High Wind Watch 1, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
417 AM EST Tue Jan 8 2019

.SYNOPSIS...
A weak cold front crosses the area from the west tonight. Cold high
pressure will build in behind the front and linger until a moist low
pressure system reaches the forecast area early in the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 345 AM EST: Latest IR satellite imagery showed mid to high
level clouds draped across the region with a back edge along the
mountains. Low clouds continue below and behind the clouds as the
the main cold front remains well to the west of the region. Radar
continues to show shower activity approaching the region from the
west, however ground based observations aren't picking up much. Have
confined low end PoPs to the mountains for today, mainly western
upslope regions as a result of the lack of precip response. Cloud
cover should gradually decrease through the day east of the
mountains, especially NC Piedmont. With the warm air mass in place
most areas will make it back into the 60s for highs today. Breezy
southwest winds are expected this afternoon and evening especially
across the higher terrain. A sharp cold front is expected to push
through the region this evening with strong cold air advection
continuing through the night. This will support gusty northwest
winds focused across the mountains and NC foothills where a wind
advisory will be posted for late tonight through Wednesday night. A
high elevation Wind Watch will also be issued shortly for northern
mountains above 3500 feet as wind gusts in excess of 58 mph is
possible. In addition to the wind, there is a slight chance of
northwest flow rain showers turning to snow later this evening
across the northern NC mountains near the TN border. Available
moisture is limited through tonight, so currently expect only light
accumulations at most. Post frontal cold air advection and mostly
clear skies will support low temps for tonight in the 30s to near
40, except 20s higher elevations. However, the windy conditions in
the mountains and NC foothills will make it feel about 10 degrees
cooler.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 145 AM EST Tuesday: Upper trough axis moves east of the area
Wednesday with NW flow remaining over the area through the end of
the period. A channeled short wave drops through the trough and over
or just north of the area Wednesday then to our east Wednesday
night. The upper jet follows a similar pattern with decent upper
divergence. The NAM/SREF are farther south with these features than
the rest of the guidance, although even those have them nearby. The
moisture is deep enough, the CAA strong enough, and the NW upslope
flow good enough for snow showers to develop in the usual NW flow
areas late Wednesday into Wednesday night. There is some concern for
convective snow squalls developing given the forcing and weak
elevated instability seen on the NAM forecast soundings. The GFS is
weaker given the more northward alignment of features and even
weaker elevated instability. Have increased snow shower chances
across the northern mountains given these trends, but even using the
higher NAM QPF, snow amounts top out around an inch in the usual
higher elevation locations. The larger concern will be the strong
winds developing across the mountains. A strong pressure gradient
and mountain wave action develops. This combines with the increasing
low level winds for gusts to potentially reach warning gusts across
the higher elevations of the northern NC mountains and advisory
level across the rest of the NC mountains and foothills. Wind chill
values will approach advisory levels across the higher elevations
Wednesday night as well. Gusty conditions develop outside of the
mountains but well below advisory level. Highs Wednesday will be
around 5 degrees below normal across the mountains and near normal
elsewhere.

The pressure gradient relaxes Thursday and Thursday night as high
pressure slowly builds into the area. Winds will diminish quickly as
a result. Snow showers will end quickly Thursday morning as well.
Heights will rise slightly as a ridge approaches from the west. The
cold air mass will be fully over the area, so highs will be 5 to 10
degrees below normal with lows up to 5 degrees below normal.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 415 AM EST Tuesday: Ridging Friday is short lived as northern
and southern stream waves phase to our west on Saturday and cross
the area Sunday and move east on Monday. The guidance differs on the
strength timing and location of the phasing. The guidance agrees
that high pressure sets up in cold air damming position on Friday
and holds on through Saturday as a Miller A/B hybrid low develops
and moves by on Saturday then east on Sunday. There is some
disagreement on the timing and actual track the low takes. They also
agree on precip moving into the mountains Friday night and spreading
across the area Saturday and Saturday night. The GFS moves the low
east of the area Sunday with some lingering NW flow precip across
the mountains which dissipates Sunday night. The ECMWF is slower
with the movement of the low and shows a secondary upper wave
crossing the area keeping precip in place Sunday and Sunday night
then dissipating Monday. Have opted for a model blend which has the
highest PoP Saturday and Saturday night with chance PoP Sunday then
diminishing Sunday night.

With the guidance trending toward more of a hybrid low, this
suggests much more of a mixed bag of precip with a warm nose
developing Saturday and spreading north across the area changing
precip to rain for all but the areas along and near the Blue Ridge
escarpment where deeper cold air can linger in the CAD. Have used
the top down method with a blend of the GFS and ECMWF thermal
profiles to create the weather grids. This shows a mixed bag at
onset Friday night changing to snow across most of the are along and
north of I-85 by morning. Then the mixed bag returns as the warm
nose moves in Saturday. Wintry mix is limited to the Blue Ridge area
east along the I-40 corridor Saturday night with all areas turning
to rain on Sunday. NW flow snow develops Sunday night. Highest storm
total snow is along and near the Blue Ridge from the NC/GA/SC border
north across NC. This lines up well with the winter storm
probabilities from WPC. Amounts drop off west and east of there with
little to no amounts along and south of I-85. Of course, this is
highly subject to change as the event approaches.

&&

.AVIATION /09Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: Increasing low level moisture associated
with a weak warm front will support continued lowering cigs
overnight with IFR cigs likely for KCLT and possible for KHKY with a
20 percent chance fo LIFR through 15Z. SW Wind gusts of 15-20 kts
possible after between 15Z and 00Z. Gusty west to northwest winds
focused across the mountains expected behind a moisture starved cold
front passing through the region between 00Z and 06Z with mainly VFR
conds.

Outlook: Gusty northwest winds expected to continue through
Wednesday or Wednesday night, focused across the mountains. Expect
VFR cigs except KAVL where MVFR/IFR cigs are possible at times.

Confidence Table...

            09-15Z        15-21Z        21-03Z        03-06Z
KCLT       High  81%     High 100%     High  98%     High 100%
KGSP       High 100%     High  98%     High  89%     High 100%
KAVL       High 100%     High 100%     High 100%     High 100%
KHKY       High  94%     High 100%     High 100%     High 100%
KGMU       High 100%     High  98%     High  89%     High 100%
KAND       High 100%     High  98%     High  89%     High 100%

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...Wind Advisory from 11 PM this evening to 7 AM EST Thursday for
     NCZ033-035-048>053-058-059-062>065-501>510.
     High Wind Watch from this evening through Thursday morning for
     NCZ033-049-050.
SC...None.

&&

SYNOPSIS...RWH
NEAR TERM...Munroe
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...Munroe

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
455 AM EST Mon Jan 7 2019

NCZ033-048>053-058-059-062>065-501-503-505-507-509-081000-
Avery-Madison-Yancey-Mitchell-Swain-Haywood-Buncombe-Graham-
Northern Jackson-Macon-Southern Jackson-Transylvania-Henderson-
Caldwell Mountains-Burke Mountains-McDowell Mountains-
Rutherford Mountains-Polk Mountains-
455 AM EST Mon Jan 7 2019

This Hazardous Weather Outlook is for western North Carolina.

.DAY ONE...Today and tonight.

Hazardous weather is not expected at this time.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

Very gusty northwest winds with gusts up to 55 mph, mainly across
the higher elevations, will be possible behind a departing cold front
Tuesday night into Wednesday. In addition, cold temperatures combined
with the winds could lead to wind chill values as low as 10 below
zero, mainly across the higher elevations. Light snow showers will
also be possible across the higher elevations along and near the
Tennessee border.

A low pressure system will bring precipitation to the area Friday
night through Sunday. Temperatures may be cold enough for the
precipitation to fall as snow or a wintry mix. However, there is
quite a bit of uncertainty with this system regarding timing,
location of wintry precipitation, and precipitation amounts.

.SPOTTER INFORMATION STATEMENT...

None.

GAZ010-017-018-026-028-029-NCZ035>037-056-057-068>072-082-502-504-
506-508-510-SCZ001>014-019-081000-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Alexander-Iredell-
Davie-Catawba-Rowan-Cleveland-Lincoln-Gaston-Mecklenburg-Cabarrus-
Union-Greater Caldwell-Greater Burke-Eastern McDowell-
Greater Rutherford-Eastern Polk-Oconee Mountains-Pickens Mountains-
Greenville Mountains-Greater Oconee-Greater Pickens-
Greater Greenville-Spartanburg-Cherokee-York-Anderson-Abbeville-
Laurens-Chester-Greenwood-
455 AM EST Mon Jan 7 2019

This Hazardous Weather Outlook is for northeast Georgia, piedmont
North Carolina, western North Carolina and upstate South Carolina.

.DAY ONE...Today and tonight.

Hazardous weather is not expected at this time.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

A low pressure system will bring precipitation to the area Friday
night through Sunday. Temperatures may be cold enough for the
precipitation to fall as snow or a wintry mix. However, there is
quite a bit of uncertainty with this system regarding timing,
location of wintry precipitation, and precipitation amounts.

.SPOTTER INFORMATION STATEMENT...

None.