122
FXUS61 KCTP 050536
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
136 AM EDT Wed Jun 5 2024

.SYNOPSIS...
The ridge of high pressure at the surface and aloft that gave us
very warm and mainly dry weather across much of the state over
the past few days will weaken and move east of our area by
tomorrow.

A warm front lifting northeast across the Commonwealth on
Wednesday will make it more humid and bring an increasing
chance of showers and thunderstorms, some with heavy downpours
Wednesday into Thursday.

An upper level low will move to Southern Ontario and the Lower
Great Lakes for the Fri-Sun period with cooler conditions and
passing showers and storms each afternoon.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Varying amount of mainly mid-level/altocu and cirrus were
streaming ESE across the region this evening. The fairly sharp,
mid and upper level ridge overhead today and light SE to
Southerly flow brought temps mainly in the low to mid 80s with
upper 80s common across the Lower Susq Valley.

KBFD had somewhat low-hanging fruit and the old record high of
80 F (from way back in 1960) was smashed with a high of 84F.

Isolated to scattered light rain showers will drift across
Southwestern and Central PA overnight with QPF of only a few to
svrl hundredths of an inch.

PWAT Values ranging from 0.8 to 0.9 across the north, to nearly
1.5 inches in the far south will gradually climb overnight
making it feel rather muggy early Wednesday. Min temps around
daybreak will vary from near 60F across the highest terrain
north and east of KIPT to the mid 60s throughout the Central and
Southern Valleys or +10-15F above climo. Low stratus and patchy
fog will develop over the majority of CPA/east of the Allegheny
Front by daybreak.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY/...
Latest suite of hi-resolution guidance progresses a blossoming
area of showers across the CWA Wednesday morning through
Wednesday afternoon as a surface warm front lifts slowly NE
across the CWA.

Highest POPs will be occurring Wednesday night into early
Thursday morning when several rounds of showers and storms
appear likely. The best chance for severe weather should be
confined to northwest PA where the best combination of
ingredients exist, while farther southeast, persistent southeast
flow sets up a classic "cool" air damming scenario that should
limit instability for much of the day near and to the east of
the Susq Valley. The zone of question will be near an apparent
lee trough across Scent PA where the nose of a 35 KT southerly
LLJ will increase UVVEL and vert speed and directional shear
where the moisture is the juiciest.

This should be the focus for additional strong to potentially
SVR TSRA (with low LCL heights) late Wednesday afternoon and
evening. Wouldn`t be surprised to see SPC expand or paint a
small area of MRGL or SLGT risk for SVR across Scent PA.

Persistent low clouds and southeast wind favor cooler max temps
Wednesday (5-10 deg lower than today) with highs in the 70-80F
range.

The bigger threat with this system may end up being the
potential for heavy rainfall and some flash flooding. PWs climb
to 1.25-2.00 inches by 00Z Thu, which favors potential for
locally heavy rainfall. 12Z HREF paints some spot amounts of
2-3" in southern PA while the mean is closer to 0.75-1.5". WPC
upgraded the MRGL Excessive Rainfall outlook to a SLGT for
portions of West Virginia, Maryland, and southwest PA, which
includes Somerset County. Farther east, 3-hr flash flood
guidance in southern PA is 4"+, which would indicate that
flooding is rather unlikely there. The MRGL in effect for the
rest of our area covers the potential for locally heavy
downpours and isolated ponding on roadways in the strongest
showers and storms.

Model consensus shows QPF max shifting to the east Thursday
morning as the frontal system moves across PA. The remainder of
Thursday should feature scattered showers/PM t-storm as upper
low and cooler temps aloft begin to impinge on the area. Most of
this activity will be diurnally driven with little to no precip
expected Thursday night. Post frontal westerly/downslope flow
along with breaks of sun in the dry slot should push temps back
up on Thursday with highs peaking in the mid 80s in the Lower
Susq Valley.

By Friday, the upper low parks overhead and will stick around
into the weekend. Cold temperatures aloft will support
sufficient instability for diurnally driven showers and storms
that are scattered in nature. Dewpoints in the low 50s and
temperatures in the mid 60s to near 80 will feel great after a
very brief glimpse of summer.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Reloading of the mean Glakes/NE U.S. upper trough by a few
shortwave troughs dropping Southeast will maintain the chc for
mainly diurnal showers/isolated to sctd TSRA.

Current indications are that by the end of the weekend into
early next week, the upper tough becomes positively tilted and
the low may retrograde slightly and stall over the Great Lakes
region, especially considering the additional energy helping to
deepen the trough. This will continue the unsettled pattern of
diurnally driven showers and thunderstorms through at least
Monday afternoon. Long range ensembles currently show the trough
lifting after Tuesday morning with lower pops for showers/TSRA
as we head into the middle of next week.

Temperatures are likely to average somewhat below climatology
for early to mid-June, with daily highs in the upper 60s and
70s, and overnight lows in the 50s to lower 60s.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
Still just some high and mid level clouds over the area as of
130 AM. An isolated shower and then pops up on the radar across
the far south.

Guidance still shows lower CIGS working northwestward in a few
hours, so held onto timing in the TAFS.

Earlier discussion below.

Widespread VFR conditions and light winds are expected the rest
of the evening. However, a moistening southeast flow off of the
Atlantic Ocean will result in developing stratus late tonight
across Central PA. Latest ensemble prob charts indicate the low
cigs will develop between 06Z-11Z with the highest probability
of IFR/LIFR (~70pct) over the Lower Susq Valley (MDT/LNS) and a
lower probability (~50pct) further north and west.

Diurnal heating/mixing is likely to result in rising cigs during
the daylight hours of Wednesday, with mainly MVFR to low IFR
cigs by afternoon based on model soundings.

A warm front lifting out of the Ohio Valley will spread showers
and thunderstorms into the area during the afternoon and
evening, potentially resulting in a brief dip to IFR vsby in a
few spots.

The arrival of the warm front Wed evening may result in
improving cigs Wed evening over Southern PA, where predominantly
VFR conditions are likely. However, latest guidance indicates an
upsloping southerly flow ahead of the warm front will likely
result in cigs falling back to IFR over the N Mtns.

Outlook...

Thu...AM showers/low cigs possible, mainly N Mtns. Isolated PM
tsra impacts possible Southeast PA.

Fri...Slight chance of a brief PM shower/vis reduction, mainly
NW Mtns.

Sat...AM low cigs possible NW Mtns. Slight chance of PM
shower/vis reduction NW Mtns.

Sun...Slight chance of a brief PM shower/vis reduction, mainly
NW Mtns.

&&

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

&&

$$

SYNOPSIS...Lambert/Banghoff
NEAR TERM...Lambert/Banghoff
SHORT TERM...Lambert/Steinbugl/Banghoff
LONG TERM...Lambert/Fitzgerald/Bowen
AVIATION...Fitzgerald/Martin