884
FXUS61 KCTP 251916
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
316 PM EDT Tue Jun 25 2024

.SYNOPSIS...
High pressure will drift off of the Mid Atlantic Coast tonight,
allowing increasing moisture to return to the region.

Heat will build again by Wednesday leading to a chance of
thunderstorms by late in the day and Wednesday night as a cold
front pushes through the state.

Dry weather with comfortable humidity on Thursday and Friday
will be followed by another cold front late Saturday or early
Sunday of next weekend.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Extensive mid and high clouds venting from decaying MCS over the
eastern GLAKS and OH Valley have been streaming overhead for
most of the day. This appears to have shaved 2 to 4 degrees
Fahrenheit off of temperature trends, but thinning high clouds
may allow mid to late afternoon temps to catch up to overall
boundary layer warming and reach within a few degrees of
previously forecast highs. We did cut maxes by 3-4 degrees
throughout, but the slight increase in dewpoints accompanying
slightly higher temps than yesterday (and less of that
refreshing breeze) will counteract the underperforming temps.

Focus is on moisture and heat return scenario tonight and
Wednesday, and resulting complicated convective mode/forecast
tonight and Wednesday. We start out with near term CAMs
differing wildly on their initialization of the aforementioned
ongoing MCS over OH, and how much recovery will be needed in
these areas late tonight and Wednesday morning to support
potentially another MCS in the Wednesday morning hours that can
impact convective evolution Wednesday afternoon and evening.

At the very least, a warm front will try to lift northeastward
across the Eastern Grt Lks tonight with a few showers and
possibly a tsra possible over the west/northwest mountains.
Much less certain is the potential for showers or thunder
farther east across the Central Ridge and Valley region of the
state as the instability axis over Lake Erie, sags to the SE.
Again, MCS propagation early Wednesday morning turning "right"
towards the WV/MD panhandles can greater influence POPs farther
north, and confidence is low on the timing and track of the
Wednesday morning MCS. PW surges to between 1.0 and 1.5" by late
tonight, at least providing the fuel for potential activity
overnight and Wednesday morning.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY NIGHT/...
The aforementioned surging PWs and falling heights ahead of an
upstream cold front will overall bring a much better chance of
widespread showers and scattered strong to potentially severe
thunderstorms Wednesday afternoon/evening. How we get there is
far less certain, owing to the aforementioned uncertainty in
MCS formation and track. There is a scenario where the early
morning MCS pinches off moisture and instability to areas
farther north as it curves southward, stably stratifying much of
central PA early in the day and challenging temp/instability
recovery ahead of the advancing cold front. Those details will
need to play out to give us a better idea of convective setup
later Wednesday and Wednesday evening, but the SPC slight risk
for southeast and south central PA certainly highlight areas
with the greatest threat for strong storms to develop later
Wednesday.

A ribbon of relatively strong low to mid level (west to
southwest) winds of 50 to 55 kts, combined with moderate
instability, suggests organized convection and locally severe
weather is possible Wed PM. Latest ensemble plumes indicates
most likely aerial average rainfall Wed will be between one half
and one inch.

High temps Wed should reach the upper 70s to low 80s across the
Northern Mtns and upper 80s to low 90s respectively across the
Central and SE zones.

After the return of warmer and humid conditions Wednesday, Thu
and Fri turn comfortable once again with dewpoints dropping
back into the 50s (and 40s up north).

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
Predictability begins to wane by this weekend regarding the
timing/amplitude of the shortwave trough expected to move from
the Great Lakes region into the Northeast/New England. There is
some potential for stronger deep-layer flow to overspread an
increasingly moist warm sector, but details regarding the
surface pattern remain uncertain, and rather warm temperatures
aloft could limit destabilization potential. Some potential for
strong to locally severe storms could evolve on Saturday ahead
of a cold front from the Ohio Valley into parts of the
Northeast. WPC has also suggested the potential for a marginal
to slight risk of locally heavy/excessive rainfall on Saturday
with pwats surging to +2SD above normal. The timing of the
main synoptic cold front on Sunday is also uncertain with some
potential for a secondary strong/svr tstm risk.

Confidence is significantly higher concerning the arrival of
another refreshing Canadian high pressure system directing a
comfortable (less humid) airmass into CPA for early next
week...a seasonably cool and dry start to July!

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
High confidence in VFR flying through the evening into the first
half of tonight/06Z Wed. Uncertainty ramps up overnight into
early Wednesday morning with potential for showers and t-storms
moving into the airspace from the north/west. Can`t rule out
some cig restrictions in the 06-15Z window based on the latest
probabilistic guidance, but the overall pattern/low level flow
don`t provide a strong enough signal to maintain in TAFs outside
of KBFD. Confidence continues to trend lower from late Wed
morning through 18Z and beyond given highly conditional/potential
strong to severe t-storm scenario. A 40kt low level jet from
230-260 degrees will maintain LLWS at KBFD between 00-06Z.

Outlook...

Wed...Thunderstorm impacts likely.

Thu-Fri...Generally VFR.

Sat-Sun...Thunderstorm impacts possible.

&&

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

&&

$$

SYNOPSIS...Lambert/DeVoir
NEAR TERM...Lambert/DeVoir/Dangelo
SHORT TERM...Lambert/DeVoir
LONG TERM...Banghoff/Steinbugl
AVIATION...Steinbugl/Bauco