Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 191202

Area Forecast Discussion
National Weather Service State College PA
802 AM EDT Tue Sep 19 2017

A ridge of high pressure at the surface and aloft will stay
locked in place over Pennsylvania for the next 7 days. This
dominant weather feature will provide fair, warm and generally
dry weather throughout this entire period.


Another comfortable night/early morning with light wind as
Central PA remains in the sweet spot of weather - between
Hurricane Jose (spinning about 250 NM east of KORF) and a
stalled out frontal boundary extending from the Lower Great
Lakes to the Midwest States.

The main weather maker this morning will come in the form of
patchy dense fog across portions of north-central and
northwestern PA where significant pockets of clear skies exist.
Elsewhere, a slightly anomalous llvl easterly flow will push
plenty of stratus clouds westward across the forecast area and
act to minimize the thickness of any fog that does form.

Min temps around sunrise today will be in the upper 50s to
lower 60s...which will average around 10 deg above normal.

Morning stratus and areas of generally light fog will be
burning off to a partly-mostly sunny afternoon as the upper
ridge axis continues to reside right over central PA.

The western extent of the outer bands of showers associated
with Hurricane Jose (that will be a few to several hundred miles
east of the Delaware coast during the late morning and afternoon
hours) will brush our SE zones where we`ll continue to play it
safe and mention slight chc or chc pops with very low QPF (if
any) of under one-tenth of an inch.

With expected light rain and thicker cloud cover, temps will
likely be suppressed a bit across that region of the CWA
compared to recent days (but will still be 4-5 deg F above
normal). Max temps elsewhere will continue to run a solid
6-10F above normal for mid September.


LLVL flow will become light and northerly tonight as slowly
weakening Tropical Storm Jose drifts to near the latitude of
southern PA (40 deg N) by 12Z Wed.

Expect much less in the way of stratus tonight and just some
wisps of cirrus on the edge of Jose`s circulation, so it
appears that locally dense valley fog will come into play once
again after 06Z Wednesday. Min temps early Wednesday will be
at least 2-4F lower than early Tuesday.

A spectacular Wednesday is on tap with abundant sunshine, and
just a few flat cu and thin cirrus to paint the otherwise azure
blue sky.

Max temps Wednesday will once again range from the mid to upper
70s across the higher terrain of the north and west, to the L80s
in the SE.


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 Friday-Sunday,
which will translate to well above normal temps. Enjoy!

High temps over this several day period will be 10-15F above
normal with little or no chance of rain through at least Monday.

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.


Satellite and observations depict widespread MVFR to IFR
restrictions this morning in low stratus and fog. The main
forecast challenge will be timing of improvement which should
occur in the 14-17z timeframe. Model data, climatology and
persistence support a high confidence of widespread VFR
conditions from the afternoon into the evening. Persistence
would favor another period of sub-VFR restrictions in fog/low
clouds later tonight into Wednesday morning.


Wed-Sat...Patchy valley fog possible each morning.


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




NEAR TERM...Lambert
SHORT TERM...Lambert
LONG TERM...Lambert/Gartner
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