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000
FXUS61 KCTP 180320
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1120 PM EDT Wed Apr 17 2024

.SYNOPSIS...
-Unsettled with periods of showers through Friday
-Weekend cool down; monitoring frost/freeze risk Saturday-Monday

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Radar loop at 03Z shows a weakening band of convection over
Central PA in a region of falling heights and surging pwats
ahead of an upper low lifting into the Grt Lks.
Convection-allowing models, which are performing well in this
strongly-forced scenario, indicate most of the showers will have
cleared the eastern part of the forecast area by around 07Z.

An occluded front over Western PA is progged to push into the
central mountains by dawn. A drier westerly flow in its wake is
likely to bring partial clearing to the western half of the
forecast area late tonight. To the east of this boundary,
abundant low level moisture and an upsloping southeast flow
should yield lingering low clouds and perhaps some ridgetop
fog/drizzle over the mountains north of KIPT and the Western
Poconos.

Low level cold advection will push temperatures slightly lower
overnight across the western half of the PA, while readings
remain nearly stationary under cloud cover across the east.
Readings at dawn should generally be in the low to mid 50s
area-wide.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
Improving conditions on the way for Thu thanks to rising
heights, as the remnants of the upper low pass well north of PA
and deep layer moisture exit to the east. Residual low level
moisture combined with upslope flow should support lingering
drizzle over the mountains north of KIPT and the Western
Poconos, where model sfc-850mb RH fields are near 100pct. Also,
a weak shortwave diving southeast into the region could support
an isolated shower in the vicinity of the stalled occluded
front, which models indicate will bisect the state from north to
south. Forecast soundings indicate the atmosphere will be
capped for afternoon showers across the western half of the
state.

Most model guidance indicates a closed upper low will pass north
of the region Friday, with a trailing occluded front coming
through Central PA Friday afternoon/evening. The triple point
low is progged to pass south of the forecast area, so the severe
weather threat looks very low. A decent plume of moisture with
pwats close to +2SD should support POPs close to 100pct and some
heavier showers. However, the best large scale forcing as
inferred by model 300-500mb qvec convergence fields passes well
north of PA, so expect overall rainfall to be less than
impressive. Latest plumes support amounts between 0.1 and 0.2
inches in general.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
The bulk of model guidance supports dry conditions Saturday
through through Tuesday morning as high pressure builds into
the area. Upper-level troughing does support below-average
temperatures for the majority of the period.

The combination of light winds, dry air, and mostly clear skies
associated with the surface ridge is likely to result in areas
of frost Saturday and Sunday nights. The greatest risk of frost
is over the northern mountains where the growing season is not
active, but areas in the growing season further south could also
be affected.

Temperatures are expected to moderate by Tuesday with the
surface high pressure shifting eastward off the east coast and
an approaching shortwave brings the next chance of showers.
Ensemble plumes indicate the best chance for precipitation will
come Tuesday PM.

&&

.AVIATION /03Z THURSDAY THROUGH MONDAY/...
Late evening update.

Weakening line of showers and thunderstorms. Added thunder to
UNV, AOO, and IPT. Outflow boundary just ahead of the line, so
expect line to continue to weaken.

Earlier discussion below.

Strong to severe storms over far western PA early this evening
will continue to work eastward into our area this evening. The
airmass is cooler and more stable in our area, and with the sun
setting, expect storms to weaken with time. Did mention thunder
at BFD and JST, may add to other sites later, if the activity
can hold together that far east.

Southeast sites now seeing lower CIGS given the southeast flow.

Overall expect lower conditions to linger into Thursday, as the
front slows down. Some improvement later in the day.

Another round of showers expected on Friday, with lower
conditions again.

Outlook...

Fri...CFROPA. Ocnl dips to IFR.

Sat...Light SHRA N, no sig wx elsewhere.

Sun-Mon...No sig wx.

&&

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

&&

$$

SYNOPSIS...Steinbugl
NEAR TERM...Fitzgerald
SHORT TERM...DeVoir/Fitzgerald/Steinbugl
LONG TERM...Fitzgerald/NPB
AVIATION...Martin