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027
FXUS61 KPBZ 301746
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
146 PM EDT Tue Apr 30 2024

.SYNOPSIS...
Rain chances increase today with an approaching trough,
followed by dry weather mid week before rain chances return next
weekend. Above normal temperatures are forecast through the
entire 7 day period.

&&

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

- Showers and thunderstorms expected along a weak cold front
  moving through the area.
- Temperatures remain a few degrees above normal today and
  tonight.

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With a largely stratiform rainfall mode as of 10am, the
excessive rainfall outlook has been pulled back to portions of
north-central Pennsylvania. Morning satellite observations
ahead of precipitation and east of Pittsburgh may allow enough
instability for shallow shower or storm generation with training
potential. Probabilities of any storms are greatest in the
vicinity of Forest County, though excessive rainfall concerns
have diminished across the board with less instability than
anticipated and decaying returns.

Previous discussion...The upper ridge that brought warm and
mostly dry weather to the area the past couple days shifts to
the east this morning, centering over the eastern seaboard or
just off the Atlantic coast. With this shift, an upstream
shortwave trough lifts northeastward over the Great Lakes, with
an attendant cold front slowly meandering through the area
during the day today. Showers are ongoing along this front and
will move through the area this morning and afternoon. A few
thunderstorms will be possible mainly in the late morning and
afternoon with daytime heating providing limited instability
(MUCAPE < 500 J/kg).

There is no threat for severe weather with this system, and
while widespread rainfall amounts should remain at or below a
half inch, rainfall rates in thunderstorms could reach or
exceed 0.5 in/hr and therefore locally higher amounts up to
0.75-1.0 inches may be observed in any locations that see
multiple rounds of thunderstorms. This presents a low-end threat
for flooding (particularly in low-lying and urban areas), which
is reflected in the NWS Weather Prediction Center`s Excessive
Rainfall Outlook, which highlights a Marginal Risk area
expanding across much of eastern OH, western PA, and northern
WV today. Meanwhile, high temperatures this afternoon are
expected to range from the low to mid 70s, with the warmest
temperatures occurring farther east where the clouds/rain will
arrive later and allow for a longer period of heating.

Showers and storms depart the area to the east by or shortly
after sunset, followed by a dry rest of the night and
temperatures dropping into the upper 40s to low 50s.

&&

.SHORT TERM /WEDNESDAY/...
KEY MESSAGES:

- Dry weather and above-normal temperatures expected Wednesday
  and Wednesday night.

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Height rises are likely to return on Wednesday as a weak upper
ridge builds back overhead, promoting dry conditions and above
normal temperatures. Another weak front pushes into the area
Wednesday night and stalls, but with overall subsidence
expected to be ongoing beneath the upper ridge, it`s unlikely
that anything more than a stray shower or thunderstorm are able
to develop and the best chance for that would be over northeast
OH and northwest PA. Temperatures Wednesday afternoon should reach
the upper 70s to low 80s before dropping back down into the 50s
Wednesday night.

&&

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

- Warm and dry weather expected under high pressure on Thursday.
- An unsettled pattern returns Friday through the weekend with
  above-average temperatures and periods of showers and
  thunderstorms favored.

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High pressure will continue to support above-normal temps and
dry conditions through Thursday night. Ensemble guidance
indicates the best chance for Thursday afternoon highs to exceed
80 degrees occurs south of I-80 where widespread probabilities
are 70% or greater. Lower probabilities (<50%) exist along and
north of I-80, where temperatures are more likely to top out in
the upper 70s. Lows Thursday night similarly range from upper
50s south of I-80 to low 50s farther north.

Ensembles continue to favor upper level trough movement through
the Great Lakes region Friday into the weekend that would push
the ridge axis southeast and lead to a return of more active
weather. While this more active pattern certainly increases
chances for showers and thunderstorms, it also introduces
greater uncertainty and makes it more difficult to narrow down
details regarding exact timing and intensity. According to the
latest ensemble runs, Saturday appears to be the most likely day
for widespread rainfall, though chances really begin to ramp up
Friday afternoon and could linger straight through the weekend
and into next week. Stay tuned for more on this as we get closer
to the weekend.

As for temperatures, at this time Friday appears to be the
warmest day of the period with highs potentially reaching the
mid to upper 80s across much of the area. In fact, ensembles
already indicate a 70% or greater chance of areas south of I-80
exceeding 85 degrees. Temperatures Saturday through Monday also
trend above normal, but could remain in the 70s due to thicker
cloud cover and a greater coverage of showers and thunderstorms.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
-- Changed Discussion --
A line of showers pushing east ahead of a weakening cold front
will continue to run into dry air and subsidence in western PA.
Daytime heating and some clearing was present on the central PA
side. Thus, this region will see the bulk of the thunderstorm
development. It is likely that only DUJ and LBE have the best
chance for development. Otherwise, isolated MVFR conditions will
be in place at the terminals through some of the evening. Some
IFR conditions may develop tonight.

Wind will shift to the northwest with frontal passage overnight
tonight 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 if any.

.Outlook...
VFR will return on Wednesday and Thursday under high pressure.
-- End Changed Discussion --

&&

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

&&

$$

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