314
FXUS61 KCTP 220009
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
809 PM EDT Tue May 21 2024

.SYNOPSIS...
*Surge of summerlike warmth and humidity through midweek
*Strong to severe t-storms possible Wednesday afternoon
*Seasonably warm & unsettled Thursday through Memorial Day

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Low level convergence combined with the approach of a mid level
vort max over Northern W Virginia is supporting a few isolated
showers early this evening along the spine of the Alleghenies
along the Somerset/Bedford County border. Expect this activity
to diminish as the sun sets and boundary layer cools.

High pressure centered just off of the Mid Atlantic coast should
then support fair and warm conditions for Central PA the rest of
the night. Any lingering cumulus over the Allegheny Plateau
should collapse around sunset, with mainly clear skies for the
balance of the night. The gradual advection of higher dewpoints
through daybreak Wednesday, along with clear skies, may result
in patchy valley fog late tonight. Highest fog potential based
on SREF and NAMNest is across the south-central part of the
forecast area around Bedford/Fulton counties and in the deep
river/stream valleys from Elk to Northern Clinton counties. See
no reason to deviate significantly from NBM min temps, which
range from the upper 50s to low 60s.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
Model guidance indicates a decent mid level shortwave will track
across the Lower Grt Lks Wed PM. Modest height falls and surging
pwats ahead of this feature will result in developing afternoon
convection across the region. Latest SPC outlook places the
northwest half of the CWA in a slight risk of severe weather
associated with decent mid level flow/deep layer shear near the
path of the shortwave. A marginal risk extends into the
southeast counties, where less impressive kinematic fields are
noted in the model guidance.

Latest HREF shows t-storm clusters developing ahead of an
eastward advancing cold front/near a leading pre frontal trough
and moving west to east across the area from around midday
through the late evening. Isolated strong to severe wind gusts
are the primary threat. However, cape in the 1000-1500J/kg and
steep lapse rates could also support isolated large hail. The
severe weather threat will diminish by late Wed evening, as the
shortwave passes north of the area and instability wanes.

Model 850mb temps near 16C support high temps Wednesday in the
80s. An increasing southwest flow ahead of an upstream cold
front will advect increasingly humid air into the area, with
dewpoints in the low to mid 60s.

A break in the shower/storm activity is expected late Wednesday
night, as the shortwave and best large scale forcing passes
north of the state. However, will maintain low POPs into
Thursday morning associated with the arrival of a weakening
cold front. By daybreak Thursday, some patchy fog is possible,
especially if any breaks in the clouds help promote more
efficient radiational cooling.

More showers and t-storms are likely Thursday, primarily during
the afternoon, as the cold front stalls out near the Mason
Dixon Line and a shortwave rolls eastward from the Ohio Valley.
The focus for convection Thursday will be over the southern
part of the state. However, model RH profiles support a good
deal of high level cloudiness extending into Northern PA, which
should hold temps down. Expected high temps range from the mid
70s to low 80s, but remain above climo for this time of year.
Low temps Thursday night/AM Friday in the 55-65F range will not
be as warm/humid as Wednesday night.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Looking at above normal temperatures into the holiday weekend.

The proximity of a frontal boundary to the south and west of
PA into at least early next week, will keep some chance of a
shower and perhaps a storm across the region from time to time
through Monday. Highest chance will be across the far south and
far west.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
A few CU forming as of 1 PM across the ridge tops. While
dewpoints not real high and the airmass aloft rather warm,
intense afternoon heating could form a shower or storm across
the higher terrain in spots like BFD and perhaps JST.

Otherwise just looking at mainly a few clouds into late morning
on Wednesday. Have a TEMPO for fog in at MDT and LNS, but less
chance than during the past few mornings. Main thing going for
a bit of fog in the far southeast will be rather light wind
fields.

Timing of showers and storms with the cold front late Wednesday
into early Thursday will be after 18Z. Did have a VCSH in at
BFD after 17Z.

Conditions may dry out for Thursday, but the nearby frontal
system may keep some showers nearby into the holiday weekend.

Outlook...

Thu...Chance of t-storms.

Fri-Sun...Mainly VFR, but chance of showers.

&&

.CLIMATE...
Daily record maximum temperatures for 5/22:

Harrisburg96/1941
Williamsport95/1941
Altoona88/2013
Bradford84/2013
State College89/1975

&&

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

&&

$$

SYNOPSIS...Steinbugl
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald/Banghoff
LONG TERM...Martin
AVIATION...Martin
CLIMATE...Steinbugl