-- Discussion containing changed information from previous version are highlighted. --
743
FXUS61 KCTP 240302
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1102 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 8 AM TUESDAY MORNING/...
A moist llvl easterly flow will continue to sock in widespread
stratus and ridge-shrouding fog overnight through the mid
morning hours Tuesday across the bulk of the CWA east of the
Alleghenies.

Recently issued a Dense Fog Advisory for Schuylkill Cty, focused
on the I-81 corridor that runs along the highest terrain of the
county and experiences the greatest, orthogonal upslope
component to the wind in this setup. Vsbys in some places along
the stretch of I-81 from near Delano to Hegins will be near
zero.

Otherwise, look for generally scattered showers and areas of
drizzle amounting to less than 0.10 of an inch overnight as a
deep layer of mid level dry air spreads east over the
aforementioned moist low-level environment.

Temps will only fall by 1-3 deg F overnight, given the current
0-3 deg F T/Td spread. Lows will be between 55 and 60F.

&&

.SHORT TERM /8 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
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.

&&

.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 /03Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
The combination of a moist southeast flow off of the Atlantic
Ocean and a stalled warm front near the PA/OH border will
result in persistent stratus and patchy drizzle across Central
PA through Tuesday. The approach of an upper level disturbance
will spread additional showers into Western PA late Tuesday.

Upsloping flow should yield the lowest cigs along the spine of
the Appalachians tonight and Tuesday, where LIFR/IFR cigs are
very likely based on current conditions and model output.
Further east, the cigs are expected to be borderline IFR/MVFR at
KIPT and trending to MVFR at KMDT/KLNS after tempo IFR
conditions this evening.

Outlook...

Wed...Low cigs/showers likely. Improving conditions possible W
Mtns Wed PM.

Thu...AM low cigs/showers likely.

Fri...No sig wx expected.

Sat...Chance of low cigs/rain Laurel Highlands.
-- End Changed Discussion --

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 8 AM EDT Tuesday for PAZ058.

&&

$$

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