Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
259 PM EDT Thu Aug 19 2021

.SYNOPSIS...
A weak upper trough and abundant moisture will continue across the
region into Friday leading to scattered afternoon and evening
showers and thunderstorms. Saturday an upper-level low will meander
around the Ohio Valley and Mid-Atlantic region before lifting
northeast into New England late this weekend into early next week as
a ridge of high pressure to the south nudges eastward. This should
lead to drier conditions for the weekend with only isolated showers
and thunderstorms during the afternoon and evening hours expected.
Highs will remain above climo this week into next week.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of 2:45pm EDT Thursday:  Round of typical diurnal thunderstorms
is underway this afternoon, expected to die out after dark.  Storms
are being enhanced by the passage of a weak upper wave. This shows
nicely as updraft strength in hi-res models. This wave will have
most of its energy east of the region by tomorrow, and while some
thunder will still be possible, the coverage and intensity will be
much reduced from today.  For today, forcing from the wave might
give some severe storms today, despite only 500-1000 j/kg of MLCAPE.
Bulk shear and hodographs are unimpressive, with pulse severe wind
gusts the main threat.  Storm motion is also eastward at 10 to
20kts, which should reduce the risk from hydro issues.  Should mid
and upper clouds clear behind weak surface boundary ahead of upper
wave later tonight, fog could become an issue overnight as surface
layer remains very moist from recent rains, but this is not clear.
Fading tropical air mass will have highs and lows near to a couple
degrees above normal tomorrow.  Winds are fairly light around weak
frontal boundary, and will be lighter on Friday as surface high
behind boundary moves in.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 215 PM EDT Thursday...A ridge of high pressure will continue
to dominate across the southern United States through the short term.
Meanwhile an upper-level closed low will meander around the Ohio
Valley and Mid-Atlantic region Friday night into Saturday. This low
will be forced to lift northeast into New England as the ridge of
high pressure in the southern CONUS nudges eastward Saturday night
into early Monday. As a result of this ridge pushing east into the
western Carolinas and northeast Georgia, flow will be mainly
northerly and northwesterly. This will lead to limited moisture
across the CWA this weekend. Capped PoPs to a slight chance to
chance for the entire period as only isolated showers and
thunderstorms look possible. Highs this weekend should be a couple
degrees above climo.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
As of 215 PM EDT Thursday...The closed low keeps lifting northeast
out of New England into Nova Scotia during the first half of the
extended term forecast period. This will allow the ridge to remain
over the southeastern CONUS through the middle of next week. Towards
the end of the forecast period, this ridge should start to
retrograde back west of the CWA. Meanwhile, a surface trough looks
to linger along the Southeast coast throughout the extended. Monday
and Tuesday are looking like the drier days as the eastern periphery
of the ridge will remain over the area. Capped PoPs to a slight
chance to chance for this reason. Wednesday into Thursday moisture
associated with this trough could push further inland as the high
retreats west. This would increase the moisture influx. Both the GFS
and ECMWF have PWAT values increasing Wednesday into Thursday. As a
result, have PoPs at chance for the end of the forecast period.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
At KCLT and elsewhere:  Thunderstorms now spreading across the area
from west to east.  Expect a typical diurnal pattern with storms
dying out just after sunset.  Upper trough crossing the area will
assist storm development today with some severe.  Weak surface
boundary has generally SW winds of 5 to 10 kts.  As this boundary
moves eastward, surface high comes in, and winds become light and
VRB overnight, becoming more NW to northerly on Friday.  Opted to
keep in some mention of fog at all locations as some possible
clearing overnight above a still moist surface layer and light
winds, will create good conditions for fog formation at some level.
For KCLT, have kept in a PROB30 for thunder tomorrow afternoon,
though storms will be much more widely scattered than today.

Outlook: A typical, diurnal summertime convective pattern is
expected to prevail into early next week, with coverage scattered at
best. Mtn valley low stratus and fog will be possible each morning.

Confidence Table...

            12-18Z        18-24Z        00-06Z        06-12Z
KCLT       High 100%     High 100%     High 100%     High  89%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High  92%     High 100%     High  84%
KHKY       High 100%     High 100%     High  95%     Med   76%
KGMU       High 100%     High 100%     High 100%     High  95%
KAND       High 100%     High 100%     High 100%     High  95%

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...AP
NEAR TERM...WJM
SHORT TERM...AP
LONG TERM...AP
AVIATION...WJM

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
554 PM EDT Thu Aug 19 2021

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-202200-
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-
554 PM EDT Thu Aug 19 2021

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

.DAY ONE...Tonight.

Scattered thunderstorms will continue to move east across the
Upstate, foothills, and Piedmont this afternoon and early this
evening. Some storms will become strong to severe, producing frequent
cloud- to- ground lightning, damaging wind gusts, and hail. Locally
heavy rainfall is also possible. The storms should end by mid-evening
near or just east of the Charlotte metro area.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Hazardous weather is not expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

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Special Weather Statement
National Weather Service Greenville-Spartanburg SC
550 PM EDT Thu Aug 19 2021

SCZ009-014-192215-
York SC-Chester SC-
550 PM EDT Thu Aug 19 2021

...A strong thunderstorm will impact portions of northeastern Chester
and southeastern York Counties through 615 PM EDT...

At 550 PM EDT, Doppler radar was tracking a strong thunderstorm 5
miles south of Rock Hill, or near Lesslie, moving east at 15 mph.

HAZARD...Wind gusts up to 50 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...
Rock Hill, Lesslie, Catawba and Edgemoor.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

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 3490 8088 3487 8088 3486 8087 3484 8087
      3483 8090 3482 8090 3479 8088 3474 8088
      3479 8119 3494 8117 3496 8093 3497 8088
      3496 8087 3492 8086
TIME...MOT...LOC 2150Z 271DEG 12KT 3487 8099

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH

RWH

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
600 PM EDT Thu Aug 19 2021

NCZ068-070-SCZ008-009-192230-
Gaston NC-Cleveland NC-York SC-Cherokee SC-
600 PM EDT Thu Aug 19 2021

...Strong thunderstorms will impact portions of southeastern
Cleveland, Gaston, central York and northeastern Cherokee Counties
through 630 PM EDT...

At 559 PM EDT, Doppler radar was tracking strong thunderstorms along
a line extending from 9 miles west of Gastonia to 4 miles west of
York. Movement was northeast at 20 mph.

HAZARD...Wind gusts up to 50 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...
Gastonia, York, Rock Hill, Kings Mountain, Mt Holly, Belmont,
Bessemer City, South Gastonia, Tega Cay and Clover.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

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 3498 8095 3488 8144 3524 8145 3541 8117
      3540 8100 3532 8099 3527 8102 3517 8100
      3515 8101 3515 8104 3514 8105 3511 8103
      3509 8106 3506 8106 3504 8104 3509 8096
TIME...MOT...LOC 2159Z 242DEG 20KT 3523 8133 3498 8130

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH

RWH