978
FXUS61 KCTP 251023
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
623 AM EDT Wed Sep 25 2024

.SYNOPSIS...
* An upper trough and surface frontal system will bring overcast
  skies and showery conditions to Central PA through Thursday
* Soon-to-be-Hurricane Helene will remain well southwest of
  Pennsylvania late this week, though a stationary front draped
  across the Mason-Dixon Line will keep showers in the forecast
  each day through the weekend.
* Beneficial rainfall accumulation expected into next week for
  most as October kicks off.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Broad southeast flow continues this morning and will keep
overcast skies in place all day. Showers and a few rumbles of
thunder ongoing in NW PA associated with convergence/warm
advection will drift northeast this morning. Drizzle/light
showers will remain possible through much of the morning before
more robust showers associated with a warm front lift
northeastward. SPC has kept all of Central PA in a General
Thunder area, though current thinking is that best instability
will be confined to the Laurels this afternoon.

Generally light rainfall accumulations expected today, with only
spot amounts over a quarter inch of rain. Diurnal temperature
ranges progged to be a modest +5 to +8 thanks to overcast skies
and a moist airmass.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...
The center of an upper trough will cross Quebec tonight into
Thursday, helping focus a bit more lift across PA. At the
surface, a weak front will drift through and provide enough lift
to generate a more concentrated corridor of showers and perhaps
a thunderstorm or two. Modest PWATs around 1.5" could produce
some heavier rainfall, perhaps up to an inch with stronger
showers/storms on Thursday afternoon. As the upper low moves to
the northeast of PA Thursday evening, the associated upper level
support will help sustain showers in northeast PA as a lull in
the precipitation follows in western and Central PA in the wake
of the cold front.

The front will stall out across the Mason-Dixon Line Thursday
night. As such, a few breaks in the clouds may occur Thursday
afternoon in northwest PA. Farther south, the stretch of
overcast conditions continues. A very mild night is in store
Thursday night with lows ranging from +10 to +20 compared to
average for this time of year, ranging from the middle 50s in
the north to middle 60s farther south.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Rain remains in the forecast through the weekend. 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 /10Z WEDNESDAY THROUGH SUNDAY/...
TAFS in good shape overnight, with just some minor adjustments
so far. Main item of interest is the thunderstorm to the
southwest of BFD. Keeping an eye on it, but trend has been
for the storm to weaken. The storm should stay a bit west of
the BFD area.

Main issue today will be MVFR to IFR conditions today into
early Thursday, as a southeast flow of cool, moist air is
advected to the north and west into the mountains.

CIGS will likely not go up a lot today, as showers become more
wide     spread. However, the time of day should aid in CIGS
getting a bit higher.

Any improvement will not last, as CIGS will likely trend back
down some as the sun sets.

Outlook...

Thu...AM low cigs/chc showers, mainly early.

Fri...Patchy AM valley fog possible N Mtns. Chance of showers/low
cigs across the south.

Sat-Sun...Chance of low cigs/showers, mainly across the south.

&&

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

&&

$$

SYNOPSIS...Banghoff
NEAR TERM...Banghoff
SHORT TERM...Banghoff
LONG TERM...NPB
AVIATION...Martin