097
FXUS61 KCTP 231907
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
307 PM EDT Thu May 23 2024

.SYNOPSIS...
A front will remain just south of the Commonwealth tonight and
Friday, while a ridge of high pressure slides east across the
state bringing a couple of nice days with dry conditions and
comfortably low humidity. More clouds and an uptick in humidity
will arrive for Saturday and persist through Memorial day with
a period or two of showers and possible thunderstorms, mainly on
Saturday and again Sunday night into Monday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Drier air continues to work into northern and central portions
of central PA as a cold front becomes stationary dropping south
of the Mason Dixon line by this evening. Sfc dewpoints have
dropped through the 50s and into the 40s over the NW Mountains,
and into the lower 60s over the central mountains with partial
clearing over a large portion of central and even south central
PA.

Isold shra and a rogue tsra are possible over the southern third
of central PA this afternoon INVOF the stalling boundary to the
south, and where sfc dewpoints remain in the 60s with PW still
between 1.0 and 1.25". A shortwave traversing nrn VA and the the
panhandles of WV/MD may provide enough of a trigger for this
activity, but mass fields are marginal and do not expect any sig
sensible wx from any of this convection.

Some patchy fog will be possible tonight in areas that remain
clear, with clouds most prevalent across the south near the
stalled boundary. Mins will range from near 50 in the north to
the lower 60s over the southeast.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
Friday is looking like the best weather day of the weekend as a
weak bubble of high pressure keeps fair weather over most of
central PA. The aforementioned stationary front will tend to
lift northward as a warm front by Friday night with showers
likely by Saturday morning over the western Alleghenies. More
diurnally forced showers and storms will develop Saturday
afternoon with daytime heating and some enhancement with a
prefrontal trough. Saturday will not be a washout by any means,
but those with outdoor plans should monitor the weather and head
inside if you hear thunder.

Compared to Saturday, the chance for showers and thunderstorms
on Sunday will be lower, owing to a weak surface high building
across the Lower Grt Lks into PA. However, with a warm front
approaching, we do carry slight chance to chance PoPs Sun
afternoon. Highs will range from the upper 70s in the
Endless Mountains to the mid 80s through the Susquehanna Valley.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
The chance for rain will increase into Sunday night as a warm
front crosses through the region. According to the latest NBM
guidance, the wettest period looks to be from Sun night
through the first half of Mon night. Ensemble median rainfall
during this time period is 0.75-1.25 inches for much of the
area. The rain will likely come in batches, with the first batch
Sunday night, potentially a lull early Monday, and then heavy
showers and thunderstorms Monday afternoon, putting outdoor
Memorial Day activities at risk.

A longwave trough will then set up over the eastern US and
persist through much of the upcoming week, with several
shortwave troughs rotating through the base of the trough. With
850 mb temps only in the single digits, our highs on Tue-Thu
will be noticeably cooler, topping out in the 60s to low 70s.
Given the low level instability beneath the cold pool aloft, we
have moderate confidence in scattered diurnal showers and
isolated thundershowers Tue-Wed, with the highest PoPs in NW
zones (closer to the upper low). Models diverge in timing the
departure of the trough late in the week. PoPs are lower on Thu
as some ensemble members have high pressure building in.


&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Dry air at midlevels has translated to a dry afternoon across
central PA, despite the presence of some convective instability
and a cold front sagging southward through the area. Expect
VFR conds through the remainder of the day, with scattered
midlevel cu and increasing upper level cirrostratus. A few
isolated showers may pop up near the MD border during the
evening hours, where the cold front slows its southward advance
and taps into some deeper moisture.

Guidance continues to show the chance of low vsbys and cigs
late tonight into Friday morning, with recent GLAMP guidance
and RAP guidance suggesting JST may experience an extended
period of IFR/LIFR conditions. Given some uncertainty with
regards to extent, have kept IFR restrictions limited to JST
from 10z-14z, with MVFR conds at AOO and UNV.

Generally VFR conds will prevail on Friday.

Outlook...

Sat-Sun...Mainly VFR, but chance of showers (mainly Sat)

Sun PM - Mon PM...Restrictions possible with periods of
SHRA/TSRA

Tue...Scattered SHRA poss

&&

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

&&

$$

SYNOPSIS...Lambert/DeVoir
NEAR TERM...DeVoir
SHORT TERM...DeVoir
LONG TERM...Lambert/Colbert
AVIATION...Colbert/NPB