-- Discussion containing changed information from previous version are highlighted. --
516
FXUS61 KPBZ 272319 AAA
AFDPBZ

Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
719 PM EDT Mon May 27 2024

.SYNOPSIS...
Scattered showers and a few thunderstorms are possible again
during the afternoon as a cold front crosses the region. An
upper trough will bring rain chances and cooler temperatures
both Tuesday and Wednesday.  Dry weather returns by Thursday.

&&

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

- Scattered showers and thunderstorms will accompany a front
  this afternoon and into the evening. A few of the storms could
  be strong to potentially severe.
- Gusty wind this afternoon will diminish somewhat tonight as
  skies partially clear.
-------------------------------------------------------------------

A couple of spotty showers remain in the CWA at present, but
showers and a few storms are starting to fire just to our
northwest close to Lake Erie and southwest along an approaching
cold front. Decent mixing and a fairly tight pressure gradient
around a low near the Ontario/Quebec border is continuing wind
gusts in the 25 to 35 MPH range. These will slowly diminish this
evening as the boundary layer stabilizes and the gradient eases.

The cold front, associated with the Canadian low, will swing
through the region during the late afternoon and evening, with
most CAMs indicating scattered cell coverage. CAPE may
eventually climb into the 1000-1500 J/kg range at maximum, but
shear will be fairly marginal, with effective values in the
25-30 knot range here. Better shear and support lie to our east,
where a Severe Thunderstorm Watch has been issued. The marginal
shear, plus downdraft CAPE in the 800-900 J/kg range, could
support a few instances of hail and/or downburst wind in the
strongest storms. In this environment, SPC has continued a
marginal risk east of the PA/OH border. A marginal risk of
excessive rainfall also remains, but the expected scattered
coverage should help keep this concern minimized.

The front will exit the region this evening, taking any remaining
showers and storms with it. Some at least partial clearing can be
expected as surface ridging pays a brief visit. Despite the wet
ground, widespread fog development should largely be muted by the
ongoing mixing and a non-negligible surface pressure gradient
overnight. NBM visibility probabilities largely agree with this
thinking. Overnight low temperatures will remain a few degrees
above normal.

&&

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

- Rain chances are in the forecast both Tuesday and Wednesday,
  with the latter day featuring the most rainfall
- Thunderstorms are possible, but expected to remain sub-severe.
- Temperatures will drop below normal, as much as 10 degrees by
  Wednesday
-------------------------------------------------------------------

Mid-level troughing then takes control over the northeast CONUS
during the Tuesday/Wednesday period with fairly high
confidence. Shortwaves rotating around the low will provide
chances for showers and a few thunderstorms both Tuesday and
Wednesday, with coverage increasing during diurnally-favored
portions of each day. Rain chances still appear higher with the
stronger wave timed for a Wednesday passage, when rain totals of
0.25 to 0.50 inch appear most likely. NBM probabilities of
greater than a quarter inch are in the 50 to 70 percent range
over a good portion of the region on that day. Tuesday`s
activity will likely generate less rainfall. Thunderstorms both
days are most likely to remain sub-severe given expected
instability/shear.

Behind tonight`s front, temperatures will trend below normal,
potentially 10 degrees on the cooler side by Wednesday.

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

- Dry weather and cooler temperatures continue into Friday,
  with some warming starting on Saturday.
- Low rain chances return for Sunday and Monday in a more
  uncertain pattern.
-------------------------------------------------------------------

Surface high pressure builds into the area on Thursday, albeit under
a still-present upper trough, with decent agreement on this scenario
according to cluster analysis.  Will continue with a dry forecast
for now, but would not be surprised if a few isolated showers occur
during the day along the ridges before the trough axis works east of
the area. Below-normal temperatures are likely Thursday/Thursday
night, with lows perhaps in the lower and mid 40s.

Thereafter, an upper ridge axis builds into the region with fairly
high confidence, leading to dry weather from Thursday night into
Saturday at least. Temperatures will moderate back to seasonable
levels by Saturday.

Thereafter, spread in the models increases regarding how quickly the
upper ridge moves off/breaks down and how quickly deeper moisture
returns.  Will keep the NBM suggestion of low PoPs for now, with
temperature expectations of near to slightly above seasonal
levels.

&&

.AVIATION /23Z MONDAY THROUGH SATURDAY/...

-- Changed Discussion --
General VFR forecast overnight, except north of I-80 (FKL/DUJ),
where MVFR clouds are expected later this evening and into
Tuesday morning. Scattered showers and storms may redevelop
Tuesday afternoon along with breezy southwesterly flow.

.Outlook...
Periodic restrictions and rain chances continue through mid-
week as a series of disturbances move through the region within
broad ern-CONUS low pressure aloft.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...CL
NEAR TERM...CL
SHORT TERM...CL
LONG TERM...CL
AVIATION...Cermak