072
FXUS61 KCTP 251629
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1229 PM EDT Sat May 25 2024

.SYNOPSIS...
A shortwave passing north of the region will push a weak cold
front through the state Saturday night. Low pressure will then
track west of Pennsylvania Sunday night into Memorial Day, with
the trailing cold/occluded front coming through Monday evening.
An upper level trough will build into the region for the
remaining portion of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
A line of storms is making its way into northwest PA at noon
and will continue to drift east/southeast this afternoon
associated with a surface trough beneath a couple of vort
maxes/shortwaves aloft. Plenty of diurnal heating and the
advection of warmer and moist air will support MLCAPEs near 1500
J/kg this afternoon across the west and south- central
mountains and help direct storms southeastward. RAP forecast
soundings depict mid-level elongation with very weak low-level
winds. As such, marginally severe hail is expected and a couple
of 1" hail stones are possible. The stronger cores may also
produce gusty to locally-damaging winds.

Have already seen a couple cells try to get going ahead of the
main forcing in southwest PA, and would not be surprised to see
additional activity there through the afternoon. The main
broken line of storms is progged to affect JST/UNV/IPT late this
afternoon/early this evening and then clear our forecast area
before midnight. With storms moving at 20kts or so, the threat
for heavy rain/minor flooding is not too high, but worth the
MRGL risk ERO from WPC, especially for locations that receive
multiple rounds of showers. Temps this afternoon will be
similar to the past few days with u70s-m80s at the max.

Ongoing convection should drop SE in the early evening, and
drier air will move in for the overnight as a cold front pushes
across. The front will likely be behind the forcing and not make
more than an isold SHRA or two as it passes. Have kept PoPs
below mentionable for the second half of the night. The
clearing and rain earlier in the day/evening will likely lead to
fog forming over a good portion of the CWA tonight. Dewpoints
don`t dip much at all. Mins of 60-65F in the SE half and 55-60F
in the NW half are a little milder than normal. Not much wind at
all in the morning, so it may take 2-3hrs after sunrise before
all the fog goes away.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY/...
As the fog lifts on Sunday and the front tries to return
northward, there will be a smattering (30-40pct coverage) of
SHRA/TSRA pop up in the aftn. These will be most numerous over
the higher elevs of the SC mtns and Poconos. But, a couple could
drift into the urban areas of the Lower Susq. Not many should
form N of IPT. The pulse cells should pose very little threat
for svr wx, but CAPEs into the 1500-2500J range will be enough
to make a strong gust or two. The rest of the area will be dry
and mostly sunny. Temps will be a repeat.

All guidance tracks a seasonably strong surface low northeast
across the Grt Lks Sunday night into Monday, with a trailing
cold/occluded front likely coming through Central PA Monday
night. Falling heights/upper level diffluence ahead of the
associated upper trough, combined with surging pwats along the
attendant low level jet, should result in numerous showers/tsra
late Sunday night through Memorial Day. Ensemble median rainfall
during this time period is 0.50-1.00 inches, representing the
most likely areal averages. However, embedded tsra should result
in locally heavier amounts and potentially an isolated flood
threat.

Current guidance indicates the best chance of severe weather
will be in the warm sector across Western PA Mon PM. The latest
NAM and GEFS hint at a triple point low passing south of Central
PA, with lingering low clouds/southeast flow north of this
feature keeping Central PA cooler and less prone to severe wx.
However, we`re still several days out and the mid level flow and
deep layer shear looks fairly impressive. EPS CAPE plumes over
Central PA Mon PM are widely dispersed, ranging from <300 J/kg
to almost 2000 J/kg if the warm front lifts east of the
Appalachians.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Medium range guidance all points to a period of cool weather
later next week, as a deep upper level trough pivots southeast
from the Grt Lks. The cold temps aloft should support a daily
chance of diurnally-driven showers, with the highest POPs across
the elevated heat source of the Allegheny Plateau. The best
chance of showers and isolated tsra overall should come with
the passage of a strong shortwave Wednesday. Both the GEFS and
EPS signal drier and warmer weather late next week, as the upper
trough shifts east of PA.

&&

.AVIATION /16Z SATURDAY THROUGH WEDNESDAY/...
Widespread VFR conds are expected to continue with high
confidence (> 80%) through 20Z Saturday. After 20Z, scattered
showers and thunderstorms are expected to develop and could
cause brief restrictions. Timing has trended ever so slightly
later in the afternoon and have adjusted timing slightly to
reflect updated guidance. Some uncertainty remains with
coverage, but higher confidence at western airfields (UNV and
points west) in TSRA/SHRA reaching airfields. There is some
potential for localized restrictions with the strongest showers
and thunderstorms, but confidence is too low (< 30%) to mention
in the 12Z TAF package.

After rainfall ends late Saturday evening and into early Monday
morning, the bulk of model guidance suggests vsbys (and to a
lower degree cigs) dropping towards IFR/LIFR thresholds. Given
rainfall this evening, an increase in low-level moisture,
light/calm winds, generally expect these thresholds to be met
especially if any breaks in the clouds manage to form.

Outlook...

Sun...Patchy AM fog, otherwise predominantly VFR outside of a
stray aftn shower.

Sun night-Mon...Restrictions possible with SHRA/TSRA
developing.

Tue-Wed...Scattered SHRA possible.

&&

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

&&

$$

SYNOPSIS...Fitzgerald
NEAR TERM...Dangelo/Banghoff
SHORT TERM...Dangelo/Banghoff
LONG TERM...Fitzgerald/Banghoff
AVIATION...NPB