Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 190347
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1147 PM EDT Fri Aug 18 2017

.SYNOPSIS...
A cold front will pass east of the area tonight. An upper
trough will move across the region Saturday afternoon and
evening. Temperatures will stay above normal but rise even
higher each day through Tuesday as a ridge builds aloft. Another
cold front should trigger showers around mid-week and the week
should end on a cooler note.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Satellite loop at 01Z still showing a line of cumulus along
trailing cold front running from near KIPT south to near KHGR.
Will maintain the chance of a shower/storm along and east of
this boundary through the late evening hours. Latest radar
trends and HRRR support POPs of only around 20 pct across this
area through around midnight, then patchy fog will become the
issue. Latest SREF and downscaled NAM suggest the weakest
gradient and best chance of fog will be across the Susq Valley,
but patchy valley fog is also likely further west.

A push of drier air behind the cold front, along with light wind
and mostly clear skies, should allow temps to fall to near 60F
over the northwest counties and to the upper 60s in the
southeast part of the forecast area.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
After a mostly sunny Saturday morning, a sharp upper trough
will swing eastward from the Ohio Valley, generating afternoon
showers and tstorms. Will maintain the highest POPs across the
northwest counties, where passage of trough will coincide with
time of max heating during early to mid afternoon. SPC continues
to highlight the northwest half of the forecast area in a MRGL
risk. Model data showing decent mid level winds and deep layer
shear, but limiting factor will be only modest instability.
Expect convection to diminish in intensity/coverage as it pushes
into eastern Pa during the cooling hours of Saturday evening.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
The mid range models are all in good agreement on the timing and
strength of the passing shortwave Saturday night. Once that
passes, the heights will rise and become quasi-zonal. This will
bring fair weather to the region Sunday through Tuesday. Dry
westerly flow will also bring warm summertime temperatures with
Tuesday continually trending warmer. A new shortwave moving
through SRN Canada will an bring an increasing chance for rain,
possibly as early as Tuesday afternoon over western sections of
the forecast area.

There are differences in timing of the rain with the ECMWF
suggesting it holds off until Tuesday night. Blended MOS POPs
show a small chance of showers moving into western sections
Tuesday afternoon, but the highest POPs are reserved for the
overnight.

Cyclonic flow aloft will then dominate the flow pattern through
Thursday. The cool air aloft will help trigger a few mainly
diurnal showers Wednesday and Thursday. The showers will tend to
favor northern and western higher elevations. Temperatures will
be significantly cooler for the second half of the week.

&&

.AVIATION /04Z SATURDAY THROUGH WEDNESDAY/...
Mainly clear skies over the region this evening. Fog is
expected for most of the area tonight, with MVFR to IFR
restrictions. Lowest restrictions expected in the southeast,
where most significant rain fell this evening.

An upper level trough and rather strong forcing passing
directly overhead in the cooler air aloft could make scattered
SHRA/TSRA across the northern third/half of Pennsylvania on
Saturday afternoon.

Much drier air will make for a mainly-VFR Sun-Mon with only
valley fog in the AM a potential issue.

.OUTLOOK...

Sat...Mainly VFR, but with sct SHRA/TSRA northern 1/3.
Sun-Mon...Mainly VFR, but restrictions in morning fog.
Tue-Wed...SHRA/TSRA poss.

&&

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

&&

$$
SYNOPSIS...Dangelo/Fitzgerald
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald
LONG TERM...La Corte/Ceru
AVIATION...Jung


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