Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
235 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 2:15pm EDT Tuesday:  Thunderstorms, with a few possibly
reaching severe levels, are anticipated this afternoon and tomorrow
afternoon. 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. Southerly flow will keep dewpoints
and temperatures several degrees above normal. Afternoon MLCAPE
levels will be around 1000 j/kg today and tomorrow, with very little
shear or forcing to help things along.  Still, instability levels
are sufficient for a severe storm or 2 in afternoon heating. High-
res models indicate some uptick in strength of storms Wednesday
afternoon relative to today, possibly due to marginally improved
upper dynamics.  Slow movement of storms today and tomorrow suggest
some chance for isolated flooding if storms linger too long in one
location.

Convection today and tomorrow should fade after sunset.  With high
dewpoints and some areas with recent rain, fog has been forming in
mountain valleys overnight, which is expected again tonight.

&&

.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 MONDAY/...
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 /19Z TUESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Showers and thunderstorms are beginning to
develop all areas this afternoon, and will potentially impact any
airport in the region through 00Z.  Convective instability is a
little higher than previous days, with possibly strong to severe
outflow winds from these storms.  Winds outside of effects of storms
are light to variable, with a south to southwest bias due to surface
high east of the region.  Surface pattern changes little through
Wednesday.  Fog is again expected this morning in the same places
where it occurred this morning, principally mountain valleys.  As
KAVL fell to 1/4sm this morning, will be a little more aggressive on
forecast fog for that location.

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...

            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 100%     High 100%     High  94%     High  95%
KHKY       High 100%     High 100%     High  95%     High  95%
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...WJM
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...WJM

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
614 PM EDT Tue Aug 10 2021

NCZ051-058-102245-
Graham NC-Swain NC-
614 PM EDT Tue Aug 10 2021

...Strong thunderstorms will impact portions of west central Swain
and Graham Counties through 645 PM EDT...

At 614 PM EDT, Doppler radar was tracking strong thunderstorms along
a line extending from 11 miles northwest of Robbinsville to 9 miles
northwest of Andrews. Movement was east at 40 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...
Robbinsville, Town Of Santeetlah, Fontana Village, Lake Santeetlah,
Smoky Mountains-Twentymile Creek, Fontana Lake, Smoky
Mountains-Fontana Area, Tapoco, Cheoah and Deals Gap.

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.

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

&&

LAT...LON 3535 8403 3537 8401 3541 8402 3546 8396
      3547 8392 3552 8388 3553 8382 3556 8377
      3556 8375 3526 8369 3525 8370 3526 8372
      3524 8375 3526 8379 3525 8385 3522 8397
      3523 8400 3531 8402 3531 8404
TIME...MOT...LOC 2214Z 261DEG 33KT 3543 8396 3526 8397

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

CAC

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

NCZ071-072-082-102300-
Union NC-Cabarrus NC-Mecklenburg NC-
628 PM EDT Tue Aug 10 2021

...A strong thunderstorm will impact portions of southwestern
Cabarrus, southeastern Mecklenburg and north central Union Counties
through 700 PM EDT...

At 627 PM EDT, Doppler radar was tracking a strong thunderstorm 9
miles east of Uptown Charlotte, or near Mint Hill, moving northeast
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...
East Charlotte, Mint Hill, Lake Park, Hemby Bridge, Reedy Creek Park,
Harrisburg, Midland, Matthews, The Plaza and Stallings.

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.

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 3508 8064 3519 8082 3533 8068 3522 8049
TIME...MOT...LOC 2227Z 219DEG 8KT 3520 8068

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

CAC

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