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881
FXUS61 KCTP 231907
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
307 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 /THROUGH TONIGHT/...
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Just a few breaks in the clouds have opened over the Laurels
and Warren Co this aftn. We shouldn`t see this improvement
spread much farther eastward since the flow is still E/SE in
llvls and continues to be highly influential. Despite the
building ridge aloft, the clouds should spread back to the west
and reclaim their previously held territories. The clouds will
keep the temps from going more than 5-10F lower than current
values. PoPs will be in the 30-60pct range for most, mainly kept
lower than categorical because the precip will be very light
and disorganized.
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&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
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Good surge of moisture and forcing comes across the CWA in the
afternoon and evening Tuesday. Some instability will be present
in the west, so the slight chc T will be retained there. SPC
even touches Somerset Co with a MRGL risk of svr wx. Similarly,
the ERO is also a MRGL risk - and only in Somerset Co. The
showers/thunder should really not be enough to drop enough
rainfall to generate flooding there since it has been so dry.
The rain today (Mon) was barely enough to get water to the
soils. Maxes will be just 5--8F above nighttime lows. Any
breaks in the clouds in the AM will close up.

Tues night is mainly rain, Basin averages thru the next 36 hrs
will be 0.25-1", and will be welcome rainfall in many areas.
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&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
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 /19Z 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...Dangelo
SHORT TERM...Dangelo
LONG TERM...NPB
AVIATION...NPB