Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 202158

Area Forecast Discussion
National Weather Service State College PA
558 PM EDT Sun Aug 20 2017

High pressure will bring clear skies and seasonal temperatures
to the region tonight. Look for partly cloudy skies with a
chance of afternoon thunderstorms on Monday. A strong cold front
will approach the region later on Tuesday, bringing a chance of
stronger thunderstorms with it. Cooler and drier conditions
will return for the second half of the week.


High pressure overhead with strong subsidence leading to clear
skies overnight. low temperatures fairly close to seasonal
norms. Look for patchy valley fog close to sunrise.


High pressure moves east with southerly and more warm and humid
flow returning. Model show a weak shortwave drifting across the
area during the afternoon and this combined with heating will
trigger a few thunderstorms. Have increased pops to account for
this. Any convection will decrease quickly after sunset with a
warm and muggy night as area in the warm sector ahead of cold


The big weather maker this week still looks to be a potent late
summer cold front that will pass through the region Tuesday
evening into early Wednesday.

After a surge of heat and humidity Monday and Tuesday, with
some southern locations possibly nudging 90 each day, the strong
front will bring a noticeably cooler and drier airmass to the
region starting midweek and lasting through the weekend and into
next week.

The biggest question will be how much severe potential will
accompany the front. Latest timing shows the front just moving
through central Ohio by Tuesday evening. The SREF and GEFS
develop very limited 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. But wind fields
increase heading into Tue eve, and this may be enough combined
with the difference in the two airmasses to kick storms off and
keep them propagating eastward. For now, Slight Risk from SPC
encompasses much of the CWA with Marginal Risk in the SE.

The remainder of the week into the weekend turns cooler 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. Chilliest readings look to be the
mornings of Fri/Sat/Sun with high centered overhead, dipping
lows into the 40s over the Northern Mountains (and deeper
valleys of the Central Mountains) and solidly into the 50s


High pressure over the region will ensure VFR conditions and
very light wind for the balance of the evening. Some patchy valley
fog is expected across northern Pa early Monday morning, but
the odds of significant reductions at any central Pa airfields
are low. Perhaps a 10 percent chance of a brief dip to IFR at
KIPT around dawn.

Scattered afternoon thunderstorms will form Monday afternoon, as
high pressure passes east of the region. Despite predominantly
VFR conditions, a brief reduction is possible from an afternoon
or evening thunderstorm. The best chance will be across the
eastern airfields, including KIPT,KMDT and KLNS.


Tue...Thunderstorm impacts likely into the overnight.
Wed...Morning SHRA...then becoming VFR




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