-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 201133
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
733 AM EDT Wed Sep 20 2017

.SYNOPSIS...
A ridge of high pressure at the surface and aloft will extend
across Pennsylvania through next Tuesday. This dominant weather
feature will provide fair, warm and generally dry weather
for this entire period.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Earlier clear skies and strong radiational cooling with light
wind and moderately high sfc dewpoints in the 50s to lower 60s
has set us up for another foggy morning throughout most of the
central and northern valleys of the commonwealth. Temp/dwpt
spread is now basically zero across most locations to the NW of
the Interstate 81 corridor with temps in the l-m 50s across the
mtns, and upper 50s to low 60s throughout the Central Mtns and
Middle Susq Valley.

Look for areas of dense fog to become fairly widespread for a
few hours either side of daybreak today.

The western influence of moisture from what is now tropical
storm Jose (that`s parked about 250 miles south southeast of
Islip Long Island) was seen in the form of bkn-ovc strato cu
pushing slowly wwd across the Lower Susq Valley and Western
Poconos. Fog early today will be minimized in those places due
to the extent of cloud cover and still mild temps with a 5-8 deg
F temp/dwpt spread.

Min temps will be about 2-4F lower than early Tuesday over the
northern half and similar to Tuesday across the the southern
half - and notably milder than normal, especially in the cloud
covered SE.

After the fog burns off in the valleys late this morning, a
spectacular Wednesday late morning and afternoon is on tap with
abundant sunshine and just a few flat cu and thin cirrus to
paint the otherwise azure blue sky.

There could be a couple of showers off to our SW in a very weak
and eroding trough, but only result for us will be potentially
an increase in cloud cover over the Laurel Highlands.

Mid afternoon Max temps will once again range from the upper
70s across the higher terrain of the north and west, to the
lower 80s (and maybe a few mid 80s) in the southeast thanks to a
milder start with the early morning cloud cover.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
The broken record continues for tonight and Thursday under the
persistent ridge along the spine of the Appalachians. mainly
clear skies, light wind and a slight bump up in sfc dewpoint
will provide optimal conditions for another night of locally
dense and fairly widespread valley fog.

Low temps early Thursday should be 2-4 deg F milder than early
Wednesday, and similar increases in high temps from the prior
day are also expected with highs near 80F across the nrn and wrn
mtns, and low to mid 80s elsewhere.

Sky cover (after the dissipation of the morning fog) will be
generally scattered with some flat afternoon cu and areas of
thin cirrus.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
The overall pattern hasn`t changed much, there is a good
overall consensus in the models for the end of the work week.
For much of this period, a 590 dam closed 500 hPa high will
drift slowly out of the midwest states, and become centered over
western PA by late this weekend through early next week.

The GEFS forecasts showed this feature as a closed 5880 m ridge
over us with near +2 sigma above normal heights which will
translate to well above normal temperatures. High temps from
Friday through the weekend will be 10-15F above normal with
little or no chance of rain until Monday at the very earliest.

Lows early each morning will be consistently in the mid and
upper 50s across the northern and western mtns, to lower 60s in
the larger SE metro areas.

Min temps may cool off slightly for this weekend thanks to deep
dry air and a light N to NW llvl flow of drier dewpoint air at
the sfc.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
GOES-16 fog channel imagery shows widespread valley fog
confined mainly to the west of the Susquehanna River. The outer
edge of cloud shield associated with TS Jose is drifting over
the southeast airfields and has precluded fog formation. Locally
dense fog will produce local cig/vis AOB airfield minimums.
Expect fog to dissipate through mid morning with VFR conditions
this afternoon and evening. Persistence fcst favors more fog
restrictions late tonight into Thursday morning.

.Outlook...

Thu-Sun...Patchy valley fog possible each morning. Otherwise
VFR with generally light winds and minimal clouds.
-- End Changed Discussion --

&&

.CLIMATE...
Astronomical Fall/Autumnal Equinox begins at 4:02 PM Friday
September 22, 2017.

&&

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

&&

$$
SYNOPSIS...Lambert/RXR
NEAR TERM...DeVoir/Lambert
SHORT TERM...Lambert/RXR
LONG TERM...Ceru/Gartner
AVIATION...Steinbugl
CLIMATE...