423
FXUS61 KCTP 241937
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
337 PM EDT Tue Sep 24 2024

.SYNOPSIS...
An amplifying upper level trough and slow moving frontal
system will bring showery conditions to Central Pennsylvania
through at least Wednesday, along with a few rumbles of thunder.
As such, it will be cloudy and cool through midweek. The latter
part of the week looks milder with at least partial sunshine
expected into the weekend.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Storms headed for SW at 19Z are organized into a little bow
echo. They are approaching our fairly stable CWA. This usually
helps keep the strong winds from mixing down. But, we`ll monitor
closely mas SPC MRGL risk gets right up to Somerset Co. CAMs
keep this bath of TSRA as the best/heaviest precip for the
evening. The forcing passes through and into the central mtns,
and deeper into the stable air overhead. Much of the overnight
will be just cloudy and drizzly. However, more organized
precip/showers move into the srn counties after 06Z and slide
over the Lower Susq, mainly S of the Turnpike.

Temps won`t move much (down maybe only 5-8F thru the entire
night, again) and need little editing in the grids.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Upper ridging continues to pump up, more so to our east then
overhead. The low pressure center associated with all this
light rain will slide generally northward. This will mean a
prolonged time of similar conditions. The moisture feed/PWAT
gets a bit less favorable over the west, but stays in the 1.75"
range in the SErn counties. Basin average QPF is less than half
of an inch over all of the area, and many places will have less
than a quarter of an inch across the short term period (Wed-Wed
night). Again, little change to temps across the 24 hours. Will
stick with continuity on temps. Sky cover pretty solid for most
of the time on the deep SE flow.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Lingering showers across mainly E PA will continue into
Thursday before a brief reprieve in rainfall. Shower chances
will increase Thursday afternoon into the morning hours of
Friday with the surface cold front lingering across southern
Pennsylvania. The highest chances will mainly be confined south
of the Turnpike; however, can`t rule out showers making it as
far north as the northern tier Friday evening into Saturday
morning with Chc PoPs across the Laurels throughout the day on
Friday and into Saturday morning.

There is still some uncertainty in regards to how Helene will
impact central Pennsylvania, mainly dependent on interactions
with an upper-level low stationed across the eastern Tennessee
Valley. Deterministic model guidance has outlined that the bulk
of rainfall will stay west of the area while a rather
narrow, negatively tilted upper-level ridge holds strong from
the Great Lakes through the Upper Ohio River Valley. Given the
uncertainty with regards to upper-low interactions, did not
deviate much from continuity and NBM guidance this cycle.

The upper-level low and remnants of the tropical system will
likely drift east across the Commonwealth early next week,
bringing increased chances of shower activity into the beginning
of next week, with highest chances generally across the western
highlands.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
IFR/MVFR ceilings are expected to persist throughout much of
the area for the 18Z TAF package with moderate-to-high (60-70%)
confidence as SHRA/TSRA begin entering central Pennsylvania.
Stable air will allow for the bulk of TSRA to decay as it
continues to approach JST/AOO so have limited TSRA mentions
throughout the near-term but have included borderline LIFR
ceilings based on increasing moisture in the low-levels. Some
localized drops towards 1SM will remain possible in the heaviest
showers; however, generally lower confidence in
timing/placement of the heaviest restrictions so have kept these
mentions out of the 18Z TAF package. Further east, have kept
mentions to MVFR at MDT w/ low-end VFR ceilings at LNS; however,
generally expect ceilings to become lower in the 23-01Z period
as SHRA edges slowly towards the airfield.

Moving into the overnight period, moist low-levels will allow
for a continuation of lower ceilings with IFR/LIFR conditions
the most plausible solution at all airfields outside of the LSV
airfields (MDT/LNS). As SHRA continues into the overnight at
MDT/LNS, generally expect ceilings to continue into the 10-12Z
Wednesday timeframe to trend lower w/ increased moisture. After
sunrise, little improvement is expected throughout the daytime
hours with model guidance indicating scattered SHRA. At this
time, have trended closer to GLAMP guidance due to some
remaining uncertainty that will need to be evaluated in future
TAF packages.

Outlook...

Thu...AM low cigs/showers likely.

Fri...SHRA increasing across S PA.

Sat-Sun...Chance of low ceilings/SHRA.

&&

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

&&

$$

SYNOPSIS...Lambert/Dangelo
NEAR TERM...Dangelo
SHORT TERM...Dangelo
LONG TERM...NPB
AVIATION...NPB