Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
235 PM EDT Sun Aug 1 2021

.SYNOPSIS...
A front will remain nearly stationary from the Gulf coast states to
the North Carolina coast through most of the week. Waves of low
pressure will ride along the front giving our area scattered to at
times numerous showers and a few thunderstorms.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 220 PM: Surface front has reached the northern border of
our CWA and extends westward thru TN, just ahead of well-defined
shortwave trough axis seen on WV imagery. 1000-2000 J/kg SBCAPE is
analyzed ahead of the front, and in turn a band of showers/storms
has now pushed south of the I-40 corridor. We will only get more
unstable with time so this activity should be maintained as it
propagates thru the rest of the Piedmont. Downsloping appears to
keep the activity from growing to some degree in the lee of the
mountains. However, new cells should fire along the front as it
passes the more rugged terrain, per CAM depictions showing increase
in activity once the front reaches the SC border. Largely downslope
W-NW winds aloft would however seem to have somewhat of a limiting
effect on our convection (some stable wave clouds are seen above
the cumulus, indicating some capping). Revised PoPs reflect CAM
consensus as far as location, although radar mosaic so far today
suggests their sparse depiction of activity is underdone to some
degree. PoPs remain generally in scattered range. Progged PWATs
from GFS/NAM/ECMWF are all near 2 inches this afternoon across
the southern half of the CWA; SBCAPE does tick up a bit higher
than typical, 2500 J/kg or more in the lower Piedmont. Deep-layer
shear remains supportive of multicells/clusters, and heavy rain
still looks like the main threat. The DCAPE present ahead of the
front will diminish as moisture pooling occurs, but not out of the
question a storm will tap into the dry air and produce localized
wind damage.

Still anticipating the front to push south of the CWA by this
evening; instability diminishes a little faster than usual with
midlevel subsidence/warming, so convection should quickly fizzle
after the fropa. Main signal from guidance is for mountain valley
fog. Assuming we manage to clear out across the Piedmont T/Td trends
from most models suggest at least patchy fog could develop there,
but drier air will also be working in behind the front. Thus it may
be a race between the drying and the radiational cooling; often the
latter wins out. However, not yet confident enough to say exactly
where in the Piedmont is most at risk of fog. Lows will be mostly
in the 60s, save for some upper 50s in the higher mtn elevations.

Subsident thermodynamic profiles are expected to linger through
Monday, so overall convective chances look below climo. Furthermore,
lower dewpoints and temps (both several degrees below normal) will
have an impact. We will remain under the eastern CONUS trough,
with a second shortwave digging over the lower MS Valley Monday,
pretty much as soon as heights would be set to rebound following
the first one. This does reintroduce some midlevel moisture from the
frontal zone, so various sources depict a small PoP in our far south
in addition to the small convective response near the Blue Ridge.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 215 PM EDT Sunday: Models are in good agreement on
consolidating shortwave energy digging into the longwave trough over
the OH/TN valleys, bringing strong deep-layer Q-vector convergence
atop the forecast area late Monday night thru Tuesday. This
mid-level energy should induce a sfc wave along a stalled frontal
boundary invof central GA Monday night. Low-level flow will back out
of the east and bring Atlantic moisture into the western Carolinas
overnight. The GFS seems to be producing some in-situ CAD, as precip
falls in slightly dry BL air and locks in some cooler air. The
NAM doesn't look as stable, with Bufkit soundings showing sbCAPE
Tuesday aftn. As long as there is widespread precip around Tuesday,
I think we will stay wedged. Temps will struggle to get into the
upper 70s to lower 80s, which is about 10 deg below normal. Forcing
will be strong, but the heavy rain and any severe threat looks to
stay near the coast on the warm side of the stationary front.

A second shortwave will reinforce the mean longwave trough
Wednesday, keeping the pattern in place. Another sfc wave will
likely develop to our south/southwest, but the models are not in as
good agreement and it will be weaker than the Tuesday system. So
the models show whatever CAD we might have should break. I'm not
so sure, and will feature plenty of cloud cover and below normal
temps. PoPs will remain mostly in the chc range, and QPF doesn't
look heavy.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 230 PM EDT Sunday: An upper trough will swing thru the area
Thursday, just as yet another reinforcing trough dives into the
mean eastern CONUS trough across the Midwest. This wave will be
much slower to ride thru the mean trough, not reaching our area
until Friday night or Saturday. Meanwhile, a subtropical ridge
will strengthen and expand slightly westward along the East Coast,
keeping a light, yet moist, southerly to southwesterly flow atop
the forecast area thru the medium range. Temps should gradually
return to near normal by the weekend, with continued above climo
PoPs with a largely diurnal trend. Any severe or heavy rain threat
is still too uncertain to mention in the HWO at this time.

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
At KCLT and elsewhere: Cold front settling thru the area from
N to S this afternoon will be the focus for SHRA/TSRA. This
warrants TEMPOs early in the period at all sites except KAND,
where slightly lower modeled coverage warrants only VCTS. Brisk
gusts are possible with TSRA near KGSP/KGMU/KCLT where there is
better dry midlevel air to begin with. Winds will shift into N
half behind the front in general; may waver back and forth across
270 at KCLT for a time. Mountain valley fog expected tonight and
MVFR fcst near daybreak at KAVL; can't rule fog out at any other
site particularly where a direct TS hit occurs today, but not
confident enough to mention. Suppressed convection in the subsident
post-frontal airmass on Monday; only low-VFR cu mentioned in TAFs.

Outlook: Widespread precip likely Monday night into Tuesday with
cold-air damming event, with a few TSRA possible as well. Diurnal
SHRA/TSRA expected Wednesday thru Friday, but confidence limited by
differing depictions of stalled front near the SE coast. Fog/low
stratus will be possible each morning, particularly for areas
primed by rainfall the previous evening.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High  87%     High 100%     High  85%     High 100%
KHKY       High  99%     High 100%     High 100%     High 100%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High 100%     High 100%     High 100%     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 are available at
the following link:

www.weather.gov/gsp/aviation

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

SYNOPSIS...DEO
NEAR TERM...Wimberley
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...Wimberley

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
430 AM EDT Sun Aug 1 2021

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-020830-
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 NC-
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-Union SC-Chester-Greenwood-
430 AM EDT Sun Aug 1 2021

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

.DAY ONE...Today and tonight.

Scattered thunderstorms are expected across the area today. A few of
the storms will be strong to possibly even severe. Strong, gusty
winds, possibly damaging, will be the main threat. Cloud-to-ground
lightning and brief, heavy rainfall is possible with any storm.

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

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
214 PM EDT Sun Aug 1 2021

NCZ036-056-011845-
Iredell NC-Catawba NC-
214 PM EDT Sun Aug 1 2021

...A STRONG THUNDERSTORM WILL IMPACT EASTERN CATAWBA AND SOUTHERN
IREDELL COUNTIES UNTIL 245 PM EDT...

At 214 PM EDT, Doppler radar was tracking a strong thunderstorm 10
miles southwest of Statesville, or near Catawba, moving southeast at
30 mph.

Locations to be impacted include...
Mooresville, Troutman, Claremont, Catawba, Lake Norman, Lake Norman
State Park, Lookout Shoals Lake, Conover, Sherrills Ford and Bandys.

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

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm may intensify, so be certain to monitor local radio and tv
stations, as well as local cable tv outlets for additional
information and possible warnings from the National Weather Service.

Lake Norman is in the path of this storm. Cloud to ground lightning
and gusty winds will create dangerous boating conditions.
Move to shore immediately.

&&

LAT...LON 3552 8074 3552 8090 3565 8114 3574 8124
      3579 8119 3580 8113 3579 8113 3578 8111
      3581 8108 3581 8106 3571 8078
TIME...MOT...LOC 1814Z 293DEG 25KT 3569 8103

MOORE

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
356 PM EDT Sun Aug 1 2021

SCZ003-006-007-012030-
Greenville Mountains SC-Spartanburg SC-Greater Greenville SC-
356 PM EDT Sun Aug 1 2021

...A STRONG THUNDERSTORM WILL IMPACT NORTHEASTERN GREENVILLE AND
NORTHWESTERN SPARTANBURG COUNTIES UNTIL 430 PM EDT...

At 355 PM EDT, Doppler radar was tracking a strong thunderstorm 12
miles south of Columbus, or near Campobello, moving southeast at 20
mph.

Locations to be impacted include...
Greer, Duncan, Lyman, Wellford, Inman, Tigerville, Lake Robinson, GSP
Airport, Taylors and Paris Mountain State Park.

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

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm may intensify, so be certain to monitor local radio and tv
stations, as well as local cable tv outlets for additional
information and possible warnings from the National Weather Service.

&&

LAT...LON 3494 8238 3506 8244 3512 8222 3507 8198
      3488 8214
TIME...MOT...LOC 1955Z 299DEG 15KT 3506 8217

MOORE

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
410 PM EDT Sun Aug 1 2021

SCZ008-009-013-012045-
York SC-Cherokee SC-Union SC-
410 PM EDT Sun Aug 1 2021

...A STRONG THUNDERSTORM WILL IMPACT SOUTHWESTERN YORK...SOUTHEASTERN
CHEROKEE AND NORTHEASTERN UNION COUNTIES UNTIL 445 PM EDT...

At 410 PM EDT, Doppler radar was tracking a strong thunderstorm 9
miles southeast of Gaffney, or 7 miles west of Hickory Grove, moving
southeast at 15 mph.

Locations to be impacted include...
Hickory Grove, Sharon, Draytonville, Saratt and Cherokee Falls.

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

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm may intensify, so be certain to monitor local radio and tv
stations, as well as local cable tv outlets for additional
information and possible warnings from the National Weather Service.

&&

LAT...LON 3491 8166 3501 8170 3507 8157 3499 8132
      3482 8147 3482 8149 3481 8148 3480 8149
TIME...MOT...LOC 2010Z 299DEG 15KT 3496 8155

MOORE