-- Discussion containing changed information from previous version are highlighted. --
120
FXUS61 KCTP 040533
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
133 AM EDT Thu Jul 4 2024

.SYNOPSIS...
Warm and humid conditions will prevail through week`s and into
the start of the coming weekend. A weakening cold front will
push in from the Great Lakes tonight, then stall out over the
area late this week. Low pressure tracking north of Pennsylvania
will drag a cold front through the state Saturday. Drier and
more comfortable conditions are expected for Sunday.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
The focus tonight will be on a an approaching, slow-moving cold
front, which lies from Western Lk Erie into Northern Indiana at
02Z. A band of convection along the attendant low level
jet/plume of highest pwats has largely dissipated as it pushed
into Northwest PA this evening. However, modest instability and
convergence along the low level jet could still support a few
showers overnight across the northwest part of the forecast
area. Mostly cloudy skies over the northwest counties and
increasing clouds elsewhere, combined with surging humidity,
will result in a much warmer night than we`ve seen recently,
with low temperatures in the mid 60s to lower 70s.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH SATURDAY NIGHT/...
Latest model guidance indicates the cold front will stall out
over Northern PA Thursday, resulting in a warm and sultry 4th
of July for Central PA. Isolated showers are possible during the
morning hours, primarily in the vicinity of the front over
Northern PA, then expect convection increasing in coverage by
afternoon, as a weak shortwave approaches from the Southern Grt
Lks. Model RH profiles suggest mostly cloudy skies are likely.
However, even modest diurnal heating of this high-pwat airmass
should yield moderate capes of near 1000 J/kg south of the
front.

Deep layer shear profiles are not especially impressive Thursday,
but the combination of instability and shear yields decent
updraft helicity values across the southern tier of the state,
where isolated late day severe weather appears possible. The
combination of instability and +2-3SD pwats could yield
torrential downpours in some parts of Southern PA Thursday
afternoon. The 12Z HREF indicates localized amounts to 3 inches
are possible across the southern tier, but dry ground in this
part of the state will limit the flash flood threat. Highs
Thursday afternoon will generally be in the 80s with a few spots
potentially reaching 90 degrees in the southeast before
convection arrives.

Passage of the shortwave and nocturnal cooling should result in
dwindling convection Thursday night. Slightly cooler air may
work into the N Mtns, as the front sags into the central part of
the state. Otherwise, expect a very warm and muggy night with
min temps in the upper 60s to low 70s.

The stalled front over Central PA is progged to return north as
a warm front Friday PM ahead of low pressure lifting across the
Grt Lks. Falling heights and surging pwats ahead of an upstream
shortwave and associated surface low lifting across the Grt Lks
should bring a round of showers/tsra in the Friday PM to
Saturday AM timeframe. Model shear/instability profiles
indicate strong to severe tsra can`t be ruled out Fri PM. The
trailing cold front should clear most of the region by Sat
morning, but could take until afternoon clear the southeast
counties, where the threat of a tsra will linger. Current
guidance suggests the mid level shortwave and bulk of the large
scale forcing will pass north of PA, leading to unimpressive
mean qpf in the ensemble plumes of 0.25 to 0.50 inches Fri PM to
Saturday. However, locally heavier amounts will accompany
stronger convection.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
All medium range guidance supports fair weather and above
average temperatures Sunday into early next week with upper
level ridging indicated over the Northeast CONUS. At the
surface, high pressure is progged to build over PA Sunday, then
pass off of the east coast early next week. The return southerly
flow should result in an uptick in heat/humidity early next
week. 18Z GEFS plumes suggest isolated PM convection is possible
Monday. However, the much better chance of showers/tsra will
come Tuesday PM with the arrival of a cold front.

There is some uncertainty with regards to how fast the cold
front clears Eastern PA Wednesday, so retaining the chance
showers that day. However, the latest ENS and GEFS currently
support a return to drier, more seasonable weather for midweek.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
A few showers have developed across the northern tier and will
continue to push eastward over the next few hours. Showers and
thunderstorms are struggling to develop and are not as
widespread tonight as originally anticipated across the northern
tier of the state. It`s possible some early morning showers
could develop across the south as a local vorticity maxima moves
across southern PA.

Ceilings will gradually lower at BFD as throughout the overnight
and early morning hours. A period of MVFR ceilings is likely
after 06Z with IFR ceilings expected after 09Z. There is fairly
high confidence that the low clouds extend down to JST with the
HREF showing a 60-70% chance of MVFR ceilings there. Elsewhere,
VFR conditions are anticipated.

As the front progresses through the area during the afternoon
today, thunderstorms will become more focused across the south.
While all sites will likely see showers at some point during
the TAF period, the exact timing of thunder will have to be
adjusted in the forecast once we have a better idea of the exact
placement of storms. Brief visibility restrictions and gusty
winds will be possible in any of the stronger thunderstorms. A
majority of the convective activity will be out of the region by
03Z tomorrow.

Outlook...

Fri...Sct TSRA w/ possible impacts; Mainly PM w/ highest
coverage across the west.

Sat...Sct to Nmrs TSRA areawide, highest chances SE in PM.

Sun...AM fog possible; otherwise, no sig wx.

Mon...SHRA possible SE late PM; otherwise, no sig wx.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...DeVoir/Fitzgerald
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald
LONG TERM...Fitzgerald
AVIATION...Bauco/Bowen