229
FXUS61 KCTP 230931
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
531 AM 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 6 PM THIS EVENING/...
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 /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
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 /TUESDAY NIGHT THROUGH SUNDAY/...
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 systemoverhead co
coupled with enhanced moisture, have retained likely PoPs in the
Tuesday to Wednesday timeframe. Given PWATs in the 1.25-1.75"
range on Wednesday, locally heavy rainfall will be possible with
relatively slower storm motion also possible. This threat has
been outlined with marginal (level 1/4) risks in the D3 (area
wide) and D4 (SE 1/2) Excessive Rainfall Outlooks from the
Weather Prediction Center. Highest impacts are expected to be
across areas that have recently received heavy rainfall, such as
urban areas of the Lower Susquehanna Valley, along with hydro
sensitive areas across the northern tier.

Model uncertainty in previous packages still remain late
Wednesday/early Thursday and into the end of the long-term
period, so there is low confidence as we move past Thursday
morning on this forecast cycle. A (potentially) slower
progression of the departing low- pressure system retains
chances through Thursday, with slightly lower chances as we move
into Friday.

The remnants of a tropical cyclone could also bring about rain
chances this weekend, but uncertainty with respect to
interactions with a trough that could limit chances of
precipitation/increase chances as we get closer to an event.

At this time range, have maintained numbers close to NBM
guidance which continues to paints SChc PoPs (~15-25%) or below
across the western PA with some enhancement of precipitation
along the Laurels.

&&

.AVIATION /10Z MONDAY THROUGH FRIDAY/...
06Z TAFS sent.

Not a lot of change from the earlier TAF package. Band of
showers coming in a bit faster. The rain will tend to lower
conditions during the day, but time of day will tend to offset
the lower conditions a bit. By sunset I would expect conditions
to lower again.

The main feature on the weather map early this morning is a
weak low over western Lake Erie. Trend for the next few days is
for the frontal system to remain near the area. Thus I would
expect similar conditions each day for most of the week. While
VFR conditions may occur at times, I would expect this to be
for brief periods of time.

Outlook...

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

Thu...Lingering/scattered showers possible area wide.

Fri...Scattered SHRA SW PA; otherwise, trending drier.

&&

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

&&

$$

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