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-- Discussion containing changed information from previous version are highlighted. --
802
FXUS61 KCTP 190554
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
154 AM EDT Thu Oct 19 2017

.SYNOPSIS...
For the most part our weather will be dominated by a surface
high and an upper-level ridge through late Sunday. A weak
short-wave comes over the ridge on Thursday without significant
moisture. Our first real chance of rain will be early next week
when a trough moves our way. By mid-week we could see some below
normal temperatures with a deep trough just to our west.

&&

.NEAR TERM /UNTIL 7 AM THIS MORNING/...
Another cool and tranquil night is underway with high pressure
over the area resulting in efficient radiational cooling. Based
on 05Z dewpoint depressions, as well as NAM/SREF output, patchy
valley fog appears a good bet early this morning across the
eastern half of the state. Temps on track to bottom out from the
upper 30s in the coolest valleys, to the mid 40s on the hilltops
and urban areas of the Lower Susq Valley.

&&

.SHORT TERM /7 AM THIS MORNING THROUGH FRIDAY NIGHT/...
Warm air, with maximum temperatures 5 to 10 degrees above
normal, will continue through Friday. A shortwave tracking well
north of Pa will push a dying cold front into our region late
today. Models indicate just enough moisture preceding this front
to produce sct late day cu across the northwest mountains.
Otherwise, it will be another sunny day. Expect a bit more wind
today with the weak frontal surge. Rain chances through Friday are
near zero.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
A strong upper level ridge of high pressure will support above
average temperatures through the weekend. This will further add
to the anomalous October warmth which should help to secure a
spot in the top-10 warmest Octobers - if not top 5 or even #1.
Both GFS and ECMWF ensemble systems continue to indicate a
pattern flip by the middle of next week with a period of colder
(near/below normal) temperatures starting around October 25th.
The depth and longevity of the emerging upper trough and
subsequent cooler pattern remains in question - so we will have
to wait and see how much of a dent it can put in the strongly
positive month-to-date departures from climatology.

On the precipitation side, the prolonged dry spell ends early
next week as a cold front moves across the Appalachians. Stream
separation differences/closed low development in some of the
deterministic models leads to increasing spread and thus
uncertainty in the forecast details such as timing. The GOM will
be open for moisture inflow northward ahead of the front. So
will keep continuity and favor max POPs in the Monday night-
early Tuesday timeframe.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
GOES-16 fog channel is starting to show valley fog formation
across portions of the central and eastern airspace. Surface obs
indicate eastern TAF sites have decoupled with temp/dewpt
spreads tightening to within a few degrees. Therefore expect
greatest odds for restrictions at KIPT, KLNS and KMDT in that
order. Fog should dissipate by 14z giving way to VFR. To the
west in ZOB sector, expect VFR to prevail through the period.
Wind gusts will reach the 15-20kt range over the western 1/2 of
the airspace from late this morning through the afternoon. A dry
cold front will push across the airspace this evening and
early tonight accompanied by a light wind shift from 220-250 to
270-330 degrees. High pressure moves back over PA late tonight
into Friday morning.

Outlook...

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

Mon...VFR to MVFR. Showers possible into Monday night. LLWS
likely Monday night into early Tuesday.
-- End Changed Discussion --

&&

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

&&

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

&&

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