. Sunday should be
mainly dry under the ridge, with warm air aloft limiting
convective potential. Still, an isolated afternoon storm or two
is possible, mainly north of Pittsburgh, where another vort max
moves across southern Ontario on the northern periphery of the
ridge.

Similar conditions are expected Monday. The ridge axis is
expected to shift slowly eastward later Monday, with slightly
better chances for afternoon showers and thunderstorms late in
the day as a shortwave trough and associated surface cold front
begin to approach from the Midwest.

Showers are likely, along with a few thunderstorms, on Tuesday
as the trough and cold front cross the region. The precipitation
should end Tuesday night as the front exits.

Greater uncertainty exists on Wednesday, with differences in the
strength and timing of a trough approaching from the Upper
Midwest. Stayed close to the ensemble blend, resulting in shower
and possible thunderstorm chances returning through the day.

Temperatures mainly in the 80-85 degree range (outside of the
higher terrain) are expected Sunday and Monday with a 1000-500
mb height of 582 dm, and 850 mb temperatures ranging from 12-14
deg C. Cooler, but still above average, temperatures should
return Tuesday behind the front.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
Stratocumulus continues across a significant portion of the
forecast area early this afternoon while ceilings have generally
lifted to low-end VFR (3-5kft). Some erosion is beginning to
take place along the southern border of this cloud deck per
latest visible satellite imagery as MGW/ZZV have scattered out
to mostly sunny skies. This trend should continue through the
rest of the day with most of these clouds clearing by late
evening, though some patches of scattered/broken coverage may
linger into overnight hours. Winds are light across the area and
should remain that way through the night before a strengthening
and better established southeast flow sets up after 12Z Friday.

.Outlook...
VFR conditions are expected Thursday and Friday.

The probability of showers and isolated thunderstorms increases
Friday night into Saturday which will come with increasing
probabilities for restrictions as well.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
PA...Frost Advisory from midnight tonight to 9 AM EDT Friday for
     PAZ007-013-014-020-022-077-078.
     Freeze Warning from midnight tonight to 9 AM EDT Friday for
     PAZ008-009-015-016.
OH...Frost Advisory from midnight tonight to 9 AM EDT Friday for
     OHZ039>041-048>050-057>059-068-069.
WV...Frost Advisory from midnight tonight to 9 AM EDT Friday for
     WVZ001.
-- End Changed Discussion --

&&

$$

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