945
FXUS61 KCTP 252305
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
705 PM EDT Wed Sep 25 2024

.SYNOPSIS...
Damp and unsettled weather will persist into Thursday, with
perhaps a brief break Thursday night into early Friday. A
stationary front draped across the Mason-Dixon Line will bring
an increasing chance of showers for late Friday and into the
weekend. A steadier period of rain is possible over parts of
Central Pennsylvania Saturday night or Sunday as the weakened
moisture remnants of Helene very slowly pull away from the
region.

&&

.NEAR TERM /THROUGH THURSDAY/...
Easterly ageostrophic flow and western Atlantic component being
overrun by moisture WSW flow at 850mb and above, yielding dense
low clouds cover and widespread drizzle and patchy light rain
this evening. Current conditions will persist for most of
tonight and Thursday, as central PA remains sandwiched between
an upper- level trough crossing New England and upper low
centered over the Lower Ohio Valley.

Blanket of clouds will keep overnight temperatures mild, with
lows in the upper 50s to mid 60s running about 15 degrees above
normal for late September. Thursday should be a bit milder
than the past few days, with highs expected to reach the 70s
areawide.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
The upper-level trough over New England will pull off the
Atlantic Coast Thurs night into Friday, while the remnants of
Hurricane Helene become wrapped up in the upper low over the
Lower Ohio Valley.

At the sfc, a stationary front will become draped across
southern Pennsylvania. We will have to see how the remnant
moisture from Helene interacts with the stationary front. The
presence of this front could keep showers in the forecast into
this weekend, esp across southern PA.

Temperature-wise, the days will see temperatures fairly close
to average, while clouds will keep nighttime temperatures well
above average for early fall.

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.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
An upper-level low over the Ohio Valley will likely drift east
across the Commonwealth into the beginning of next week, keeping
rain chances around through at least Tuesday. Uncertainty begins
to increase towards the middle of the week as a northern stream
shortwave tracks near the region, bringing a cold front along
with it. The timing of this feature is a little unclear with
some ensemble members showing the front tracking through early
Wednesday morning while others show a later frontal passage.
Moisture appears to be limited ahead of the front and the best
forcing looks to remain to our north, so widespread rainfall
does not appear likely at this point.

Most guidance shows high pressure building in behind the front
which will bring drier weather and cooler temperatures. By
Wednesday, expect high temperatures in the upper 50s and 60s and
lows mainly in the 40s.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
IFR ceilings are expected to persist through the rest of the
day and into Thursday morning along with scattered showers and
potentially a thunderstorm. Model soundings support widespread
ceilings below 500 feet overnight at all airfields, and the HREF
suggests a 30 to 40% chance of fog developing across the
northern half of Central PA.

Ceilings may slowly rise into Thursday afternoon with most
guidance showing MVFR ceilings in the northwest after 15Z while
the rest of the airfields likely remain IFR. Scattered showers
will continue into the early afternoon.

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

&&

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

&&

$$

SYNOPSIS...DeVoir/Evanego
NEAR TERM...DeVoir/Evanego
SHORT TERM...Evanego
LONG TERM...Bauco/NPB
AVIATION...Bauco