Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
618 PM EDT Wed Aug 4 2021

.SYNOPSIS...
A stationary front will remain stalled along the southeast United
States coast through early Saturday before dissipating. Meanwhile,
the trough situated over the eastern United States will gradually
lift northeast. High pressure builds in briefly Friday across the
southeast before another trough tracks across the region. Diurnal
shower and thunderstorm chances will continue this week but will be
somewhat limited by lack of moisture. Friday night into Saturday
looks like the best chance for showers and thunderstorms as the
trough tracks east across the forecast area.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 6 pm EDT Wednesday: Water vapor imagery shows a deep upper-
level trough axis approaching the base of the southern Appalachians
early this evening. A vorticity lobe in the base of the trough will
be the main forcing mechanism for the next few hours, but surface-
based instability will be limited mainly to the southwest part of
the area, especially the Upper Savannah River region, until a few
hours after sundown. The PoP gradient has been sharpened up from
this higher PoP area to much lower values farther north and east
this evening. Despite the continued upper support with the passage
of the vorticity lobe through 06Z, the convection-allowing models
have limited response through the overnight, although light upslope
showers in easterly boundary layer flow cannot be ruled out along
the Blue Ridge escarpment.

Otherwise, lingering surface high pressure to the north and
northeast will provide mostly northeasterly surface winds through
tomorrow. This will result in even less moisture in profiles, a
drier boundary layer, and with upper support moving off to the east,
any PoPs will be limited to the western mountains during peak
heating. Max temperatures should rebound at least a category with a
bit better insolation.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SUNDAY/...
As of 200 PM EDT Wednesday: The stationary front along the SE CONUS
should dissipate early Saturday. Meanwhile, northeast Georgia and
the Carolinas will be sandwiched between troughs Thursday night into
Friday. A high pressure ridge in the western Atlantic should nudge
into the southeastern CONUS Friday. With this synoptic pattern in
place at the start of the short term period, moisture should be
limited across the CWA as PWAT values remain low Thursday night into
most of Friday. Therefore, have capped diurnal showers and
thunderstorms to a slight chance to chance during this time frame.
The ridge of high pressure extending into the area will be forced to
the south and east as a trough approaches from the west Friday
evening into Saturday. PWATs increase during this time frame as the
trough tracks east towards the forecast area. Both the GFS and ECMWF
have come into better agreement in regards of the timing and
behavior of the trough this weekend. At this time, Friday night into
Saturday looks like the best chance to see showers and thunderstorms
from this upper-level trough due to the increased moisture the
system brings. Capped PoPs from a high end chance to low end likely
across the CWA. Sunday this trough should lift northeast into the
northeastern CONUS allowing high pressure in the western Atlantic to
build in from the south. In response to this ridge building back
into the area, PWATs should slightly decline again Sunday. As a
result, capped PoPs across the CWA to a slight chance. Highs Friday
and Saturday should be near normal to a few degrees below normal.
Sunday highs return to above normal.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
As of 200 PM EDT Wednesday: High pressure could continue to build in
across the Southeast Sunday night into Monday. The ECMWF shows this,
however the GFS hints at a small area of low pressure forming across
the Deep South and tracking into the Carolinas during this time
frame. Tuesday into Wednesday remains even more uncertain as models
continue to diverge on the overall synoptic pattern. The ECMWF keeps
the ridge in place for the second half of the extended period while
the GFS has the low dissipating early Tuesday with high pressure
retreating east as a trough digs from southern Canada into the
northern United States. With model disagreement throughout much of
the extended period, decided to keep diurnal shower and thunderstorm
chances in the forecast, but capped PoPs to a slight chance to
chance. Highs throughout the extended period should be above climo
and much warmer compared to what we are seeing now.

&&

.AVIATION /22Z WEDNESDAY THROUGH MONDAY/...
At KCLT and elsewhere: Surface high pressure will remain to the
north to northeast of the region, providing generally light easterly
to northerly winds. The pressure gradient remains weak enough to
lead to calm or variable winds at times overnight. Showers look to
be restricted to the mountains this evening, with a VCSH mentioned
only at KAVL. Thursday appears to have slightly lesser chances for
showers or thunderstorms, which remain too low in probability to be
worth mentioning in any of the TAFs. With northeasterly winds, some
low end VFR cigs will be possible at all TAF sites this evening. Fog
and low stratus will also be possible in fog-prone mountain valleys
overnight, only affecting the KAVL aerodrome. Cigs may scatter a bit
more with mixing on Thursday.

Outlook: Typical summertime diurnal convection will redevelop over
the area into the weekend. Fog and low stratus will be possible each
morning, particularly for the mtn valleys and areas primed by
rainfall from the previous evening.

Confidence Table...

            22-04Z        04-10Z        10-16Z        16-18Z
KCLT       High 100%     High 100%     High  97%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     Med   64%     High 100%
KHKY       High 100%     High 100%     High  95%     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...AP
NEAR TERM...HG/WJM
SHORT TERM...AP
LONG TERM...AP
AVIATION...HG/WJM

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
445 PM EDT Wed Aug 4 2021

GAZ010-017-018-026-NCZ033-048>053-058-059-062>065-SCZ001-002-004-
052045-
Rabun-Habersham-Stephens-Franklin-Avery-Madison-Yancey-Mitchell-
Swain-Haywood-Buncombe-Graham-Northern Jackson-Macon-
Southern Jackson-Transylvania-Henderson-Oconee Mountains-
Pickens Mountains-Greater Oconee-
445 PM EDT Wed Aug 4 2021

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

.DAY ONE...Tonight.

There remains the chance of scattered showers and a few
thunderstorms into this evening. Any storm will be capable of
producing brief heavy rain and occasional cloud-to-ground lightning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

GAZ028-029-NCZ035>037-056-057-068>072-082-501>510-SCZ003-005>014-019-
052045-
Hart-Elbert-Alexander-Iredell-Davie-Catawba-Rowan-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-Greenville Mountains-Greater Pickens-
Greater Greenville-Spartanburg-Cherokee-York-Anderson-Abbeville-
Laurens-Union SC-Chester-Greenwood-
445 PM EDT Wed Aug 4 2021

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

.DAY ONE...Tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
213 PM EDT WED AUG 04 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0455 AM     TSTM WND DMG     5 NNE HARMONY           36.02N 80.74W
08/01/2021                   IREDELL            NC   EMERGENCY MNGR

            EMERGENCY MNGR REPORTED SEVERAL LARGE TREES DOWN ON N
            MEADOW RD.

&&

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
313 PM EDT Wed Aug 4 2021

NCZ051-042000-
Swain NC-
313 PM EDT Wed Aug 4 2021

...HEAVY RAIN SHOWERS WILL IMPACT WEST CENTRAL SWAIN COUNTY UNTIL
400 PM EDT...

At 311 PM EDT, Doppler radar was tracking a series of heavy rain
showers affecting the area about 12 miles north of Robbinsville, or
near Smoky Mountains-Twentymile Creek. These showers were nearly
stationary, or redeveloping in place.

Locations to be impacted include...
Smoky Mountains-Twentymile Creek, Fontana Village, Smoky Mountains-
Fontana Area, Fontana Lake, Deals Gap and Tapoco. Stream levels will
rise rapidly along Round Mountain Branch and Twentymile Creek.

Very heavy rainfall rates up to 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 3548 8391 3552 8388 3553 8382 3556 8377
      3556 8372 3552 8369 3545 8379 3545 8380
      3544 8381 3545 8385 3545 8386 3546 8387
      3547 8390 3545 8393 3546 8395
TIME...MOT...LOC 1911Z 106DEG 1KT 3550 8381

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
526 PM EDT Wed Aug 4 2021

GAZ010-017-042215-
Rabun GA-Habersham GA-
526 PM EDT Wed Aug 4 2021

...HEAVY RAIN SHOWERS WILL IMPACT NORTHWESTERN HABERSHAM AND WESTERN
RABUN COUNTIES UNTIL 615 PM EDT...

At 523 PM EDT, Doppler radar indicated heavy rain showers along a
line extending from 10 miles east of Hiawassee to 7 miles northwest
of Clarkesville, and moving very slowly east at 5 mph.

Locations to be impacted include...Lake Burton, Seed Lake and
Batesville. Rapid stream rises are expected along the headwaters and
tributaries feeding the Soquee River, as well as Wildcat Creek,
South Fork Moccasin Creek, and Chastain Creek.

Heavy rainfall rates up to 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 3482 8365 3484 8366 3488 8366 3491 8363
      3492 8360 3494 8360 3495 8355 3499 8355
      3499 8346 3463 8353 3465 8366 3466 8366
      3467 8365 3471 8364 3473 8362 3477 8363
      3480 8368
TIME...MOT...LOC 2123Z 262DEG 5KT 3493 8358 3465 8364

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
624 PM EDT Wed Aug 4 2021

GAZ017-042300-
Habersham GA-
624 PM EDT Wed Aug 4 2021

...HEAVY RAIN SHOWERS WILL IMPACT SOUTHERN HABERSHAM COUNTY UNTIL
700 PM EDT...

At 623 PM EDT, Doppler radar was tracking a cluster of heavy showers
near Clarkesville, moving southeast at 15 mph.

Locations to be impacted include...
Clarkesville, Cornelia, Baldwin, Demorest, Mount Airy, Alto and
Raoul.

Very heavy rainfall rates up to 2 inches per hour will be possible in
these areas.

LAT...LON 3454 8362 3456 8363 3459 8364 3469 8353
      3460 8340 3459 8340 3448 8346 3449 8354
      3443 8362 3452 8366
TIME...MOT...LOC 2223Z 320DEG 13KT 3457 8354

CSH