Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 200751
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
351 AM EDT Sun Aug 20 2017

.SYNOPSIS...

High pressure with fair weather will build across the area
through Monday. A strong cold front will sweep southeast across
the area Tuesday night. Cooler and drier conditions will return
for the second half of the new week.

&&

.NEAR TERM /THROUGH TONIGHT/...

Night time satellite images show the valleys overflowing with
fog and low clouds as light winds and high pressure build in
behind yesterday`s secondary cold front.

After the low clouds and fog burn off, high pressure will
provide the region with fair weather today. Model soundings
indicate just a few cumulus developing during the afternoon. 850
temps near 14C should translate to max temps from the upper 70s
across the Allegheny Plateau, to the mid 80s across portions of
the Susq Valley.

A comfortable night for sleeping is in store tonight as high
pressure moves over the state. Some patchy valley fog will be
possible once again late at night.

&&

.SHORT TERM /MONDAY/...

Dewpoints will begin to creep back up as high pressure slips
officer and a low level southerly flow develops. A weak lee-
side surface trough is depicted over central and eastern PA in
the short term deterministic guidance, and scattered convection
is made to develop with afternoon heating about this feature
over SERN areas. The SREF and GEFS both show some respectable
CAPE developing in the increasingly humid airmass so a stronger
storm cannot be ruled out.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...

The big weather maker looks to be a potent late summer cold
front that latest timing shows passing through the region
Tuesday night and early Wednesday.

After a surge of heat Monday and Tuesday, with some southern
locations possibly nudging 90 each day, the strong front will
bring a refreshingly cool and dry airmass to the region for the
second half of the week.

The biggest question will be severe potential with the front.
Latest timing shows the front just moving through central Ohio
by Tuesday evening. The SREF and GEFS develop very little CAPE
near the cold front and into central PA, keeping a finger of
unstable air confined mainly to the coastal plain well out ahead
of the front. So it remains to be seen if parameters can line
up for widespread severe storms with the actual front as at
this point it doesn`t seem like the best set up despite the
magnitude of the airmass difference and strength of the wind
fields. Once again the models are hinting that the coastal plain
may be where the action is as the best CAPE and shear are
aligned there associated with the lee-side troughing.

The remainder of the week into the weekend looks to be cool and
mainly dry as a sprawling high moves slowly eastward out of
southern Canada. Interesting to note that the deterministic
models show 850 temps as cold as 3C just north of the Canadian
border behind the cold front, a reminder the change in seasons
is not all that far away.

&&

.AVIATION /07Z SUNDAY THROUGH THURSDAY/...
Some lower clouds at AOO, but expect these to be gone soon.

Minor adjustments to the 06Z TAFS.

Earlier discussion below.

Skies now clear, with VFR conditions across all of Central
Pennsylvania in the wake of the line of thunderstorms.

Expecting fog development in most areas overnight. MVFR to
locally IFR conditions are likely.

After morning fog dissipates, VFR conditions should prevail
across the region for Sunday.

Another VFR day for Monday, except again for some morning fog.

.OUTLOOK...

Sun-Mon...Mainly VFR, but restrictions in morning fog.
Tue...Thunderstorm impacts likely into the overnight.
Wed...Morning SHRA...then becoming VFR
Thu...VFR.

&&

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

&&

$$
SYNOPSIS...La Corte
NEAR TERM...La Corte
SHORT TERM...La Corte
LONG TERM...La Corte
AVIATION...Jung/Martin



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