Area Forecast Discussion
Issued by NWS Greer, SC

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735
FXUS62 KGSP 070742
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
242 AM EST Wed Dec 7 2016

.SYNOPSIS...
A drying trend will continue for several days as high pressure
eases into the area. A reinforcing cold front will arrive tonight
and early Thursday, bringing the coldest airmass so far this
season into the area. High and low temperatures well below normal
will persist Thursday night through Saturday before a moderating
trend commences early next week when the next cold front arrives.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 230 AM EST Wednesday: Low pressure that brought us all the
rain yesterday continues to push east with strong WSW flow aloft
over us. Plentiful low level moisture remains in place across the
area and with light winds at the surface this has created a perfect
environment for fog and low clouds, with visibilities 1/4 mile or
less for many sites across the Piedmont. Went ahead and issued a
Dense Fog Advisory for all the NC/SC/GA Piedmont, even though
technically not ALL the areas meet criteria, it`s close enough and
the fog continues to expand. Fog should burn off quickly later this
morning with temperatures rebounding to seasonal normals.

Meanwhile, the next weather-maker in the form of a strong upper low
will be sliding east across the U.S./Canada border, with a very
strong and very cold Arctic high diving into the High Plains late
today. The front ahead of the high isn`t really all that wet and
with each run they`ve trended drier. WPC doesn`t even bring any QPF
into the forecast area anymore, but for the sake of consistency did
blend in a little from the previous run (what`s 0.01" among
friends?). What little moisture there is associated with the front
will all get squeezed out over the mountains (though the rest of us
could see an increase in clouds overnight tonight). It`ll be cold
enough that the higher elevations will likely see some snow showers
or at least flurries, but again just not enough moisture for any
accumulations.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 200 AM EST Wednesday...A broad upper trough will drift east
across the Ohio Valley to the Mid-Atlantic coast Thursday thru
Friday. This trough will bring a strong, but rather dry, cold front
thru the region on Thursday. Strong 850 mb CAA will ramp up across
the NC mountains during the day, resulting in gusty winds and
falling temps. The piedmont will see temps near normal, while the
mountains will be about 10 degrees below normal Thursday. The gusty
winds will linger thru the overnight in the high terrain, but become
fairly light in the piedmont. Temps will fall into the teens in the
mountains and 20s piedmont. The combination of wind and temps will
result in wind chills in the 0 to -10 F range toward daybreak
Friday. Wind chill advisory is -5, and generally only elevations
above 5000 ft look to get that cold.

On Friday...a modified arctic air mass will build in from the NW.
Winds will gradually subside in the mountains, but it will still
feel brisk, with temps at least 10-15 degrees below normal, despite
sunny skies. The center of the high settles over the central
Appalachians by 12z Saturday. Lighter winds will keep wind chills
above advisory criteria, but overall, it will be a chilly night.
Lows in the teens to mid 20s.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 130 AM EST Wednesday:  The very cold airmass in place Saturday
under surface high pressure centered over our region will move east
and offshore from the mid Atlantic on Sunday. This will bring a
change in wind to a more southerly direction resulting in a
significant warming trend to around normal to start the week.  The
upper pattern will be nearly zonal from this weekend to mid
week across our nation with an average slight trough east of the
Rockies. The next shortwave will cross the Plains Sunday with some
increased in moisture coming out of the Gulf across the SE. Expect
some upslope showers ahead of this system to occur late Sunday and
Sunday night from near Clayton GA to Tryon NC. The southerly 925mb
wind of 15 to 30kts will shift to SW early Monday ending the upslope
affect as it will be more parallel to the ridge lines. Both the GFS
and ECMWF thins out or slightly dries out the approaching frontal
precip band Sunday night into Monday. The GFS dries it out a bit
more. Either way there will be scattered showers over the whole area
but more initially over the NC mountains. There may be some very
brief upslope precip along the TN and NC border north of AVL late
Monday but that is mostly shown on the EC which may be the lower
confidence model. The newest GFS dries our area out rapidly late
Monday with no upslope in Mtns. High pressure builds in briefly on
Tuesday then a mostly dry cold front is nearing from the NW late
Tuesday night. Increase in clouds as a result.

Temperatures of 10 to 15 degrees below normal Saturday will modify
to near normal for Max Temps Monday and Tuesday.

&&

.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Incredible uncertainty especially at the
beginning of the period with cigs and vsbys. Guidance is all over
the place. Downslope winds remain in place but beginning to subside.
Strong up-valley flow continues at KAVL as well. Plenty of low level
moisture remains across the area to support fog/low clouds and
certainly looking at satellite trends it looks like widespread low
cloudiness continues to expand and blossom east of the escarpment.
Have improved trends somewhat for KAVL but for all others kept IFR
to LIFR in overnight. Drier air will push into the area later today
which should scour out any low clouds but then another wave of
moisture associated with a strong but mainly dry front will lead to
increasing clouds again toward the end of the period, and thus some
MVFR has been introduced. Except at KAVL, winds generally lgt/vrb
through the period with some variation in predominant direction
depending on location of surface features.

Outlook: Another front will approach late tonight and early Thursday
with some light precip/restrictions possible. Dry and much colder
through the weekend.

Confidence Table...

            07-13Z        13-19Z        19-01Z        01-06Z
KCLT       High  84%     High  97%     High 100%     High 100%
KGSP       Med   61%     High  90%     Med   77%     High  88%
KAVL       Med   63%     High  98%     High  91%     High  86%
KHKY       Low   35%     High  96%     High 100%     High  81%
KGMU       Low   49%     High  93%     Med   78%     Med   79%
KAND       Med   63%     High  80%     High  84%     High  85%

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...Dense Fog Advisory until 10 AM EST this morning for GAZ018-026-
     028-029.
NC...Dense Fog Advisory until 10 AM EST this morning for NCZ035>037-
     056-057-068>072-082-502-504-506-508-510.
SC...Dense Fog Advisory until 10 AM EST this morning for SCZ004>014-
     019.

&&

$$
SYNOPSIS...DEO
NEAR TERM...TDP
SHORT TERM...ARK
LONG TERM...DEO
AVIATION...TDP



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