Area Forecast Discussion


268 
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