909
FXUS61 KPBZ 300621
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
221 AM EDT Tue Apr 30 2024

.SYNOPSIS...
Rain chances increase early Tuesday morning with an approaching
trough. Above average temperatures will continue overnight and
into Tuesday afternoon under southwest flow.

&&

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

- Dry, quiet weather is expected through midnight under high
  pressure.
- Precipitation chances increase early Tuesday with an
  approaching trough from the west.
- Near record high min temperature Tuesday morning is possible.
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6:30pm update: No major changes have been made to the forecast
period. A new record high temperature was set at DuBois, PA
(82F), this breaks the old record 80F set in 1970.

Previous Discussion:

Eastern CONUS ridge will remain positioned just off the east
coast and residing over the region today as an upper level low
lifts toward the western Great Lakes. Warm air aloft and
subsidence will cap any convection, keeping dry conditions in
place and allowing for plenty of sunshine. Near to record high
temperatures are possible at all climate sites.

Ridge axis will shift eastward tonight and Tuesday as a
shortwave trough will push the dome of high pressure toward the
east coast. An increase in cirrus clouds tonight should keep
overnight lows warm. Near to record high minimum temperature at
most climate sites could result. This could also be a case where
early convection arrives late tonight in some of the
northwestern or western counties. This will of course impact the
low temperatures across the region as well.

&&

.SHORT TERM /TONIGHT THROUGH 6 PM WEDNESDAY/...
KEY MESSAGES:

- Showers and thunderstorms return Tuesday.

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Upper level trough will weaken as it slowly crosses the region
on Tuesday. This loss in amplitude will result in a slower
crossing of a weak surface cold front. Shortwave trough movement
will dictate rainfall timing with the trends continuing to slow
the progression of the showers. This would result in rainfall
chances continuing into Tuesday night. Any severe threat will
depend on strength of that passing shortwave. It still appears
that the severe threat will be limited given excessive cloud
cover and residual warm air aloft. Thus the main concern for
missing parameters will be the lack of instability but plenty of
shear present. Thus is not out of the question to get a gusty
shower for Tuesday afternoon. However, the DCAPE values will be
a bit lacking with values around 500 J/Kg making the downburst
potential really lacking.

Height rises are likely to return on Wednesday, promoting dry
conditions and well above normal temperatures. It is certainly
not out of the question to still be dealing with a few showers
exiting the forecast area on Wednesday morning but overall, a
warm and dry forecast is on tap.

&&

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

- An unsettled pattern continues through the long term with
  above-average temperatures favored.

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High pressure will provide well above normal temperatures and
dry conditions through Thursday night. Ensembles favor upper
level trough movement through the Great Lakes region Friday into
the weekend that would push the ridge axis southeast and
introduce widespread shower and thunderstorm chances. Timing of
said pattern shift (which will play role in precipitation timing
and temperature trends Friday into Saturday).

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
VFR will prevail through the overnight hours, though a remnant
outflow boundary from convection off to our west will progress
through the area and provide a quick wind shift from
southwesterly to northwesterly with upstream obs indicating an
increase to about 10 knots with its passage. Expect that it
should weaken with eastward progression and have not included
mention for LBE/MGW/ZZV. Otherwise, wind will prevail at 5 knots
or less. Increasing mid/high clouds will overspread ahead of an
approaching cold front.

Moisture will increase and CIGs will lower into Tuesday morning
with MVFR probabilities increasing to 40-60% across the area
with the arrival of rain showers. Latest mean hi res ensemble
timing for precipitation onset is after 11z at ZZV, 15z at PIT,
and 18z at LBE. Scattered thunderstorms are possible in the
afternoon, and have included a TEMPO group during the timeframe
of highest SREF/NBM thunder probabilities. There may be some
VIS restriction as well, especially if any thunderstorm impacts
a terminal, but confidence in the time or spatial coverage of
thunder was too low at this point to include.

Wind will shift to the northwest with frontal passage overnight
Tuesday night as high pressure quickly builds. There is low to
moderate 30-50% confidence for areas of fog toward sunrise
Wednesday with ensemble probabilities maximizing primarily south
of PIT. This is conditional on whether or not wind remains
elevated overnight and likely focused on areas that receive the
most rain.

.Outlook...
VFR will return on Wednesday and Thursday under high pressure.

&&

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

&&

$$

SYNOPSIS...Hefferan
NEAR TERM...Hefferan
SHORT TERM...Shallenberger
LONG TERM...Shallenberger
AVIATION...MLB