Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
222 PM EDT Mon Aug 9 2021

.SYNOPSIS...
High pressure will persist off the Southeast coast, resulting in
a typical summertime pattern across the region through the week.
An increase in moisture will occur in the middle of the week
ahead of an approaching cold front, which will enhance coverage
of showers and thunderstorms across the region, mainly in the
afternoons and evenings. This front is forecast to become stationary
from west to east across our region through the weekend which will
continue scattered to numerous showers and thunderstorms.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 215 PM EDT Monday: The arrival of a weak shortwave trough
has induced modest height falls today, resulting in weak synoptic
forcing and widespread cloud cover as anticipated.  Convection is
underway at many locations across the NC foothills and Piedmont,
though for now it remains unremarkable on radar.

Over the last several hours, CAMs have trended upward in terms of
convective coverage across the Piedmont.  Despite scattered clouds
today, destabilization has occurred virtually everywhere, with the
SC Upstate in particular boasting SBCAPE values of 1500-2000 J/kg.
Consequently, the CAMs' output seems reasonable, and we can expect
isolated to scattered showers and thunderstorms persisting into
the early evening before dying down after nightfall.  Though a
stray severe cell cannot be ruled out, the lack of appreciable
shear suggests we'll see mainly nondescript, disorganized pulse
convection.

Overnight, synoptic forcing continues as a weak frontal boundary
approaches from the west.  This should maintain at least scattered
high clouds overnight, which will somewhat hinder radiative cooling.
Nonetheless, patchy fog is expected to develop in mountain valleys
in the hours before sunrise Tuesday.  Following this, the frontal
boundary should begin to push across the mountains by late morning;
although not timed right at peak heating, we should see enough
destabilization for scattered showers and some embedded thunder by
late morning/early afternoon Tuesday.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 100 PM EDT Monday...The pattern continues to be dominated by a
stg subTrop engulfing the southeast states thru the period. A weak
sfc bndry will work in underneath the ridge and may provide a better
focusing zone for deeper convec...mainly across the nrn zones and
the NC mtns. Soundings show weak sw/ly flow thru the column and
increasing saturation thru the period. This will bring PWATs to near 2
inches both days and increase the risk for isol hydro issues with
any storms that linger or back-build over the same areas. Not
anticipating much of a severe threat as the storm mode generally
remains pulse, but a few cells could become quite strong each
afternoon and produce sigfnt outflows. Max and min temps will remain
at or a bit abv normal thru the period.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 200 PM EDT Monday...Confidence in the ext range remains abv
average as the op models agree well with the evolution of the mean
pattern. Ensemble spread is low, which is fairly common with this
type of warm season setup. Still anticipate the subTrop high to
remain strong beginning the period with some breakdown, or weakness,
occuring Fri thru the weekend as an h5 trof swings across the Glakes
and Oh Valley regions. This will allow a weak sfc bndry to advance
toward the area Sat, which will maintain abv climo PoPs across the
higher terrain and the northern zones. Surface based instability
looks to remain limited with generally arnd 1500 J/kg of narrow CAPE
developing each afternoon per the latest GFS profiles. Weak flow
also continues thru the column, which will limit the convec mode to
diurnal pulse or outflow driven mutli-cell. Some minor hydro issues
could develop over the weekend, but before that, mid-level dry air
advec from the north will limit precip rates on Fri. Max and min
temps remain a little abv normal thru Sat with a lowering trend
probable on Sun due to enhanced cloud cover associated with a sfc
bndry sagging in from the north.

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
At KCLT and Elsewhere: Convection has already begun east of the
Blue Ridge Escarpment and across the NC foothills.  Scattered
showers and thunder should continue through this evening,
with enough confidence to include TEMPOs for TSRA at KCLT, and
VCTS/VCSH elsewhere.  Should maintain scattered to broken VFR
low clouds through the evening.  Light winds should continue
out of the south/southwest for the duration of the TAF period.
Despite some mid/high clouds lingering overnight, KAVL and KHKY
feature a chance for some fog/low stratus in the predawn hours,
with KHKY never dropping below VFR restrictions, and KAVL at
least briefly dropping to LIFR restrictions.  Tomorrow, should
see preconvective clouds start to develop by 15Z or so.

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  85%
KGSP       High 100%     High 100%     High 100%     High  85%
KAVL       High 100%     High 100%     High  82%     Med   76%
KHKY       High 100%     High 100%     High 100%     High 100%
KGMU       High 100%     High 100%     High 100%     High  85%
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...MPR/PM
SHORT TERM...SBK
LONG TERM...SBK
AVIATION...MPR/PM

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
419 PM EDT Mon Aug 9 2021

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-102030-
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-
419 PM EDT Mon Aug 9 2021

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

.DAY ONE...Tonight.

Isolated showers and thunderstorms will continue across portions of
the area into this evening. Cloud-to-ground lightning and heavy
rainfall are the main potential impacts.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
412 PM EDT Mon Aug 9 2021

SCZ014-092100-
Chester SC-
412 PM EDT Mon Aug 9 2021

...HEAVY RAIN SHOWERS WILL IMPACT SOUTHERN CHESTER COUNTY UNTIL 500
PM EDT...

At 409 PM EDT, Doppler radar was tracking a series of heavy rain
showers about 12 miles north of Winnsboro, or 4 miles east of
Blackstock, moving east at 5 mph. These showers will redeveloping in
place.

Locations to be impacted include...Blackstock, Great Falls and
Cornwell. Rapid rises are also expected along Bell Creek in the
extreme southern Chester County.

Very heavy rainfall rates of 1 to 2 inches per hour will be possible
in these areas. Deep ponding of water will develop in low-lying and
poor drainage areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall may flood areas with poor drainage, such as
ditches and underpasses. Avoid these areas and do not cross flooded
roads. Water levels of small streams may also rise rapidly. Seek
higher ground if threatened by flood waters.

&&

LAT...LON 3456 8118 3463 8118 3470 8102 3461 8092
      3454 8092
TIME...MOT...LOC 2009Z 256DEG 5KT 3455 8107

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
442 PM EDT Mon Aug 9 2021

SCZ014-092130-
Chester SC-
442 PM EDT Mon Aug 9 2021

...HEAVY RAIN SHOWERS WILL IMPACT CHESTER COUNTY UNTIL 530 PM EDT...

At 439 PM EDT, Doppler radar indicated heavy rain showers along a
line extending from 11 miles east of Union to 12 miles northeast of
Winnsboro, and moving east at 5 mph.

Locations to be impacted include...
Chester, Great Falls, Richburg, Lowrys, Chester State Park,
Blackstock, Fishing Creek Reservoir, Leeds and Cornwell. Rapid
stream rises will continue along Bell Creek in extreme southern
Chester County, as well as Grassy Run Branch near Chester, and
Starne Branch north of Leeds.

Very heavy rainfall rates around one inch per hour will be possible
in these areas. Deep ponding of water will develop in low-lying
areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall may flood areas with poor drainage, such as
ditches and underpasses. Avoid these areas and do not cross flooded
roads. Water levels of small streams may also rise rapidly. Seek
higher ground if threatened by flood waters.

&&

LAT...LON 3455 8097 3457 8142 3464 8142 3468 8145
      3472 8145 3473 8149 3476 8145 3478 8145
      3481 8147 3482 8149 3482 8125 3474 8099
      3467 8088 3463 8090 3455 8087
TIME...MOT...LOC 2039Z 260DEG 5KT 3477 8143 3454 8100

HG