520
FXUS61 KCTP 231829
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
229 PM EDT Mon Sep 23 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 late this week and into the weekend.

&&

.NEAR TERM /UNTIL 7 PM THIS EVENING/...
The steadiest rain is pushing out of the NW mtns, but a good
mid-level short wave trough/MCV is moving across LE. This
feature will probably create sct, weak/light convective rainfall
across the entire area this aftn and evening. The best slug of
rain should diminish as it tries to push more east. But, still
end up making 0.05-0.50" of rain. Temps change little for the
rest of the day with the clouds hanging tough.

Prev...
Clouds continue to increase, lower and thicken this morning from
west to east with light rain breaking out over much of the
Alleghenies here in the predawn hours. The approaching sfc
frontal system is running into CAD in place over Central PA
so eastward progression of precip will continue to be a chore.
Still, moisture transport aloft is continuous this morning and
will win out, with light rain/showers eventually spreading
through the most of central PA through mid morning. It should
then be showery throughout from the late morning through late
afternoon hours with a rumble or two of thunder possible thanks
to some elevated instability. but there might be a thunderstorm
or two, more probable in the SW than E. Temps on Monday won`t
go more than 10F above the morning numbers, and highs will range
from the low to mid 60s in most areas, but perhaps near 70F
across the Lower Susq Valley.

&&

.SHORT TERM /7 PM THIS EVENING THROUGH TUESDAY NIGHT/...
First surge of light rain/showers peters out somewhat by this
evening with a relative lull in the activity seen for several
hours tonight. Another minor surge of WAA and moisture aloft
arrives in the Laurels before sunrise Tuesday with increasing
POPs again at that time. Given recent dryness, no flooding
concerns for tonight`s rainfall which should average from a
third to half inch in most basins. Cloudy and unsettled
conditions prevail through Tuesday evening with continued
rain/shower chances, especially central and western areas in
best proximity with frontal forcing. There can also be rumbles
of thunder from time to time, but not much beyond that.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Model guidance outlines another surface low-pressure system
tracking northeastward across the Great Lakes and into southern
Ontario on 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 overhead coupled with enhanced moisture, have
retained likely PoPs on Wednesday with highest chances during
the late morning to early afternoon hours. Heavy rainfall
threats look less robust compared to previous forecast cycles;
however, some instability will allow for thunderstorms across
the Laurels, brining some potential for locally heavy rainfall,
with maximum totals ~0.50" on Wed.

Lingering showers across mainly E PA will continue into
Thursday before a brief reprieve in rainfall Thursday evening
and into Friday morning. Rainfall chances begin to increase as
Friday morning progresses with the potential remnants of PTC9
approaching the area. There is still some uncertainty in regards
to how PTC9 will impact central Pennsylvania, mainly dependent
on interactions with a trough stationed across the eastern
Tennessee Valley. At this time, deterministic model guidance
shows modest agreement in the bulk of rainfall keeping south of
the area; however, given uncertainty have not deviated much from
NBM guidance this cycle. If precipitation manages to make way
into central Pennsylvania in the Friday-Sunday timeframe,
highest chances (25-35%) will be across S/W PA along the Laurels
with a SChc (15-25%) progged west of the Susquehanna Valley.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
MVFR-to-IFR conditions are generally expected over the next 24
hours across central Pennsylvania, although some scattering out
of the lower-level cloud deck possible across the Laurel
Highlands (JST/AOO) in the near-term (through 20Z) portion of
the TAF package. As the evening progresses into the overnight
period, there is moderate-to-high (60-70%) confidence in
prevailing IFR conditions across much of the area. Low-level
cloud decks ~300ft AGL are expected to impact all of the western
airfields (all minus MDT/LNS) with moderate (~60%) confidence
in the 03-13Z timeframe, with slight differences in
onset/lifting of restrictions. After sunset, expect western
airfields to prevail IFR through 18Z Tuesday, although there is
slightly lower confidence in the 15-18Z Tuesday timeframe.

For the LSV airfields (MDT/LNS), there is some uncertainty with
regards to the eastward extent of low-level ceilings impacting
the airfields after 22Z Monday. At this time, the bulk of model
guidance suggest MDT is more likely to experience restrictions
with HREF guidance pushing towards 40-50% probabilities in IFR
ceilings throughout the overnight period, thus have slightly
higher confidence in IFR conditions prevailing. At LNS, slightly
lower probabilities and a combination of GLAMP/RAP model
guidance outlines low-end MVFR as the more likely outcome after
22Z Monday; however, ceilings/visibilities will be very
borderline in the 06-13Z timeframe. At this time, have outlined
MVFR ceilings given lower probs of IFR ceilings and sticking
closer to GLAMP guidance given uncertainty.

Outlook...

Wed...Chc/Likely SHRA with some TSRA possible.

Thu...Lingering/scattered showers possible E PA.

Fri-Sat...Scattered SHRA S/W PA; otherwise, trending drier.

&&

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

&&

$$

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