900
FXUS61 KCTP 290923
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
523 AM EDT Wed May 29 2024

.SYNOPSIS...
*Numerous showers/t-storms expected this afternoon->evening
*Drying trend to end May with below normal temperatures
*Seasonal warmup to start June with rain risk increasing into
 early next week

&&

.NEAR TERM /THROUGH TONIGHT/...
Issued SPS for areas of fog/low visibility (1/2-1/4 mile) and
locally hazardous driving conditions early this morning over the
western/northern Alleghenies. Expect fog impacts to end by 9AM.

Shortwave trough will pivot eastward from the upper Ohio
Valley this morning, eventually moving through central PA this
afternoon and evening before exiting the northern Mid Atlantic
coast tonight. 500mb height falls and abnormally cool temps
aloft associated with the aforementioned trough will provide
large scale lift and a period of steep lapse rates within a zone
of modest instability to produce scattered to numerous diurnally
enhanced showers and t-storms. A couple of repeat heavy
downpours could produce local QPF maxes around 1" as they
maneuver over the area into the evening, but the overall lack
of deep moisture (pwats<1") will greatly limit risk of heavy
rain/runoff issues. Max temps will be 5 to 10 degrees below late
May climo across most of CPA this afternoon with highs in the
60-75F range.

Shower activity shifts to the east tonight with patchy fog
possible over the western Alleghenies where skies should clear
out. Seasonably cool night ahead with lows in the 40-55F range.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
Final shortwave trough rotates through CPA on Thursday. A
couple of showers or an isolated PM t-storm are possible
Thursday afternoon beneath the upper trough axis mainly over
southeast PA, but lower pwat air pouring into the region via
NNW low level flow should keep most places dry. Highs will again
be cooler-than-average with fcst max temps in the low 60s/70s.

Seasonably strong high pressure dome migrates eastward from the
OH Valley Thursday night into western PA early Friday morning.
This setup should support one of the coolest nights in a while
with low temps in the mid 30s to upper 40s. Can`t rule out some
frost in the northern tier cold spots which is later than climo
but not that uncommon for the end of May.

Center of 1025mb sfc high is parked right overhead by 12Z
Saturday, ensuring the break in the rain continues into the
first weekend of June. Look for max temps to rebound a bit on
the last day of May with highs staying near/below climo. Another
relatively cool night with lows in the 40-50F range.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
Medium range models remain are in good agreement for an
extended stretch of dry weather through Sunday morning.
Temperatures moderate and humidity creeps up on Saturday and
Sunday. By Sunday, ensembles show upper level flow becoming more
zonal. Multiple shortwaves will move through the region into
the middle of next week bringing chances for showers and storms,
but confidence in the timing of these features is low.

&&

.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
VFR conds across SE PA are expected overnight with high (> 80%)
confidence while moderate (50-60%) confidence in VFR conds
continuing at AOO/IPT throughout the overnight period given the
low-level dry air at IPT as of 05Z Wednesday. There is higher
confidence on lower cigs forming at BFD/JST overnight with MVFR
cigs likely at both airfields after 09Z Wednesday. Guidance has
outlined some signals for a fairly rapid drop towards IFR at
JST/BFD in the 09Z-10Z Wednesday timeframe with HREF probs in
both MVFR/IFR cigs increasing significantly at JST in recent
runs. This seems plausible given lighter winds and clear skies
persisting this late into the evening, so have timed out best
possible timing for these restrictions. After sunrise, both
airfields are expected to lift towards high-end MVFR to low-end
VFR thresholds in the 13Z-15Z Wednesday timeframe.

Guidance has trended later with the approaching shortwave early
afternoon tomorrow with higher coverage of SHRA expected
throughout the day Wednesday. Rain is currently expected to
begin moving in from the west around 16Z and continue spreading
eastward into the afternoon. Brief visibility restrictions are
possible in any heavier showers and storms (see below), but
ceilings likely remain above VFR thresholds through 03Z. Sub-VFR
conds are possible across western airfields after 03Z Thursday.

As stated in previous discussions, elevated CAPE indicates
higher chances of TSRA as these showers progress across the area
today. This package outlines a fair window where TSRA is
possible at all airfields. In the next TAF package, expect to
tighten timing up where increasing confidence allows. At this
time, guidance does outline best chances of TSRA across the west
(BFD/JST/AOO) in the 20Z-22Z Wednesday timeframe with these
chances continuing towards eastern airfields (IPT/MDT/LNS) in
the 22Z-24Z Wednesday timeframe.

Outlook...

Wed Night-Sat...Predominantly VFR.

Sun...Showers and thunderstorms possible.

&&

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

&&

$$

SYNOPSIS...Steinbugl
NEAR TERM...Steinbugl
SHORT TERM...Steinbugl
LONG TERM...DeVoir/Bauco
AVIATION...Bauco/NPB