524
FXUS61 KCTP 261911
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
311 PM EDT Thu Sep 26 2024

.SYNOPSIS...
*Mostly cloudy with periods of rain and mild nights through the
 last weekend of September; showers continue to start October
*The heaviest rain over the next 5-7 days is expected over south
 central PA which should be largely beneficial
*A shift toward drier/cooler weather is possible by the end of
 next week/first weekend of October

&&

.NEAR TERM /THROUGH TONIGHT/...
Cloudy and mild/humid this evening and overnight with a couple
of rain showers. Max POPs are in the southern tier of the
forecast area or closer to wavy frontal zone sinking slowly to
the south toward the MD line. Min temps will be +10 to +20
degrees above the historical average for late September ranging
from the upper 50s in the northern tier to the upper 60s in the
lower Susq. Some areas of fog may also develop early tonight,
but could dissipate as an ENE wind picks up into Friday morning.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
Increasingly strong and anomalously moist (PW 1.5-2") low level
flow from the south/southeast will overrun the aforementioned
frontal zone on Friday. This will result in plenty of clouds
with shower activity expected to expand from south to north
through Friday night into Saturday morning. A tight pressure
gradient on the northeast side of ET/PT Helene (merging with
an upper low centered near the the Bootheel of MO) will promote
wind gusts up to 40 mph on the Laurel ridges tomorrow.

The phased deep layer cyclone will move very slowly to the
northeast toward the IN/KY/OH border and gradually
unravel/weaken through the last weekend of September. A moist
east to southeast low level flow will maintain periods of
showers with a consensus QPF max between 1 and 2 inches focused
over the favored upslope terrain across south central PA.

The cloudy, moist/humid, and showery weather pattern favored
incorporating (blending) the 25th percentile NBM for daytime
highs and 75th percentile NBM for nighttime lows. This idea of
trending cooler during the day and warmer overnight fits the
pattern playbook quite well.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
An upper-level low over the Ohio Valley will 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.

High pressure building in behind the front will bring drier
weather and cooler temperatures for the end of the week. Highs
will generally be in the 60s with overnight lows in the 40s.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
Scattered showers will continue through the rest of the
afternoon and may cause brief periods of IFR visibilities if
they move directly over any airfields. The general trend
through the day though has been towards higher ceilings with
many sites reporting VFR ceilings as of 18Z.

By later this evening (01-05z), the expectation is that cloud
bases will lower again to categorical IFR reductions, especially
over the southern half of Central Pennsylvania where the HREF
shows a 80-90% chance of ceilings below 1000 feet. Surface
winds of 5-8 kt from the E-SE can be anticipated this afternoon,
with otherwise light and variable winds less than 5 kt.

These low clouds will slowly rise to MVFR across the western
half of the region during the late morning and early afternoon
on Friday, though model soundings suggest that IFR ceilings
remain likely across the southeast through at least 18Z.

Outlook...

Fri...Lower ceilings are likely area-wide in the morning, then
during the afternoon the best chance of showers/low ceilings
will be across southern PA.

Sat-Mon...The highest probabilities for low ceilings and
showers should again be across southern PA.

Tue...Scattered showers with restrictions possible.

&&

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

&&

$$

SYNOPSIS...Steinbugl/Banghoff
NEAR TERM...Steinbugl/Banghoff
SHORT TERM...Steinbugl/Banghoff
LONG TERM...Dangelo/Bauco
AVIATION...Jurewicz/Bauco