930
FXUS61 KCTP 050754
AFDCTP

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

.SYNOPSIS...
*Mostly cloudy and not as warm but more humid today into
 tonight with locally heavy downpours and a few gusty
 thunderstorms possible
*Trending slightly warmer and less humid Thursday with risk of
 soaking showers and storms shifting into eastern PA
*Cooler/more comfortable conditions Fri-Sun with a couple of
 passing showers or a t-storm mainly during the afternoons

&&

.NEAR TERM /THROUGH TONIGHT/...
IR satellite loop shows low stratus developing across portions
of the mid and lower Susquehanna Valley beneath layered altocu
and cirrus decks. Increasingly moist southeast flow should allow
for low clouds/patchy fog to expand over parts south central
and southeastern PA through daybreak. Best chance for a couple
of predawn rain showers will likely exist within a north-south
oriented axis of high pwats btwn 1-1.5" extending northward from
the DC area through Franklin/Adams/York County toward KSEG.

Latest suite of hi-resolution model and ensemble guidance
progresses a blossoming area of showers and t-storms (generally
from SW to NE) across the CWA from late morning through the
afternoon and evening. This initial bout of convection during
peak diurnal heating appears to be tied to shortwave feature
embedded in SWly mid-level flow tracking to the northeast from
eastern KY through WV and into south central PA 18-24Z.

Cloud cover will limit instability to some extent with mean
MLCAPE values running in the 500-750 J/kg range, but that should
be sufficient to drive potential for locally heavy to perhaps
excessive rainfall amounts given the available moisture
anomalies. The persistent south/southeast low level flow
will surge pwat values to 1.5-2.0" or +2-3SD. WPC has added a
SLGT risk ERO (level 2/4) to cover much of the southern tier
zones with the Laurel Highlands into the adjacent southern
Alleghenies being the most vulnerable based on lowest FFG. FFGs
are much higher as you go farther east in southern PA peaking
around 4" in 3hr across most of the lower Susq Valley -- which
suggests a less favorable or lower probability setup. The 05/00Z
3hr QPF neighborhood probs of >3" peak around 10% over the
Laurels and far southern Alleghenies btwn 18-21Z before
shifting over the South Mountain area in the 21-24Z timeframe.
We will add mention of excessive rain to the HWO based on the
trends in the WPC ERO and PWAT anomalies, but will hold off on
issuing a FF watch at this time.

Switching gears from heavy rain to severe storm risk, the focus
areas for strong storms should be in the SPC MRGL risk areas:
1) Northwest Alleghenies (Warren, Elk, McKean) in very
moist/unstable airmass downstream of a cold front pushing
through the OH Valley and 2) just south of the MD line where a
small but favorably curved low-level hodograph will be present.
The 05/00Z HREF progs bulk shear values below 30kts over the
majority of PA -- so we are not overly impressed with potential
for severe wx and would lean toward heavy rain/FF being a larger
(albeit marginal) risk or concern.

The aforementioned cold front should continue to produce showers
and perhaps a few storms it moves into the area tonight with the
bulk of 24hr QPF occurring in the 18Z Wed to 06Z Thu window.

Not as warm today as cloud cover will trim about 10F from
yesterday`s (near record) max temps with highs going from
80-90F to 70-80F, but it will feel rather sticky and quite humid
with dewpoints in the 65-70F range. Muggy conditions expected
tonight with showers, patchy fog and fcst min temps btwn 60-70F
or +10-15F above early June climo.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
Model consensus shows QPF max shifting east of the Susq River
Thursday as the frontal system slows its eastward progression
as it exits the Keystone State. Max POPs are shaded along the
eastern periphery of the CWA with scattered showers/PM t-storm
lagging farther to the west 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 /SATURDAY 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...Steinbugl
NEAR TERM...Steinbugl
SHORT TERM...Steinbugl
LONG TERM...Lambert/Fitzgerald/Bowen
AVIATION...Fitzgerald/Martin