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450
FXUS61 KCTP 061948
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
348 PM EDT Mon May 6 2024

.SYNOPSIS...
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Isolated to scattered showers and thunderstorms are expected
across south central PA through this evening. After a lull
Tuesday morning and afternoon, scattered showers and a few
storms are likely for Tuesday night into Wednesday. More
widespread showers are expected Thursday night into Friday with
unsettled and cooler conditions lasting into the weekend.
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&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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A weak cold front dropping through the area will maintaing
scattered showers and a few storms as it drops to the Maryland
border this evening. Best chance for lightning strikes will be
across the Laurel highlands, where MLCAPE is progged to reach
750-1000 J/kg. Meanwhile, enough dry air will nudge into
northern PA for a few peeks of sunshine.

Most model guidance shows the convective activity along the
southern tier waning tonight with the loss of daytime heating,
but isolated to scattered light rain showers will likely
persist. Some fog is possible tonight as well, though
confidence in fog is not as high as it was last night. Low temps
will range form the mid 40s along the NY border to around 60F
in the southern tier, with the north to south gradient in
moisture playing a large role in overnight cooling.
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&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
Upper level ridging over PA indicates warmer conditions are
likely Tuesday with highs reaching the upper 70s to near 80F. A
warm front lifting out of the Ohio Valley, a 500mb short wave
trough, and 850mb warm air advection pattern will result in
increasing clouds with a PM shower/tsra, primarily across the
western counties. Showers and a few storms will overspread the
area Tuesday night as the warm front progresses northeast. MU
CAPE during this time is likely to increase to near 1000 J/kg
and support widespread thunderstorm activity.

Low temperatures Tuesday night will dip to the low 60s across
the northern tier of the CWA and remain in the mid 60s in the
Lower Susquehanna Valley.

Unsettled weather will continue into Wednesday and Thursday.
Wednesday looks to be another warm day, with ensemble mean 850mb
temps of 16C suggesting max temps well into the 80s across the
Lower Susq Valley. Upper-level divergence overhead will be
supportive of widespread showers and thunderstorms as the large
scale upper level trough swings across the state. An 850mb LLJ
will also be in place on Wednesday and Thursday during the 9-15z
time frame, supporting late night/early morning convection. The
SPC has outlined this threat with a MRGL SWO for Wednesday
night/Thursday morning.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
A notable trend toward cooler conditions for late this week
through the coming weekend as a broad trough develops over the
Glakes and Eastern U.S. with several smaller scale shortwaves
moving southeast within the northern branch of the upper jet.

The surface low and deepest moisture is progged to shift east
of the area Thursday night. However, falling heights ahead of
the positive tilt upper trough (and cold 700 mb temps falling to
around -4C) will likely support scattered-numerous, mainly
diurnal showers Friday through Sunday. A low-topped tsra cannot
be ruled out Friday afternoon/early evening.

GEFS mean 850 mb temps slip to between +2 and +4C (or about -1
sigma) Friday night through Saturday, before rebounding a few
deg C Sunday into Monday. Mean 925 mb temps of just 8-10C later
Friday through Sat morning will likely top even cooler LLVL air
under cloudy conditions.

This cool airmass (with Canadian origin and trajectory over
Lake Erie waters still in the upper 40s to around 50F) will
combine with numerous late morning through early evening showers
across at least the Central and Northern part of the CWA Friday
to likely yield the coolest day we`ll see til this Autumn with
high temps staying in the U40s in some spots across the Northern
Mtns. Highs in the mid 50s to mid 60s will be common heading
southeast from the Allegheny Front.

Temps will still be 2-5 deg F below normal over the upcoming
weekend with mins at night near to a few deg F above normal due
to varying amounts of clouds and at least a light breeze, which
should limit any potential for frost to the patchy variety and
confine it to the Northern Mountains Sat, Sun and Mon mornings.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
Conditions have improved to mainly VFR for much of Central and
Northern PA this afternoon. Lingering MVFR over the Scent and
Southeastern PA could briefly lift to brief VFR between 20Z-23Z
Monday. However, low pressure lifting up the Ohio Valley will
likely spread showers and reduced cigs into the southern tier of
PA Monday evening.

Conditions should slip back through MVFR to IFR in Central and
Southern PA tonight through the mid morning Tuesday with areas
of LIFR in fog and low cigs possible for 2-4 hours centered on
daybreak Tuesday across the Middle and Lower Susq Valley.

In contrast, high pressure building into northern PA from the
Grt Lks, will push drier air into that part of the state,
keeping conditions mainly VFR there through tonight.

A warm front lifts northeast across Western and Central PA
Tuesday afternoon and night, leading to a trend toward
increasing areal coverage of showers and thunderstorms and a
higher frequency of MVFR and brief IFR conditions.

Outlook...

Tue...AM low cigs/showers possible southern tier of PA.
Scattered evening tsra impacts possible W Mtns.

Wed...AM low cigs/tsra possible.

Thu...Periods of rain/low cigs likely. Scattered afternoon
TSRA.

Fri...Showers with periods of low cigs possible.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SYNOPSIS...DeVoir
NEAR TERM...DeVoirBowen
SHORT TERM...Colbert/Bowen
LONG TERM...Lambert/Fitzgerald/Colbert
AVIATION...Lambert/RXR