Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 200651
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
251 AM EDT Fri Oct 20 2017

.SYNOPSIS...
High pressure will remain over the eastern CONUS through the
upcoming weekend. Low pressure is likely to track west of the
state early next week with a trailing cold front coming through
Pennsylvania Tuesday or early Wednesday.

&&

.NEAR TERM /UNTIL 8 AM THIS MORNING/...
Extensive but thin high clouds are masking sct-bkn low clouds
over the NW. However, the low clouds are breaking up a bit.
Still, enough clouds and a little wind and slow temp and
dewpoint falls so far are enough to nudge min temps up a deg or
two - mainly in the NW and on the hill tops of the S.
Otherwise, no precip with the dry front. Fog not likely, but a
patch here or there is possible.

&&

.SHORT TERM /8 AM THIS MORNING THROUGH 6 PM SATURDAY/...
Strong upper ridge expands northward from the Ohio Valley on
Friday...with large scale subsidence leading to another sunny
day across central PA. 925mb temps of around 14C should
translate to max temps in the upper 60s and low 70s.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Both the 12Z ECENS and NAEFS maintain an anomalous upper level
ridge over the area through the weekend. This should ensure
fair weather with above average temperatures Saturday to Sunday.
Ensemble mean 925/850 temps support highs of 70-75F, while
light wind and dry air result in seasonably cool nights.

All medium range guidance indicating there will be a digging
northern stream trough early next week over the upper midwest
and Miss Valley that will eventually phase with closed low
lifting out of the southern states. Considerable model
difference exist with respect to timing/track of this southern
stream shortwave, resulting in arrival of showers as early as
Monday or as late as Tues PM. For now, have slowly ramped up the
chance of rain beginning late Monday. However, will reserve the
best chance of rain for Tuesday/Tues night, when bulk of med
range guidance track shortwave and attendant plume of Gulf of
Mexico moisture across the area. Early QPF estimates from
operational runs and GEFS indicate 1+ inch amounts are possible.

A period of near to below normal temperatures appears likely for
the second half of next week, as upper trough swings east into
the area. However, both GFS and ECMWF ensemble systems indicate
the thrust of the chilly air will be directed west of Pa and
there are indications of rising heights/milder weather across
the entire eastern conus toward the end of the month.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
Current GOES-16 and fcst simulated IR satellite data shows
a stream of sct-bkn high clouds drifting south from the eastern
Great Lakes over central PA airspace this morning. The high
clouds should obscure patchy valley fog formation which will
make for poor detection on satellite. With high clouds overhead
and guidance not showing fog/visibility restrictions will
simply maintain continuity from previous TAFs with TEMPO
5SM/SCT002 at KIPT. Overall, VFR remains the prevailing flight
category.

Outlook...

Sat-Sun...Patchy AM valley fog otherwise VFR.

Mon-Tue...VFR to MVFR/IFR. Showers likely. LLWS. Strong FROPA.

Wed...Breezy. Sct showers. MVFR NW 1/2.

&&

.CLIMATE...
Month-to-date, October 2017 is the warmest October on record at
Harrisburg and Williamsport.

&&

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

&&

$$
SYNOPSIS...Dangelo/DeVoir
NEAR TERM...Dangelo
SHORT TERM...DeVoir
LONG TERM...Fitzgerald/Ceru
AVIATION...Steinbugl
CLIMATE...



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