-- Discussion containing changed information from previous version are highlighted. --
151
FXUS61 KCTP 250725
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
325 AM 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 TODAY/...
-- Changed Discussion --
Probably just enough cloud cover to keep fog from forming in
more than just the far srn valleys this AM. Earlier storms near
MGW have dissipated. Next weather influencers are a pair of vort
maxes which will slide in from the NW. While difficult to
resolve the evolution of these features right now, their
presence will likely be the triggers for convection today. The
first should arrive later this morning and the second in the
middle of the aftn. CAPEs get up near 1000-1200J over the west
and south- central, with a minimum of 600-800 in the NE. Storm
mode may be supercells at first as the hodographs/helicity are
slightly favorable. 0-1km EHI gets above 1 in the far NW
(Warren/McKean Cos). LCLs in the NW are not too low. This will
help drive some good updrafts at the least and could allow for
an isolated tornado if the stars align in the NW. The wet bulb
zeroes are below 10kft and mid-lvl lapse rates are OK. So,
marginally severe hail is expected and a couple of 1" hail
stones are possible. The PWATs rise significantly (since we`re
very dry overhead at the moment) by noon in the west (near
1.25") and translate east thru the aftn/early evening. The
storms should be moving from 270 (early) to 290 (late) at
20-25KT as they pop up and cross the CWA. There will be some
isold/sct storms ahead of the main forcing, and we`ve put 20-30
PoPs in the SC-SE counties. There could be 2 shots (or more) of
rain for much of the area. Thus, the threat for heavy rain/minor
flooding is not too high, but worth the MRGL risk ERO from WPC.
Temps will be similar to the past few with u70s-m80s at the
max.
-- End Changed Discussion --

&&

.SHORT TERM /TONIGHT THROUGH MONDAY/...
-- Changed Discussion --
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 front
dsoesn`t go far and turns around on Sunday. 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.

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.

Prev...
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.
-- End Changed Discussion --

&&

.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 /06Z SATURDAY THROUGH WEDNESDAY/...
Widespread VFR conds are expected to continue with moderate-to-
high confidence (60-70%). Recent guidance takes out BR/FG
mentions at IPT/LNS, likely due to slightly less low-level
moisture, as seen on recent dewpoint depressions across the
region. Clear skies with calm/light winds will allow for some
fog potential across SW PA where there is slightly more moisture,
but generally expect these instances to be localized and away
from all terminals.

Any fog that does form will quickly dissipate after 12Z
Saturday with predominantly VFR conds throughout the early
afternoon hours. As the afternoon progresses, scattered showers
and thunderstorms are expected to develop and could cause brief
restrictions. Some uncertainty remains with regards to
coverage, but have began to time out any SHRA/TSRA mentions in
the 06Z TAF package. Conds are outlined to stay above MVFR
thresholds; however, localized heavier showers/storms could
bring about restrictions. After rainfall ends late Saturday
evening and into Monday morning, guidance hints towards
restrictions at BFD after 04Z Sunday and believe this is
plausible at this time with saturated grounds, light winds, and
some potential for breaks in clouds.

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
SHORT TERM...Dangelo
LONG TERM...Fitzgerald
AVIATION...Evanego/NPB