178
FXUS61 KCTP 220435
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1235 AM EDT Sun Sep 22 2024

.SYNOPSIS...
A frontal system will fall apart as it moves through Central PA
overnight accompanied by scattered showers and thunderstorms.
Mostly cloudy, but rain- free weather returns for Sunday, before
a slow-moving trough brings the next chance of rain from Monday
through midweek.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Strong shortwave driving southward across the Lower Susquehanna
River Valley maintaining deep convection well past the midnight
hour, with marginally severe hail and wind gusts in excess of
45 kts within cells embedded within Cumberland, Dauphin,
Lebanon, York and (soon to be) Adams Counties as of 0430Z.
Once the aforementioned shortwave clears the PA/MD border,
stable stratification arrives and activity will wind down
after 06z. Heavy rain/flash flooding threat has diminished over
the past 2 hours thanks to more progressive storm motion as the
shortwave drops southeastward, while hail and wind gusts are
still marginally severe for the next 1 to 1.5 hours.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM MONDAY/...
Forecast soundings indicate an upsloping southeast flow will
result in persistent stratus and perhaps a bit of fog or drizzle
over the central/east zones for Sun and Sun night. The cloud
cover and flow off of the Atlantic should result in markedly
cooler afternoon temps Sunday than on Saturday, with highs
likely stuck in the 60s over the Central Mtns. Sun night looks
mainly dry with prev anticipated forcing holding off a bit
longer/later.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Surging PWATs with enhanced energy from an upper-level trough
will bring about an unsettled pattern throughout much of the
long-term period. Deterministic model guidance is in fairly good
agreement that low-pressure stationed over the southern Great
Lakes will bring about shower activity on Monday; however, model
guidance has trended slower with the onset of rainfall and have
chopped PoPs throughout the early period of the day as models
tend to converge on a (slightly) slower progression. The best
chances of showers will come across the Laurel Highlands during
the late morning hours, continuing eastward throughout the
afternoon/evening hours. Elevated instability will be highest
across the western third of the area, so have limited mentions
of storms to this area during the PM hours.

Model guidance outlines another surface low-pressure system
tracking northeastward across western portions of the Upper Ohio
Valley and into southern Ontario Tuesday into Wednesday, with
slightly more moisture and lift available as the warm front
aligns itself north-to-south across west-central PA. Given
slightly better lift with this low-pressure system coupled with
enhanced moisture, have retained likely PoPs in the Tuesday to
Wednesday timeframe. Given PWATs in the 1.50-1.75" range on
Wednesday, locally heavy rainfall will be possible and this has
been outlined with marginal (level 1/4) risks in the D4 (W) and
D5 (E) Excessive Rainfall Outlooks from the Weather Prediction
Center. Impacts at this time look less likely at this time given
ongoing dry conditions across especially SW PA where D2 drought
conditions persist; however, any heavier rainfall in the
preceding days could allow for slightly more impacts.

As we shift into the later part of the week, slightly more
model uncertainty with regards to low-pressure moving N/E of the
area and how this will impact rainfall chances for Central PA.
At this time, have capped PoPs at a chance for Thursday as the
low-pressure system will be slightly closer to our eastern half,
and capped at a slight chance for Friday, keeping close to NBM
model guidance in this timeframe.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
Late this evening showers and thunderstorms will continue affect
most TAF sites except, most likely, for KAOO/KJST.

Overnight, medium to high confidence in IFR/LIFR across central
Pennsylvania. GLAMP model guidance and HREF probabilities
continue to suggest fog formation, so have trended towards GLAMP
guidance this cycle. As sunrise approaches, very slow
improvement is expected with the bulk of airfields expected to
stay sub-VFR through 18Z Sunday with exceptions at BFD/JST.

Outlook...

Mon-Thu...Scattered showers, restrictions possible.

&&

.CLIMATE...
The high temperature in Bradford on Friday set a new record
high of 82 degrees. This broke the record of 81 degrees set in
1978 and 2016.

The first day of autumn 2024 (Fall Equinox) begins at 8:44 am
EDT on Sunday September 22nd.

&&

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

&&

$$

SYNOPSIS...DeVoir/Dangelo
NEAR TERM...DeVoir/Dangelo/Gartner
SHORT TERM...Dangelo/Gartner
LONG TERM...Gartner/NPB
AVIATION...Gartner/NPB
CLIMATE...Steinbugl/Martin/NPB