542
FXUS61 KCTP 221043
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
643 AM EDT Wed May 22 2024

.SYNOPSIS...
*Summerlike warmth+humidity to fuel risk of severe t-storms
 this afternoon and evening; damaging winds primary threat
*Showers & t-storms continue Thursday especially over south
 central PA; strong storm possible in the Lower Susq Valley
*Rain chances trend lower into Friday before increasing over
 Memorial Day weekend

&&

.NEAR TERM /THROUGH TONIGHT/...
Some patchy valley fog to start today; otherwise abundant
sunshine this morning will send temps into the 80s in most
locations by 12-1PM. An increasing southwest flow ahead of an
upstream cold front will advect noticeably more humid air into
the area with dewpoints in the low to mid 60s. It will feel like
summer: very warm and sticky with max temperature range 80-90F
or +10-15 degrees above late May climo/approaching daily record
highs in some locations (see climate section).

Overall, not much change in the near term fcst/severe t-storm
risk for later today. SPC did expand the SLGT risk area (level
2 out of 5) a little farther to the east to I81 and added a 2-4%
tornado prob to the south of Lake Erie where the "best" deep-
layer shear will exist. The 22/00Z HREF shows t-storm clusters
developing during the afternoon and progressing eastward through
the evening within corridor of moderate instability near a
leading prefrontal trough. 0-6km shear decreases with eastern
extent across the CWA which remains somewhat of a limiting
factor concerning the overall severe potential. However, mean
MLCAPE in the 1000-1500 J/kg range along with steep lapse rates
will support isolated damaging wind and hail threats. T-storm
intensity and coverage should diminish into tonight as the best
forcing/height falls lift to the north and low level stability
increases with the loss of daytime heating.

A lull or relative minimum in the shower/t-storm activity is
expected overnight. However, will maintain lower POPs into
Thursday morning associated with the arrival of a weakening cold
front. Patchy fog is possible again especially in areas that
receive rainfall particularly if cloud breaks help promote
more efficient radiational cooling. Lows in the 60s are rather
mild for this time of year or +15-20 degrees above the
historical climate average.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
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.

Rain chances trend lower from north to south into Friday as
upper level ridging builds over the area. Max POPs 30-40% are
over the southern tier of CPA near stalled/pivoting q-stnry
front and axis of highest pwats. The front lifts back to the
north as a warm front Friday night with showers likely by
Saturday morning over the western Alleghenies.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
A round of convection is forecast into Saturday 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 /12Z WEDNESDAY THROUGH SUNDAY/...
Mainly clear skies will begin the day across central PA today.
Very little fog developed overnight, and temperatures are
beginning to heat up in the morning sunlight.

Height falls ahead of an approaching cold front bringing
convection to the region today with strong storms possible. The
best timing of showers and storms will be after 18Z today.
These showers could last through the late evening and into the
early morning hours on Thursday as the cold front finally passes
through and then stalls out south of PA. A few of these storms
could be locally severe with wind gusts being the main threat.

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

Outlook...

Thu...Chance of t-storms.

Fri-Mon...Mainly VFR, but chance of showers/AM patchy fog.

&&

.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/Steinbugl
SHORT TERM...Fitzgerald/Steinbugl/Banghoff
LONG TERM...Fitzgerald
AVIATION...Bowen
CLIMATE...Steinbugl