Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 112010
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
310 PM EST Mon Dec 11 2017

.SYNOPSIS...
High pressure will weaken before a strong cold front crosses the
area overnight. Dry high pressure will build back in Wednesday with
temperatures dropping below normal. A slow warming trend begins late
in the week.

&&

.NEAR TERM /THROUGH TUESDAY NIGHT/...
As of 250 PM EDT Monday: A Winter Weather Advisory and Wind
Advisory have been issued with this forecast package for before
daybreak on Tuesday, along with a Wind Chill Advisory beginning
overnight Tuesday into Wednesday morning, all for portions of
the NC mountains.

Abundant sunshine along with a return to nearly zonal flow aloft has
allowed for temperatures to gradually climb into the upper 40`s to
mid to upper 50`s this afternoon. As conditions remain quiet,
temperatures will dip into the mid 30`s overnight, with the upper
20`s/low 30`s across the northern foothills into the NC mountains.
Expect clouds to increase tonight ahead of the next approaching
system, a shortwave/clipper system, well defined by latest water
vapor imagery. As this system continues to progress eastward across
the Ohio Valley this afternoon and through tonight, it`s associated
dry cold front will push west to east, making it`s way through the
mountains late overnight into the early morning hours on Tuesday.

Behind the front, low-level moisture along the TN/NC border and a
return to northwest flow will bring snow showers to the NC mountains
on Tuesday. New snow accumulations of 1 to 2 inches are possible
right along the TN/NC border, as noted in the Winter Weather
Advisory. Increased CAA will also bring increased northwest winds
across the entire area, with sustained winds 10 to 15 kts and higher
gusts to near 20 kts across the Upstate and Piedmont. Into the
mountains, higher winds are expected thus warranting a wind advisory
for portions of the NC mountain counties, some for areas above 3500
ft. Aside from the mountains, conditions will remain quiet
weather wise on Tuesday, as lingering clouds begin to decrease into
the evening hours. Expect high temperatures in the upper 40`s to
lower 50`s across the area on Tuesday, with the exception of 30`s
across the mountains.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
As of 245 PM EDT Monday: The short term fcst period kicks off on
Tuesday night amidst broad troffing across the eastern CONUS aiding
prominent northwest flow into the southern Appalachians.  With that,
llv moisture sufficient for snow showers will remain in place along
the spine of the Appalachians at fcst initialization.  Thus the near
term winter weather advisories as well as wind advisories will carry
over until Wednesday morning given gusty winds and snow totals in
the 2-3" range.  In addition, these potent winds combined with the
caa regime will lead to wind chills below zero across much of the
high terrain, yet reaching advisory criteria across the northern
mountains, as well as locales above 3500ft southward.  Therefore a
wind chill advisory for Tuesday night has also been issued that will
run through 7AM Wednesday for wind chills less than minus 5 degrees.

Beyond that, the forecast dries out yet remains cold with
temperatures below normal levels through Wednesday.  Meanwhile
another weak clipper system sliding through/into the OH valley will
pass north of the fcst area Wednesday night into Thursday likely
with little fanfare across northeast GA and the western Carolinas.
Lastly, the pattern looks to shift on Thursday as upper/mid lvl flow
backs swly thanks to the ejection of the persistent longwave trof.
This pattern shift will lead to some gradual warming yielding
temperatures that will approach normal by the end of the period.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 225 PM EST Monday: the extended fcst picks up at 00z on
Friday with another round of impressive upper-lvl energy diving
southward on the on the backside of the persistent eastern CONUS
upper trof. The trof axis is expected to pass over the fcst area
by late Fri/early Sat and then rapidly lift NE of the region over
the next 12 to 24 hrs. The pattern then flattens out as we move into
Sunday. From this point onward, the extended models diverge a fair
amount wrt the synoptic pattern. The ECMWF deepens another upper
trof to our west and brings it to our area by late Sun/early Mon
while the latest 12z GFS and Canadian are about 12 to 24 hrs slower
with the trof. At the sfc, the pattern will remain dynamic thru
the period with a fair amount of uncertainty wrt the pattern
evolution. We do expect a coastal low to spin up on Friday just
off the NC Coast and become a strong Nor`easter over the next 24
hrs or so. Dry high pressure will slide in behind the low for
Sat and then move offshore by early Sun. Another low will spin up
to our west on Sun and bring another cold front to our doorstep
by late Sun/early Mon.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
At KCLT and Elsewhere: Potential for short-lived marginal MVFR cigs
and -SNSH at KAVL Tuesday morning. Other expect VFR through the
valid TAF period with increasing winds on Tuesday.

Expect nearly clear skies with light southwest winds at the
terminals (northwest at KAVL) through early this afternoon ahead of
the next approaching system. High clouds will increase later today
and into tonight along with increasing winds (AOB 10 kts) as a
system moves through the Great Lakes/Ohio Valley today and it`s
associated cold front pushes through Tuesday morning. Northwest flow
will follow the front, allowing for a slight increase in moisture
across the NC mountains. This influx of moisture could bring
marginal MVFR cigs to KAVL, along with wintry precipitation.
However, confidence is low attm regarding snow potential at KAVL,
thus have not introduced into going TAf attm. Otherwise, VFR will
continue on Tuesday with increasing NWS winds AOB 15 to 20 kts with
gusts to near 25 kts possible.

Outlook: Potential for restrictions at KAVL Thursday night into
Friday with a a NW flow snow event. Otherwise expect VFR.

Confidence Table...

            15-21Z        21-03Z        03-09Z        09-12Z
KCLT       High  81%     High  82%     Med   68%     Low   56%
KGSP       Med   70%     Med   75%     High  83%     Med   64%
KAVL       High  94%     High  85%     Med   70%     High  87%
KHKY       High 100%     High  83%     Med   66%     High 100%
KGMU       Med   76%     High  86%     High  85%     Med   63%
KAND       Med   76%     Med   65%     High  90%     Med   61%

The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:

www.weather.gov/gsp/aviation

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...Winter Weather Advisory from 4 AM Tuesday to 7 AM EST
     Wednesday for NCZ033-048>052.
     Wind Advisory from 4 AM Tuesday to 7 AM EST Wednesday for
     NCZ033-048>052-058-059-062>064.
     Wind Chill Advisory from 10 PM Tuesday to 7 AM EST Wednesday
     for NCZ033-048>052-059.
SC...None.

&&

$$

SYNOPSIS...SBK
NEAR TERM...SGL
SHORT TERM...CDG
LONG TERM...JPT
AVIATION...SGL



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