-- Discussion containing changed information from previous version are highlighted. --
039
FXUS61 KCTP 220533
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
133 AM EDT Wed May 22 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 THIS MORNING/...
High pressure centered just off of the Mid Atlantic coast
will bring fair and warm conditions to Central PA the rest of
the night. Mostly clear skies and light winds may result in
patchy valley fog late tonight. The 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 THIS MORNING THROUGH THURSDAY NIGHT/...
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.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Drier and warm weather is anticipated Friday, as upper level
ridging builds over the area. However, a stalled frontal
boundary over Southern PA will be the focus for scattered PM
convection over that part of the state.

Low pressure lifting through the Grt Lks will likely produce a
round of showers associated with the attendant warm front Friday
night, followed by a round of convection with the trailing
cold/occluded front Sat afternoon. Current model guidance
supports a period of dry weather late Saturday into Sunday
associated with a weak surface high building across the Lower
Grt Lks into PA.

A deepening upstream trough will then likely result in a period
of wet weather Sunday night into Monday, as the associated
surface low tracks just west of PA. Medium range guidance
currently indicates the severe weather risk is low due to the
warm front hanging up west of the Appalachians. However,
ensemble plumes support a decent rainfall in the 0.5 to 0.75
inch range between Sunday night and Monday night. The deepening
upper level trough is progged to push into the region Tuesday,
marking a transition to cool weather with scattered, diurnally-
driven convection possible.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
Calm and mainly clear overnight tonight. A few high clouds
will be overhead by early morning. There is 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.

A cold front will come through Wednesday afternoon bringing
convection to the region with strong storms possible. The best timing
of showers and storms with the cold front will be after 18Z
Wednesday. These showers could last through the late evening and
into the early morning hours on Thursday. A few of these storms
could be locally severe.

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.
-- End Changed Discussion --

&&

.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...Fitzgerald
AVIATION...Bowen
CLIMATE...Steinbugl