Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
220 PM EDT Fri Jul 23 2021

.SYNOPSIS...
Air quality should improve somewhat over the weekend while afternoon
showers and thunderstorms increase in coverage and intensity through
Monday.  A backdoor cold front builds into the forecast area early
next week, bringing more active weather at least through Tuesday.

&&

.NEAR TERM /THROUGH SATURDAY/...
As of 215 PM: Convection beginning to develop along the NC/SC/GA
portion of the Blue Ridge Escarpment. The mountains and the western
Upstate/NE GA remain the most likely locations for convection as
these locations are where the better moisture and instability will
continue. Hot and humid conditions will continue through the
afternoon.

The CAMs and synoptic guidance have generally backed off on the
previous forecast of an uptick in convective activity this evening
and early overnight. That said, isolated showers may linger,
especially in upslope areas, as a moist, low level southerly flow
continues. This flow may also help low clouds to develop near or
just after sunrise. Mountain valley fog and stratus is expected once
again. Lows will be near to slightly above normal.

Heights rise slightly through the period in the northwesterly flow
aloft as a short wave ridge moves over behind a departing trough.
Guidance generally agrees on a lee trough developing and some weak
upper divergence moving through despite the slight increase in
heights. The guidance disagrees on the resulting coverage of
convection. The do agree that the mountains have the best chance,
but some guidance moves the convection off the mountains and across
the piedmont during the late afternoon. Others show only isolated to
low end scattered across the Piedmont. Have gone with the guidance
blend which favors the mountains and foothills, with less coverage
over the Piedmont. Highs will be near to slightly below normal.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
As of 145 PM EDT Friday: With a 500mb ridge entrenched over the
western CONUS, Sunday's opportunity for synoptic forcing will be
severely restricted.  A Bermuda high over the western Atlantic will
help to maintain southerly surface flow...which in turn will help
PWATs ramp up to near 2" by Monday afternoon.  A deep 500mb trough
will spread eastward, though the best DPVA will remain well north of
our CWA.  Global models at least indicate some enhanced QPF response
starting Sunday night and extending through Monday evening, ahead of
a slowly-advancing cold front swooping in from the north.  PoPs on
Sunday afternoon are largely restricted to slight/chance in the
mountains and foothills, as points east appear to be increasingly
well-capped in model soundings, which should inhibit widespread
coverage of convection despite modest SBCAPE of 500-1000 J/kg.
Monday afternoon should fare somewhat better as increased moisture
content, lowered LFCs, and less-stable profiles allow for more
scattered showers and embedded thunderstorms to crop up ahead of the
advancing front.  Activity gradually winds down late Monday night
into Tuesday morning, as the front attempts to clear the region.

For now, have lowered temps a degree or so to more closely match
the latest guidance, which seems to be trending toward slightly
cooler temps for the next few days.  This does little to offset
the unseasonably warm temps forecasted for the weekend.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 200 PM EDT Friday: Upper ridging continues to dominate
the western half of the CONUS.  Following Monday night's frontal
passage we should at least see some improvement in air quality, as
the intrusion of continental air clears out any residual low-level
smoke/haze in the area.  There's a good bit of uncertainty in
the forecast following this fropa, however, as the models haven't
yet reached a consensus on whether the front clears the Carolinas
entirely or stalls for a bit.  What's clear is that the Bermuda high
refuses to budge, and as such we should retain our diurnally-driven
afternoon convection on Tuesday and Wednesday afternoon - something
that the presence of a stalled boundary might work to enhance.
Late week may feature the arrival of another robust midlevel
trough, which would drive a wave of renewed precipitation by
Friday afternoon.  Expect temps to remain at least a few degrees
above normal throughout the medium range forecast.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: Haze has diminished and no longer expect any
restrictions, but 6SM may continue off and on through the day. Low
VFR cumulus has developed and may have a brief cig from time to time
as well. Convection just now developing near the GA/SC portion of
the Blue Ridge escarpment. Expect coverage to be higher in this
general area, but VCTS retained at the Upstate sites and KAVL where
chance is highest. Guidance has trended away from lingering
overnight convection, but isolated -SHRA are possible. Chance too
low for the TAFs. With a moist, southerly flow in place, MVFR
stratocu may develop toward daybreak or with sunrise. Have SCT
coverage developing, but cigs can't be ruled out. Mountain valley
fog and stratus likely again overnight, have included at KAVL as
well. Did not mention convection for Saturday, but this will need to
be added on the next TAF set. Light southeasterly wind this
afternoon becomes light and variable overnight. Light S to SW wind
expected on Saturday.

Outlook: Diurnal thunderstorm chances will steadily increase through
early next week. Early morning fog or low stratus will be possible,
primarily in the mountain valleys.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High 100%     High 100%     High  99%     High  99%
KGSP       High 100%     High 100%     High  98%     High  93%
KAVL       High 100%     Med   74%     Low   58%     High  80%
KHKY       High 100%     High 100%     High  99%     High  87%
KGMU       High 100%     High 100%     High  99%     High  93%
KAND       High 100%     High 100%     High  96%     High  93%

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...MPR
NEAR TERM...RWH
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...RWH

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
342 AM EDT Fri Jul 23 2021

GAZ010-017-018-026-028-029-NCZ033-035-036-048>053-056-058-059-
062>065-068>072-082-501>510-SCZ001>014-019-240745-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Avery-Alexander-
Iredell-Madison-Yancey-Mitchell-Swain-Haywood-Buncombe-Catawba-
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-
342 AM EDT Fri Jul 23 2021

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

.DAY ONE...Today and tonight.

Isolated thunderstorms are possible this afternoon and evening. The
main potential threat will be cloud-to-ground lightning.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

NCZ037-057-240745-
Davie-Rowan-
342 AM EDT Fri Jul 23 2021

This Hazardous Weather Outlook is for piedmont North Carolina.

.DAY ONE...Today and tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
356 PM EDT Fri Jul 23 2021

GAZ010-SCZ001-232030-
Rabun GA-Oconee Mountains SC-
356 PM EDT Fri Jul 23 2021

...A STRONG THUNDERSTORM WITH INTENSE LIGHTNING WILL IMPACT CENTRAL
RABUN AND WEST CENTRAL OCONEE COUNTIES UNTIL 430 PM EDT...

At 355 PM EDT, Doppler radar was tracking a strong thunderstorm with
intense lightning 7 miles southeast of Clayton, moving south at 10
mph.

Locations to be impacted include...
Tallulah Gorge State Park and Long Creek.

In addition to intense lightning, wind gusts up to 40 mph and half
inch hail will be possible in these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Gusty winds can blow down trees that are dead, or that have weakened
root systems. Outdoor furniture and similar items can be tossed
around if not anchored. Seek shelter indoors.

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.

Frequent lightning is occurring with this storm. If outdoors, try to
get indoors or into a hard topped vehicle. Otherwise, stay away from
open areas and isolated high objects such as trees. When indoors,
stay away from windows and doors and avoid using wired electronic
devices. Do not take a shower or bath. Try to unplug unnecessary
appliances before the storm approaches.

&&

LAT...LON 3488 8335 3490 8324 3473 8315 3472 8335
TIME...MOT...LOC 1955Z 348DEG 10KT 3484 8328

CAC

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
432 PM EDT Fri Jul 23 2021

GAZ010-SCZ001-232100-
Rabun GA-Oconee Mountains SC-
432 PM EDT Fri Jul 23 2021

...A STRONG THUNDERSTORM WITH INTENSE LIGHTNING WILL IMPACT SOUTH
CENTRAL RABUN AND WEST CENTRAL OCONEE COUNTIES UNTIL 500 PM EDT...

At 431 PM EDT, Doppler radar was tracking a strong thunderstorm with
intense lightning 5 miles southeast of Clayton. This storm was nearly
stationary.

Locations to be impacted include...
Clayton, Tallulah Gorge State Park, Tallulah Falls, Lakemont and Long
Creek.

In addition to intense lightning, wind gusts up to 40 mph and half
inch hail will be possible in these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Gusty winds can blow down trees that are dead, or that have weakened
root systems. Outdoor furniture and similar items can be tossed
around if not anchored. Seek shelter indoors.

Frequent lightning is occurring with this storm. If outdoors, try to
get indoors or into a hard topped vehicle. Otherwise, stay away from
open areas and isolated high objects such as trees. When indoors,
stay away from windows and doors and avoid using wired electronic
devices. Do not take a shower or bath. Try to unplug unnecessary
appliances before the storm approaches.

&&

LAT...LON 3488 8340 3489 8325 3473 8315 3471 8335
      3472 8336 3473 8338 3473 8341
TIME...MOT...LOC 2031Z 354DEG 4KT 3482 8332

CAC

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
437 PM EDT Fri Jul 23 2021

NCZ052-232115-
Haywood NC-
437 PM EDT Fri Jul 23 2021

...A STRONG THUNDERSTORM WITH INTENSE LIGHTNING WILL IMPACT CENTRAL
HAYWOOD COUNTY UNTIL 515 PM EDT...

At 437 PM EDT, Doppler radar was tracking a strong thunderstorm with
intense lightning 5 miles northeast of Waynesville, or near Lake
Junaluska. This storm was nearly stationary.

Locations to be impacted include...
Waynesville, Lake Junaluska and Clyde.

In addition to intense lightning, wind gusts up to 40 mph and half
inch hail will be possible in these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Gusty winds can blow down trees that are dead, or that have weakened
root systems. Outdoor furniture and similar items can be tossed
around if not anchored. Seek shelter indoors.

Frequent lightning is occurring with this storm. If outdoors, try to
get indoors or into a hard topped vehicle. Otherwise, stay away from
open areas and isolated high objects such as trees. When indoors,
stay away from windows and doors and avoid using wired electronic
devices. Do not take a shower or bath. Try to unplug unnecessary
appliances before the storm approaches.

&&

LAT...LON 3558 8299 3558 8291 3549 8287 3549 8301
TIME...MOT...LOC 2037Z 001DEG 3KT 3555 8295

CAC

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
503 PM EDT Fri Jul 23 2021

GAZ017-018-SCZ001-232130-
Stephens GA-Habersham GA-Oconee Mountains SC-
503 PM EDT Fri Jul 23 2021

...A STRONG THUNDERSTORM WITH INTENSE LIGHTNING WILL IMPACT
NORTHWESTERN STEPHENS...EAST CENTRAL HABERSHAM AND WEST CENTRAL
OCONEE COUNTIES UNTIL 530 PM EDT...

At 503 PM EDT, Doppler radar was tracking a strong thunderstorm with
intense lightning 8 miles north of Toccoa, or near Tallulah Gorge
State Park, moving south at 10 mph.

Locations to be impacted include...
Toccoa, Tallulah Falls, Tallulah Gorge State Park and Long Creek.

In addition to intense lightning, wind gusts up to 40 mph and half
inch hail will be possible in these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Gusty winds can blow down trees that are dead, or that have weakened
root systems. Outdoor furniture and similar items can be tossed
around if not anchored. Seek shelter indoors.

Frequent lightning is occurring with this storm. If outdoors, try to
get indoors or into a hard topped vehicle. Otherwise, stay away from
open areas and isolated high objects such as trees. When indoors,
stay away from windows and doors and avoid using wired electronic
devices. Do not take a shower or bath. Try to unplug unnecessary
appliances before the storm approaches.

&&

LAT...LON 3474 8339 3473 8338 3472 8335 3474 8335
      3475 8333 3477 8332 3477 8326 3460 8320
      3460 8342
TIME...MOT...LOC 2103Z 003DEG 11KT 3470 8332

CAC

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
520 PM EDT Fri Jul 23 2021

SCZ002-232145-
Pickens Mountains SC-
520 PM EDT Fri Jul 23 2021

...A STRONG THUNDERSTORM WITH INTENSE LIGHTNING WILL IMPACT
NORTHWESTERN PICKENS COUNTY UNTIL 545 PM EDT...

At 520 PM EDT, Doppler radar was tracking a strong thunderstorm with
intense lightning 9 miles northwest of Pickens, or near Jocassee
Gorges, moving southeast at 10 mph.

Locations to be impacted include...
Jocassee Gorges, Keowee Toxaway State Park, Lake Keowee, Sunset and
Nine Times.

In addition to intense lightning, wind gusts up to 40 mph and half
inch hail will be possible in these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Gusty winds can blow down trees that are dead, or that have weakened
root systems. Outdoor furniture and similar items can be tossed
around if not anchored. Seek shelter indoors.

Frequent lightning is occurring with this storm. If outdoors, try to
get indoors or into a hard topped vehicle. Otherwise, stay away from
open areas and isolated high objects such as trees. When indoors,
stay away from windows and doors and avoid using wired electronic
devices. Do not take a shower or bath. Try to unplug unnecessary
appliances before the storm approaches.

&&

LAT...LON 3501 8291 3501 8279 3489 8274 3487 8277
      3487 8290 3490 8291 3490 8290 3491 8290
      3492 8291 3494 8290 3494 8291
TIME...MOT...LOC 2120Z 334DEG 9KT 3497 8284

CAC