684
FXUS61 KCTP 040136
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
936 PM EDT Fri May 3 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 SATURDAY/...
Radar loop at 0130Z shows dwindling, diurnally-driven
convection moving into the western part of the forecast area, as
it encounters a more stable air mass over the Allegheny
Plateau. Expect this trend to continue into the evening hours,
with a lingering chance of a shower over the Alleghenies.

The focus later tonight 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 /SATURDAY NIGHT 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/...
The long term period will be dominated by WSW flow aloft. Sfc
boundaries linger overhead/nearby the state for the entire
period. Several successive shots of shortwaves should slide
overhead, likely the remnants of a very active/stormy time over
the central plains. Thankfully, the expected severe weather in
the middle of the country is not expected to extend this far to
the east on most (if any of the) days. However, we do get the
forcing provided by the repeated MCSs. These things are highly
difficult to track and anticipate the timing of arrival, too,
4-7 days out. The ECMWF does push the boundary south of PA
enough for Tues to be dry. But...the GFS and importantly, the
blend of models, never let go of 30-80 PoPs. Gulf moisture
really never gets totally cut off from reaching the OH
Valley/Mid-Atlantic States, but does diminish somewhere in the
vicinity of PA. Thus, there is high confidence of a wet period
during the entire long term, esp for srn PA, but extremely low
confidence in timing of each successive wave. PoPs >30pct will
remain for each 12hr period, as there is no model or conceptual
consensus to dip that low. They also won`t go above 80 pct for
much the same reason.

&&

.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
Scattered SHRA across western PA has largely stayed east of all
airfields in central PA. Some light SHRA passed over JST/AOO
although relatively dry air in the lower-levels made for very
little in the way of rainfall. Some light showers are still in
the vicinity so have outlined VCSH for these airfields for the
next couple of hours. The best chance of SHRA at either airfield
will come in the very near-term (00Z-01Z) although showers
continue to break apart. Chances of TSRA are low (< 30%) and
have kept them out of the TAFs for this cycle, with any TSRA
occurring at BFD/JST. Chances for TSRA after 03Z Saturday drop
even further with the loss of daytime heating.

Chances for low clouds and some fog do remain possible, although
model sounding shave outlined less moisture in the lower-levels
that would promote fog formation. If any fog formation is to
occur, best chances will be across SW PA at JST with lesser
chances at AOO. Southeasterly winds will increase probability
of fog in these locations as well, but with low confidence have
opted to keep fog out of this TAF package.

Light SHRA will continue on Saturday with restrictions expected
at all airfields across central PA. Widespread MVFR conds are
expected by 12Z Saturday with IFR cigs expected across Allegheny
Front airfields (JST/AOO/UNV, lesser IPT) throughout the day on
Saturday.

Outlook...

Sun...Widespread restrictions due to low cigs. SHRA likely with
a chance of TSRA.

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...Dangelo
AVIATION...NPB