Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
248 PM EDT Sun Sep 9 2018

.SYNOPSIS...
The back door cold front currently across the area will retreat
northward as a warm front on Monday as a cold front approaches from
the west.  The cold front will move into the area on Tuesday and
stall through mid-week as Hurricane Florence approaches the East
Coast.  Hurricane Florence may make landfall in the Carolinas by
Friday morning, but the extent of impacts to the western Carolinas
and northeast Georgia remains uncertain.

&&

.NEAR TERM /THROUGH MONDAY/...
Showers and a thunderstorm or two are gradually expanding in
coverage this afternoon, mainly across the mountains and foothills
along/south of the I-85 corridor, where sbCAPE has increased to
2000-2500 J/kg. The primary focus for convection this afternoon,
other than the usual terrain effects, will be the former back door
surface front that has stalled near the NC/SC border. Outflow
boundaries produced by clustering convection over north and central
Georgia will probably eventually provide yet another initiation
mechanism across the western Upstate and northeast GA. Likely pops
still appear warranted across roughly the middle half of the
forecast area, not to mention the mountains. The main hazard
potential with this activity will be localized flash flooding
produced by training cells, although a pulse storm producing brief
downbursts cannot be ruled out, especially with cell mergers.

As New England/Nova Scotia surface high begins oozing into the
Atlantic tonight, and S/SW low level flow increases, the boundary
will become increasingly diffuse, and may begin drifting to the
north. It should nevertheless provide a continued focus for at least
scattered showers and a few storms well into the overnight hours,
with a continued threat of locally excessive rainfall. Mechanical
lift will also improve into the high terrain of northeast GA and
southwest NC, resulting in scattered showers becoming increasingly
focused in those areas toward daybreak. Min temps will remain around
5 degrees above climo.

Occluding/weakening frontal zone and associated moisture band will
push into the NC mountains from East TN on Monday, but is unlikely
to make significant headway into the forecast area. Meanwhile,
moderate instability should again develop over the entire forecast
area, with pre-frontal/lee side trough providing a focus for
convective initiation east of the mtns. 70-80 pops will be
advertised in association with the moisture band across the NC mtns,
with generally 40-60 pops favored elsewhere. Max temps will again be
above normal in most locations, but certainly not as warm as was
seen during the first week of the month.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 230 PM Sunday: The middle part of the week will see a
transition between the broadly confluent southerly flow on Tuesday
courtesy of broad upper troffing to our west and the large upper
anticyclone off the east coast, to a more easterly flow as that
upper anticyclone extends westward over the Mid-Atlantic and
Carolinas on Wednesday. It will be the westward extension of the
ridge that aims Florence toward the east coast of the U.S. as we
head toward the end of the week (more on that in a bit). With these
developments, it seems likely that a weakening sfc boundary will
not make it over the mountains, leaving us with a conditionally
unstable air mass for Tuesday and Wednesday, and more late summer
warmth and humidity. Mainly diurnal showers and thunderstorms will
be the rule both days, with maybe a bit more coverage late Wednesday
as the more easterly flow takes hold. Not much change from earlier
thinking as to the severe weather possibilities. Again, sbCAPE
will be sufficient but mid-level lapse rates are relatively poor,
so a few will not be ruled out. Temps will run above normal thru
the period.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 245 PM Sunday: The extended period begins with Hurricane
Florence approaching the Carolina coastline.  As we have been saying
for many cycles now, Florence's forecast track will continue to
evolve in the days ahead and specific impacts for the western
Carolinas and northeast Georgia will too evolve in response to
the anticipated track.  Remember, the Day 5 Track Forecast Cone of
Uncertainty from the National Hurricane Center (NHC) is over
450 miles wide and the Day 4 cone is nearly 350 miles wide. This
uncertainty and potential error must be considered when making
plans. However, as it stands right now with the latest local
forecast, which is based off of the NHC's and Weather Prediction
Center's coordinated forecasted location of Florence through
Day 7, the most significant impacts across our area will be
focused to the north and east along the NC Piedmont, northern
NC mountains and foothills, the I-77 Corridor, and the Charlotte
metro. These impacts include the potential for tropical-storm
force winds (>39 mph) beginning during the day on Thursday and
heavy rainfall potential from Thursday morning through Sunday
from any rainbands that develop on the western side of the storm
as Florence slowly tracks north. These impacts would shift west
with any westward shift in Florence's forecast track, so all
residents of the western Carolinas and northeast Georgia need to
continue to stay weather aware and prepared through mid-week.  Nevertheless, there has been some consistency to this forecast
for a few periods now and it results in the rest of the area
being underneath the subsident extremities of the hurricane
(sinking and stable airmass) heading through the end of the
period on Monday morning. If the center of circulation remains
to our east, the entire area would experience northeasterly flow
on Thursday backing to northerly Thursday evening into Friday
morning and northwesterly later Friday and persisting
northwesterly through early Monday morning. This would result in
upslope showers from the west for the mountains and a downslope
(i.e., sinking, drying) component to the winds for the Upstate
and northeast Georgia, which would reduce precip chances there
heading through the weekend. This would have the effect of
reducing dewpoints to the mid 60s heading into Sunday, but
overall, the flow would promote continued warmth under partly
sunny skies and both low and high temperatures would remain
well-above normal. Regardless of what our weather ends up being,
current guidance continues to suggest very slow storm motion
with Florence meaning we will still be dealing with the
potentially significant effects of the system into early next
week.
For the latest track forecast and wind speed arrival times, please
visit the National Hurricane Center's website at:
https://www.nhc.noaa.gov.

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
At KCLT and elsewhere: Low MVFR cigs are expected to lift to the
higher end of MVFR at KHKY by late afternoon before returning to IFR
by late evening or so. Otherwise, restrictions through this evening
should be limited to convection occurrence. Showers are gradually
expanding in coverage across the area this afternoon, warranting
VCSH or VCTS at all sites beginning during the next 0-2 hours. For
now, tempos are limited to KCLT and KHKY from late afternoon through
early evening, but I suspect most of the other terminals will
require at least a tempo at some point, but timing is uncertain. The
convective potential is expected to continue well into the evening,
and perhaps the early part of the overnight, especially at the NC
sites (with KHKY being particularly susceptible). Otherwise, all
sites are expected to see cigs lower from mid/late evening through
the overnight, with LIFR conditions likely at KHKY and IFR or low
MVFR conditions likely at the other sites. The flight category
should be relatively slow to improve on Monday, but most sites
should be at least MVFR by the end of the forecast period.

Outlook: An active period of mainly diurnal showers and
thunderstorms is expected to continue through the middle part of the
week before diminishing a bit during late week. Overnight/early
morning restrictions in fog and/or stratus are also expected,
primarily in the mountain valleys.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High  87%     High  89%     Med   62%     Med   65%
KGSP       High 100%     High 100%     Med   78%     Med   79%
KAVL       High  99%     Med   78%     Med   67%     Med   77%
KHKY       High  81%     Med   76%     High  81%     High  80%
KGMU       High 100%     High 100%     Med   78%     Low   54%
KAND       High 100%     High 100%     High  97%     Med   67%

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...None.
SC...None.

&&

SYNOPSIS...JMP
NEAR TERM...JDL
SHORT TERM...PM
LONG TERM...JMP
AVIATION...JDL

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
332 AM EDT Sun Sep 9 2018

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-101000-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Avery-Alexander-
Iredell-Davie-Madison-Yancey-Mitchell-Swain-Haywood-Buncombe-Catawba-
Rowan-Graham-Northern Jackson-Macon-Southern Jackson-Transylvania-
Henderson-Cleveland-Lincoln-Gaston-Mecklenburg-Cabarrus-Union-
Caldwell Mountains-Greater Caldwell-Burke Mountains-Greater Burke-
McDowell Mountains-Eastern McDowell-Rutherford Mountains-
Greater Rutherford-Polk Mountains-Eastern Polk-Oconee Mountains-
Pickens Mountains-Greenville Mountains-Greater Oconee-
Greater Pickens-Greater Greenville-Spartanburg-Cherokee-York-
Anderson-Abbeville-Laurens-Chester-Greenwood-
332 AM EDT Sun Sep 9 2018

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

.DAY ONE...Today and tonight.

Numerous showers and thunderstorms will develop across the western
Carolinas and northeast Georgia today through tonight. Thunderstorm
intensity will peak this afternoon and evening. Cloud-to-ground
lightning, gusty winds, and locally heavy rainfall will be possible.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

The track of Tropical Cyclone Florence will need to be closely
monitored by interests across the western Carolinas and northeast
Georgia throughout the week. Some impact from this system in our
area will be possible late in the week, perhaps from late Thursday
through Saturday, but uncertainty remains too high to be specific
about the exact impacts or precise timing. Please continue to follow
the latest forecasts from the National Hurricane Center.

.SPOTTER INFORMATION STATEMENT...

None.

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
248 PM EDT SUN SEP 9 2018

NCZ070-071-091915-
Gaston NC-Mecklenburg NC-
248 PM EDT SUN SEP 9 2018

...A STRONG THUNDERSTORM WILL IMPACT SOUTHWESTERN MECKLENBURG AND
SOUTHEASTERN GASTON COUNTIES UNTIL 315 PM EDT...

At 248 PM EDT, Doppler radar was tracking a strong thunderstorm 9
miles east of Gastonia, or near Belmont, moving northeast at 5 mph.

Locations to be impacted include...
Central Charlotte, Southwest Charlotte, Mt Holly, Belmont, Cramerton,
Mcadenville, Charlotte Douglas Airport, Paw Creek, Southpark Mall and
Freedom Park.

Wind gusts up to 45 mph and pea size hail will be possible in these
areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Gusty winds can blow down trees that are dead, or that have weakened
root systems. Outdoor furniture and similar items can be tossed
around if not anchored. Seek shelter indoors.

&&

LAT...LON 3514 8105 3515 8105 3515 8108 3524 8112
      3539 8097 3512 8081
TIME...MOT...LOC 1848Z 241DEG 6KT 3521 8102

SGL

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
302 PM EDT SUN SEP 9 2018

NCZ068-508-SCZ007-008-091930-
Greater Rutherford NC-Cleveland NC-Cherokee SC-Spartanburg SC-
302 PM EDT SUN SEP 9 2018

...A STRONG THUNDERSTORM WILL IMPACT SOUTHEASTERN RUTHERFORD...
SOUTHWESTERN CLEVELAND...NORTH CENTRAL SPARTANBURG AND NORTHWESTERN
CHEROKEE COUNTIES UNTIL 330 PM EDT...

At 302 PM EDT, Doppler radar was tracking a strong thunderstorm 8
miles south of Forest City, or 5 miles north of Chesnee, moving
northeast at 10 mph.

Locations to be impacted include...
Forest City, Chesnee, Bostic, Cliffside, Henrietta, Harris and
Caroleen.

Wind gusts up to 40 mph and pea size hail will be possible in these
areas.

LAT...LON 3513 8189 3519 8195 3536 8183 3517 8165
TIME...MOT...LOC 1902Z 222DEG 8KT 3522 8183

SGL

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
313 PM EDT SUN SEP 9 2018

NCZ071-091945-
Mecklenburg NC-
313 PM EDT SUN SEP 9 2018

...A STRONG THUNDERSTORM WILL IMPACT WEST CENTRAL MECKLENBURG COUNTY
UNTIL 345 PM EDT...

At 312 PM EDT, Doppler radar was tracking a strong thunderstorm 6
miles west of Uptown Charlotte, or near Charlotte Douglas Airport,
moving northeast at 10 mph.

Locations to be impacted include...
Uptown Charlotte, Central Charlotte, Northwest Charlotte, Freedom
Park, The Plaza, Charlotte Douglas Airport, Paw Creek, East
Charlotte, Southwest Charlotte and Northeast Charlotte.

Wind gusts up to 50 mph and nickel size hail will be possible in
these areas.

LAT...LON 3516 8099 3517 8100 3518 8100 3520 8101
      3521 8100 3522 8101 3527 8101 3538 8090
      3518 8074
TIME...MOT...LOC 1912Z 231DEG 8KT 3524 8095

SGL

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
343 PM EDT SUN SEP 9 2018

NCZ071-092030-
Mecklenburg NC-
343 PM EDT SUN SEP 9 2018

...A STRONG THUNDERSTORM WILL IMPACT CENTRAL MECKLENBURG COUNTY UNTIL
430 PM EDT...

At 343 PM EDT, Doppler radar was tracking a strong thunderstorm 4
miles north of Uptown Charlotte, or near Northeast Charlotte, moving
northeast at 10 mph.

Locations to be impacted include...
Uptown Charlotte, Huntersville, Central Charlotte, Northeast
Charlotte, Northwest Charlotte, Freedom Park, Reedy Creek Park, The
Plaza, Paw Creek and Hidden Valley.

Wind gusts up to 45 mph and dime size hail will be possible in these
areas.

LAT...LON 3517 8087 3529 8097 3545 8086 3529 8067
      3528 8067
TIME...MOT...LOC 1943Z 219DEG 7KT 3530 8083

SGL

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
404 PM EDT SUN SEP 9 2018

GAZ010-017-018-026-092045-
Franklin GA-Rabun GA-Stephens GA-Habersham GA-
404 PM EDT SUN SEP 9 2018

...A CLUSTER OF THUNDERSTORMS WILL IMPACT NORTHERN FRANKLIN...
STEPHENS...HABERSHAM AND SOUTHWESTERN RABUN COUNTIES UNTIL 445 PM
EDT...

At 403 PM EDT, Doppler radar indicated the leading edge of a cluster
of thunderstorms along a line extending from 6 miles west of
Clarkesville to 6 miles northwest of Carnesville, and moving
northeast at 15 mph.

Locations to be impacted include...
Toccoa, Clarkesville, Cornelia, Baldwin, Gumlog, Demorest, Mount
Airy, Alto, Martin and Avalon.

Wind gusts up to 40 mph and dime size hail will be possible in these
areas.

LAT...LON 3482 8365 3488 8366 3491 8363 3469 8334
      3468 8334 3448 8306 3433 8339 3443 8338
      3446 8340 3449 8354 3446 8358 3451 8366
      3454 8362 3460 8365 3462 8364 3465 8366
      3468 8364 3474 8362 3477 8363 3480 8368
TIME...MOT...LOC 2003Z 210DEG 14KT 3463 8363 3441 8333

SGL

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
421 PM EDT SUN SEP 9 2018

NCZ071-072-092045-
Mecklenburg NC-Cabarrus NC-
421 PM EDT SUN SEP 9 2018

...A STRONG THUNDERSTORM WILL IMPACT CABARRUS AND CENTRAL MECKLENBURG
COUNTIES UNTIL 445 PM EDT...

At 421 PM EDT, Doppler radar was tracking a strong thunderstorm 6
miles southwest of Downtown Concord, or over Charlotte Motor
Speedway, moving northeast at 15 mph.

Locations to be impacted include...
Downtown Concord, Kannapolis, Northeast Charlotte, West Concord,
Harrisburg, Mt Pleasant, Reedy Creek Park, Charlotte Motor Speedway,
Coddle Creek Reservoir and UNC-Charlotte.

Wind gusts up to 40 mph and pea size hail will be possible in these
areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Gusty winds can blow down trees that are dead, or that have weakened
root systems. Outdoor furniture and similar items can be tossed
around if not anchored. Seek shelter indoors.

&&

LAT...LON 3536 8039 3519 8068 3534 8086 3551 8073
      3551 8069 3539 8037
TIME...MOT...LOC 2021Z 236DEG 12KT 3535 8069

SGL