Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
757 PM EDT Tue Aug 10 2021

.SYNOPSIS...
High pressure will persist off the Southeast coast, resulting in
a typical summertime pattern across the region this week. Abundant
moisture ahead of an approaching cold front will enhance coverage
of showers and thunderstorms, mainly in the afternoons and evenings.
The front is forecast to stall over the area this weekend,
maintaining good chances for rainfall.  A tropical system could add
to our rainfall in the first half of next week.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 730 PM EDT Tuesday: Thunderstorms have pushed out of the
mountains and into the Piedmont where DCAPEs are a little higher,
and we're seeing stronger wind gusts to go with them. Near term
update has tried to account for radar trends but CAMs are, as usual,
not handling the pulse convection well so have made a bunch of hand
edits. Highs today outperformed the forecast across the Piedmont and
so had to make adjustments for hourly trends into the night. Other
changes are for aviation-related parameters and expect that we
should see typical mountain valley fog overnight as guidance is
starting to hit that harder with recent updates.

Otherwise, a large upper low remains in place centered over Central
Canada, with a circulation that extends marginally down into the
Southern States. Dynamics over the GSP area are quite weak, with
scarcely any deep layer shear. Upper and lower high pressure lies
off the Atlantic Coast, giving light to variable mostly southerly to
southwesterly flow to the region. Synoptic features have small
changes over the next 24 hours, with upper North American low making
some slight eastward progress.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
As of 100 PM EDT Tuesday: A deep trough over the upper Midwest will
persist through the short term, while the Bermuda high will nudge
slightly westward in response to a building subtropical ridge over
the eastern CONUS.  On Thursday, as the ever-weakening boundary
draped across the Southeast pushes northward, southerly surface
flow will strengthen, advecting a plume of moisture into the region.
PWATs should climb well into the 1.7"+ range by Thursday afternoon.
With SBCAPE in excess of 1000 J/kg across the Piedmont and Upstate,
we'll be in store for another round of diurnally-driven pulse
convection.  In the absence of any discernible lifting mechanism,
and with midlevel drying promoting higher LFCs, widespread
convection should be somewhat suppressed.  Still, we're likely to
see isolated to scattered showers and thunder across the forecast
area, and with increasingly dry midlevels, a few of these storms
could produce downbursts.  The latest guidnace doesn't suggest
surface-to-700mb delta-theta-e values will be quite high enough
for a serious microburst threat, but the potential for some gusty
straight-line winds is there.

Friday will be a similar, if somewhat enhanced, scenario.  Guidance
depicts a 500mb shortwave rotating across the deeper trough over
the course of the day, resulting in increased DPVA and driving
increased PoPs beginning Friday afternoon.  Coverage of convection
should be enhanced on Friday afternoon as well - model consensus
points to SBCAPE in the 800-1200 J/kg range, and profiles should
be moister in the midlevels than on Thursday, making them more
conducive to convective initiation.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 145 PM EDT Tuesday: PoPs continue to increase into Saturday as
a front pushes into the southeast CONUS.  By now, moister profiles
and falling heights should allow for widespread rainfall ahead
of the front; although cloud cover should be building Saturday,
somewhat hindering destabilization, it's likely we'll see some
embedded thunder in the afternoon.  Once again, localized heavy
rain will present a flooding concern.  As the frontal zone reaches
us on Sunday, we'll ramp up to ever-higher PoPs in the morning.

Early next week, all the global models agree we'll come under
the influence of PTC 6.  Although there remain significant track
differences between models and to some extent from run to run,
the general consensus is that the system will track up the west
Florida coast before turning more northward.  What local impacts
we'll face is unclear, though heavy rain and ensuing flooding
is certainly a possibility, especially as the extensive rainfall
we'll have received prior to PTC 6's arrival should have raised
soil moisture and primed the ground for flash floods.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: TSRA along and S of the I85 corridor
has pushed away from KGSP and generally KCLT as well, but have kept
VCTS for another hour at KCLT. Should still see convection in
vicinity of KAND. Otherwise TAFs should generally be clear of
convection for the evening barring a sunset surprise that will have
to be monitored. Expect mountain valley fog to form and have kept
previous trends at KAVL but added TEMPO for VLIFR conditions in the
pre-dawn hours. Winds should remain generally SW through the period
5kt or less, except in any TS that might develop tomorrow afternoon.
Expect another round of diurnal convection tomorrow, with greater
coverage than today, so kept trend of PROB30 for all sites tomorrow.

Outlook: Diurnal shower/thunderstorm activity remains in the
forecast the rest of the week.  Fog and low stratus will be possible
each morning, particularly over mountain valleys and areas primed
by rainfall from the previous evening.

Confidence Table...

            00-06Z        06-12Z        12-18Z        18-00Z
KCLT       High 100%     High 100%     High  99%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     Low   44%     Med   76%     Med   77%
KHKY       High 100%     High  95%     High  90%     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...TDP/WJM
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...TDP

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
522 AM EDT Tue Aug 10 2021

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-110400-
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-
522 AM EDT Tue Aug 10 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 will develop across the area today, with the
greatest coverage during the afternoon. Any of these storms will be
capable of dangerous cloud-to-ground lightning as well as heavy
downpours. Localized flash flooding may result.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

Wimberley

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
630 PM EDT Tue Aug 10 2021

SCZ007-008-013-102300-
Cherokee SC-Union SC-Spartanburg SC-
630 PM EDT Tue Aug 10 2021

...A strong thunderstorm will impact portions of east central
Spartanburg, southwestern Cherokee and north central Union Counties
through 700 PM EDT...

At 630 PM EDT, Doppler radar was tracking a strong thunderstorm 10
miles south of Gaffney, or near Pacolet Mills, moving east at 20 mph.

HAZARD...Wind gusts up to 50 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Spartanburg, Pacolet, Cowpens, Jonesville, Pacolet Mills, Croft State
Park, Cedar Springs, Roebuck and Thicketty.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3488 8196 3501 8189 3503 8174 3502 8160
      3483 8167
TIME...MOT...LOC 2230Z 281DEG 18KT 3493 8172

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH

CAC

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
641 PM EDT Tue Aug 10 2021

SCZ001-002-004-005-102315-
Pickens Mountains SC-Greater Pickens SC-Greater Oconee SC-
Oconee Mountains SC-
641 PM EDT Tue Aug 10 2021

...A strong thunderstorm will impact portions of west central Pickens
and east central Oconee Counties through 715 PM EDT...

At 641 PM EDT, Doppler radar was tracking a strong thunderstorm 6
miles northeast of Walhalla, or 4 miles southwest of Lake Keowee,
moving east at 10 mph.

HAZARD...Winds in excess of 40 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Seneca, Walhalla, Salem, Lake Keowee, Keowee Toxaway State Park,
Westminster and Nine Times.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

If on or near Lake Keowee, get out of the water and move indoors or
inside a vehicle. Remember, lightning can strike out to 10 miles
from the parent thunderstorm. If you can hear thunder, you are close
enough to be struck by lightning. Move to safe shelter now! Do not
be caught on the water in a thunderstorm.

&&

LAT...LON 3468 8313 3491 8307 3494 8280 3464 8290
TIME...MOT...LOC 2241Z 272DEG 9KT 3482 8296

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH

CAC

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
654 PM EDT Tue Aug 10 2021

NCZ051-062-102345-
Swain NC-Macon NC-
654 PM EDT Tue Aug 10 2021

...A strong thunderstorm will impact portions of northwestern Macon
and south central Swain Counties through 745 PM EDT...

At 653 PM EDT, Doppler radar was tracking a strong thunderstorm 12
miles southwest of Bryson City, or 7 miles northeast of Nantahala
Lake, moving northeast at 5 mph.

Other strong thunderstorms over Cherokee and Graham counties may
affect the western part of Macon County through 730 pm.

HAZARD...Winds in excess of 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Nantahala Lake, Wesser, Almond, Burningtown, Kyle, Nantahala, Wayah
Bald, Aquone and Luada.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 3518 8373 3519 8371 3520 8371 3520 8372
      3521 8373 3523 8369 3525 8370 3528 8368
      3530 8370 3532 8369 3538 8354 3535 8348
      3519 8340 3516 8373
TIME...MOT...LOC 2253Z 242DEG 5KT 3528 8356

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

MOORE

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
707 PM EDT Tue Aug 10 2021

NCZ071-072-082-102345-
Union NC-Cabarrus NC-Mecklenburg NC-
707 PM EDT Tue Aug 10 2021

...A strong thunderstorm will impact portions of southwestern
Cabarrus, southeastern Mecklenburg and northwestern Union Counties
through 745 PM EDT...

At 707 PM EDT, Doppler radar was tracking a strong thunderstorm 8
miles east of Uptown Charlotte, or near Mint Hill. This storm was
nearly stationary.

HAZARD...Winds in excess of 40 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
East Charlotte, Matthews, Mint Hill, Indian Trail, Stallings,
Harrisburg, Lake Park, Hemby Bridge, University City and Reedy Creek
Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3507 8076 3530 8078 3537 8062 3506 8051
TIME...MOT...LOC 2307Z 255DEG 3KT 3521 8069

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH

CAC

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
801 PM EDT Tue Aug 10 2021

GAZ028-SCZ004-006-010>012-019-110030-
Hart GA-Greater Oconee SC-Laurens SC-Anderson SC-Abbeville SC-
Greenwood SC-Greater Greenville SC-
801 PM EDT Tue Aug 10 2021

...Strong thunderstorms will impact portions of central Hart, west
central Laurens, southeastern Greenville, Anderson, northern
Abbeville, southeastern Oconee and northwestern Greenwood Counties
through 830 PM EDT...

At 801 PM EDT, Doppler radar was tracking strong thunderstorms along
a line extending from 13 miles northwest of Laurens to 5 miles south
of Anderson to 7 miles north of Hartwell. Movement was south at 25
mph.

HAZARD...Wind gusts up to 50 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Anderson, Hartwell, Homeland Park, Belton, Northlake, Honea Path,
Ware Shoals, Reed Creek, Due West and Iva.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with these storms and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

If on or near Lake Hartwell, get out of the water and move indoors
or inside a vehicle. Remember, lightning can strike out to 10 miles
from the parent thunderstorm. If you can hear thunder, you are close
enough to be struck by lightning. Move to safe shelter now! Do not
be caught on the water in a thunderstorm.

&&

LAT...LON 3427 8275 3429 8277 3428 8280 3432 8305
      3458 8299 3459 8260 3467 8221 3438 8214
      3426 8268
TIME...MOT...LOC 0001Z 007DEG 23KT 3458 8224 3444 8262 3447 8292

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH

CAC

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
804 PM EDT Tue Aug 10 2021

GAZ010-017-110030-
Rabun GA-Habersham GA-
804 PM EDT Tue Aug 10 2021

...A strong thunderstorm will impact portions of northwestern
Habersham and western Rabun Counties through 830 PM EDT...

At 803 PM EDT, Doppler radar was tracking a strong thunderstorm 10
miles southeast of Hiawassee, or near Lake Burton, moving southeast
at 10 mph.

HAZARD...Winds in excess of 40 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Clayton, Mountain City, Tiger, Lake Rabun, Lake Burton, Lakemont,
Black Rock Mountain State Park, Batesville and Seed Lake.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

If on or near Lake Burton, Nacoohe Lake, and Lake Rabun, get out of
the water and move indoors or inside a vehicle. Remember, lightning
can strike out to 10 miles from the parent thunderstorm. If you can
hear thunder, you are close enough to be struck by lightning. Move
to safe shelter now! Do not be caught on the water in a thunderstorm.

&&

LAT...LON 3482 8365 3484 8366 3488 8366 3490 8363
      3491 8363 3492 8360 3494 8360 3495 8355
      3498 8355 3493 8336 3476 8342 3463 8359
      3471 8364 3473 8362 3476 8363 3480 8368
TIME...MOT...LOC 0003Z 324DEG 7KT 3486 8360

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH

CAC