213
FXUS61 KCTP 040653
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
253 AM EDT Sat May 4 2024

.SYNOPSIS...
-Noticeable cool down over the weekend with overcast skies and
 periods of rain
-Remaining unsettled next week with a gradual warming trend

&&

.NEAR TERM /THROUGH TODAY/...
Radar loop at 03Z shows dwindling, diurnally-driven convection
over the NW Mtns. The focus for the rest of the night shifts to
the potential of additional showers linked to a mid level vort
max lifting into Southwest PA from the Ohio Valley. Surging
pwats, combined with the arrival of this feature will bring an
increased chance of showers over primarily the southwest portion
of the forecast area late tonight.

An increasingly moist east/southeast flow off of the Atlantic,
combined with upslope flow, will likely yield developing
stratus along the spine of the Appalachians late tonight. Low
temps will be above early May climo and range between 45-55F
from the southwestern Poconos/Coal Region to Warren County.

&&

.SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/...
Model guidance supports developing rain Saturday across Central
PA from south to north ahead of an upper level shortwave
lifting out of the Tennessee Valley. The associated southerly
low level jet and plume of higher pwats overrunning a dome of
cool/stable air across Central PA should result scattered
showers giving way to a steady rain early Sat morning over the
southern tier counties and by late in the day over the northern
tier. The upper level shortwave should begin to lift out of the
area Sunday, resulting in rain tapering off from west to east.
Scattered late day convection appears possible late Sunday over
the Allegheny Plateaus associated with an approaching warm front
over Western PA. Ensemble plumes support rain totals by late
Sunday in the 0.5 to 0.75 inch range for most of the area.

Hires models show CAD pattern firmly entrenched over CPA Saturday,
and therefore we continued to trim max temps vs. NBM, due to
thick cloud cover, easterly flow and arriving rain. We have
blended the cooler NAM surface temps with those of the NBM,
resulting in expected max temps in the mid to low 50s for much
of the area. No risk of thunder on Saturday, so removed from wx
grids and changed character of precip to rain from showers.

Sunday looks to be another cool day for May, due to a persistent
southeast flow off of the Atlantic. However, a slight rebound
is expected over the western counties, due to rain tapering off
the chance for a bit of afternoon brightening.

Subsidence behind the departing shortwave should result in a
mainly rain-free Sunday night. However, a lingering upsloping
southeast flow will likely yield lingering low clouds/patchy
drizzle. Fcst lows Sunday night are +10-15F above climo for
early May in the 50-60F range.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Monday should feature much warmer and drier weather, as high
pressure builds southeast from the Grt Lks behind a Sunday night
cold/occluded front passage. However, the approach of an upper
level shortwave appears likely to produce scattered PM
convection in the vicinity of the stalled front along the Mason
Dixon Line. Highest POPs are placed over the southern tier,
with only slight chc POPs across the north. The return of
sunshine and 850mb temps near 12C translates to expected highs
in the 70s most places.

Upper level ridging over PA indicates warm and generally dry
conditions are likely Tuesday. However, a warm front lifting out
of the Ohio Valley could result in increasing clouds with a PM
shower/tsra, primarily across the southwest counties. The bulk
of medium range guidance supports a very warm Wednesday with
scattered convection, as the area briefly breaks into the warm
sector ahead of a cold front pushing in from the Grt Lks.

Model consensus supports a better chance for a more widespread
rainfall Thursday, associated with a deepening upstream trough
and wave of low pressure riding along the stalled cold front
just south of PA. The surface low and deepest moisture is
progged to shift east of the area by Thursday night. However,
falling heights ahead of the upper trough will likely support
scattered, diurnally-driven convection Friday, along with a
downward trend in temperatures.

&&

.AVIATION /07Z SATURDAY THROUGH WEDNESDAY/...
As of 0630 UTC Sat, MVFR cigs have moved into the Laurels (JST
and AOO) as well as portions of south central PA (CXY and THV).
The low cigs will continue to expand over the next several
hours, with the remaining TAF sites likely dropping to MVFR or
lower by daybreak. Confidence in MVFR cigs after 11z is lowest
at LNS, where much of the hires guidance shows LNS on the
eastern periphery of the MVFR cloud deck.

IFR conds are likely to develop first across the western
airfields (BFD, JST, and AOO between 10z and 15z Sat) and then
expand eastward through the day. Confidence is low in the exact
timing of the low cigs. Periods of light rain will continue
through the day.

Southeast winds of 5-15 kts will continue through the TAF
period, with gusts up to 25 kts. LLWS may become a concern from
00z-18z Sun as a southerly LLJ develops with 2kft winds 35-45
kts, strongest through north central PA. The LLJ will also
produce the most widespread and heaviest rainfall during this
period.

Outlook...

Sun...Widespread restrictions due to low cigs. SHRA likely with
a slight chance of TSRA. Areas of fog poss Sun night.

Mon-Wed...AM fog/clouds poss. PM -SHRA possible areawide.

&&

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

&&

$$

SYNOPSIS...Steinbugl/Bowen
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald/Bowen
LONG TERM...Fitzgerald
AVIATION...Colbert/NPB