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000
FXUS61 KCTP 161310
AFDCTP
Area Forecast Discussion
National Weather Service State College PA
810 AM EST Sat Dec 16 2017
.SYNOPSIS...
Cold northwest flow and lake effect snow showers in the lee of
Lake Erie are expected today. High pressure and a brief
moderating trend in the temperature are expected by Sunday. A
series of cold fronts will move across the area late Sunday into
Wednesday. Windy and colder temperatures will follow.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Upper trof moving off of the eastern seaboard this morning with
channeled northwest flow organizing lake effect snow bands over
the eastern lakes and depositing over my northwest mountains.
CAMs indicate incoming banding will extend into the central and
north central mountains this morning with light coatings
expected there. Going advisories in good shape with several
more inches of accumulation expected through this afternoon.
Lake effect snow showers will diminish by late this afternoon as
heights continue to rise and inversion heights lower. It will
still be colder than normal with highs ranging from the upper
20s northwest to around 40 over the south.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
HIgh pressure centered over eastern Ontario and southern Quebec
and over the southeastern coastal states tonight will bring
fair and cold conditions. Upper ridging will be tempered on
Sunday by an embedded disturbance in the return moisture flow
west of the sfc ridge axis, which may bring scattered rain and
snow showers to the southern third of central PA Sunday
afternoon. Amounts will be barely measurable, and with marginal
sfc temperatures am not expecting any accumulations...just
melting at this time. Highs will range from the mid 30s north to
the lower 40s south on Sunday.
&&
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
This coming week will see the long-wave upper level trough that
has been dominating out weather shift east as a deep trough digs
over the Western U.S. Lake enhanced snow showers should be
ending by Saturday night with the surface high pressure ridge
moving off the coast and the winds becoming move west to
southwesterly.
The western trough kicks a strong shortwave out across the
Plains Sunday into Monday. The associated low center will move
northeast across the Great Lakes staying to our North and west.
This system will bring in warmer air in southwest flow ahead of
it. However, we may be cold air dammed near the surface so the
+1 to -2C air at 850 hPa may not translate to a warm boundary
layer. The warm advection should bring snow and snow to rain in
the south but QPF amounts are light. Will have to watch for
potential for some ice also Sunday night.
We look to move into a fast moving pattern of weak shortwaves
and chances for precipitation (mainly over the northern
mountains) through the week. As a northern stream wave zips by
to our north by Monday night, it should drag cold air back into
the region Tuesday into Wednesday. The northwest flow triggers
snow in relatively high POPS in NW PA due to LES. This cold
surge should be relatively fleeting and high pressure and a
potential surge of relatively warmer air follows Thursday.
The warm advection and approaching cold front will likely
produce increased potential for snow in NW Thursday into Friday.
Farther south any precipitation would likely be mixed or rain.
A strong frontal boundary will likely push another surge of
cold air into the region Friday into Saturday as the eastern
long wave trough tries to re-establish itself.
&&
.AVIATION /13Z SATURDAY THROUGH WEDNESDAY/...
The snow bands continue to weaken though bands will continue
through the NW and central mountains. Most of the snow is
producing VFR to MVFR restrictions, however periods of heavier
bands will bring IFR vsbys to BFD and JST Arctic fropa
overnight will shift winds to the northwest, producing a more
favorable over- lake trajectory. This will invigorate snow
showers over the western and northern mountains.
Result will be highly variable visibility conditions in the
north and west as snow showers drift in and out.
Outlook...
Sat...Scattered snow showers and local restrictions NW/Laurels.
Sun-Mon...Mainly VFR.
Tue-Wed...mainly VFR, but possible restrictions in the western
and northern mountains in snow showers.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 4 PM EST this afternoon for
PAZ004-005.
&&
$$
SYNOPSIS...DeVoir
NEAR TERM...DeVoir
SHORT TERM...DeVoir
LONG TERM...Watson
AVIATION...Jung/Ceru


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