Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
748 PM EDT Mon Jun 21 2021

.SYNOPSIS...
A cold front will bring widespread showers and storms to the region
on Tuesday, before continental high pressure builds in on Wednesday,
causing a drop in temperatures and a lull in active weather.  Over
the weekend, renewed moisture should spur a cycle of diurnal showers
and thunderstorms in advance of a slowly-approaching cold front late
in the forecast period.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 6pm EDT Monday: Some strong thunderstorms have erupted over
the piedmont, with more shallow scattered convection over the
mountains.  These showers will continue to move northeastward for
the next several hours at least.

A cold front aided by an anomalous ulvl h5 trof will reach the wrn
NC mtns overnight before sunrise and a few associated tstms may
become quite strong due to enhanced lift and a decent measure of
elCAPE. As the front pushes east thru the day, instability will
remain on the low to moderate side as soundings show deep saturation
and skinny sbCAPE ahead of the line. Nonetheless, bulk shear values
will reach the 30-40 kt range and multicells producing stg outflows
and hail will be likely along and ahead of the front. A few of these
storms could reach severe limits, esp across the NC/SC Piedmont
later in the afternoon during max heating. With the high PWATS ahead
of the boundary, these storms could also produce very good rainfall
rates and localized flooding is possible. The latest NAM lingers the
front over the area thru the evening which is a little
disconcerting, yet most models keep the activity pushing east of the
FA by 00z or so. Max temps Tue will be held about 10 degrees below
normal due to enhance cloud cover and precip.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 145 PM EDT Monday: A 500mb trough axis edges to our east and
lifts out over New England on Wednesday, meaning we'll see minimal
forcing as the height gradient relaxes and winds aloft become nearly
zonal by Thursday.  The frontal boundary settles to our south and
east through Tuesday night, stalling over Georgia and the Atlantic
coast.  Low-end midlevel RHs suggest that precip should be light to
nonexistent by the start of the short-term forecast period for all
but the eastern tier of the CWA.  Can't rule out some patchy rain in
some spots owing to residual low-level moisture, but it should be
low-end as guidance indicates accumulations of less than a quarter
inch past 00Z Wednesday.  This is especially possible in the
mountains, where models may be failing to resolve some low-level
moisture trapped in mountain valleys (in fact, a few models like the
NAMnest and SREF are picking up on this).

In any case, surface flow should veer from northerly to easterly
over the course of the forecast period, acting to introduce a bit of
extra moisture into the profiles on Thursday.  This indicates that
Thursday could see a few more clouds than Wednesday, and perhaps
even an isolated thunderstorm or two.  By and large though,
instability will remain too weak, and profiles too capped, to get
much convective activity going through the afternoon.  Models
continue to trend toward the good moisture remaining well south of
us, so the likelihood of any major impacts on Thursday seems
diminished.

Temps behind the cold front should drop several degrees owing to
strong CAA as the front passes.  So, highs should be a couple
degrees below normal both Wednesday and Thursday.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 200 PM EDT Monday: By Thursday night, the surface high will be
sliding off the Atlantic coast, and surface flow will continue to
veer toward a southeasterly WAA regime.  Atlantic moisture will
creep into the Carolinas and introduce an increase in PoPs starting
on Friday.  Consequently, each day this weekend should feature
partly cloudy to mostly cloudy skies, with a potential for pulse
thunderstorms every afternoon.  By Monday, a slowly-propagating
500mb trough over the Midwest begins to impact the region, as
another frontal boundary pushes across the Appalachians.

Temperature advection will remain weak or nonexistent through to the
weekend, when flow off the Atlantic may prompt minimal WAA. However,
the increased cloud cover at this point should counteract any
temperature increase, so highs should remain a few degrees below
normal for the duration of the period.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: Weather for the next 24 hours will be related
to passage of a cold front currently northwest of the Southern
Appalachians.  A few areas of isolated prefrontal thunder showers
are already passing through the piedmont and mountains this evening,
with another period of showers and thunderstorms occurring overnight
and during the day on Tuesday.  Convection will end as front exits
the region near the 00Z end of the TAF period.  Clouds increase
tonight due to southwesterly moist advection ahead of the front with
CIGS down to IFR levels by early Tuesday morning.  Winds of
generally 10 to 15 kts are initially southwesterly ahead of the
front, becoming northwesterly to northerly behind it. Some fog may
develop in mountain valleys overnight, but winds are expected to be
strong enough to preclude it elsewhere.

Outlook: Drier weather and mostly VFR conds return to the region for
Wed and Thu. A weak warm front affects the region Fri and Sat, which
will likely bring back flight restrictions.

Confidence Table...

            23-05Z        05-11Z        11-17Z        17-18Z
KCLT       High 100%     High 100%     High  91%     High  85%
KGSP       High 100%     High 100%     High  95%     High  85%
KAVL       High 100%     High 100%     High  91%     High  90%
KHKY       High 100%     High 100%     Med   77%     Med   65%
KGMU       High 100%     High 100%     High 100%     Med   75%
KAND       High 100%     High 100%     Med   77%     Med   75%

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...SBK/WJM
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...WJM

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
514 AM EDT Mon Jun 21 2021

GAZ010-017-NCZ033-048>053-058-059-062>065-501-503-505-507-509-
SCZ001>003-220915-
Rabun-Habersham-Avery-Madison-Yancey-Mitchell-Swain-Haywood-Buncombe-
Graham-Northern Jackson-Macon-Southern Jackson-Transylvania-
Henderson-Caldwell Mountains-Burke Mountains-McDowell Mountains-
Rutherford Mountains-Polk Mountains-Oconee Mountains-
Pickens Mountains-Greenville Mountains-
514 AM EDT Mon Jun 21 2021

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

.DAY ONE...Today and tonight.

Scattered showers and thunderstorms are expected to develop across
the mountains of the Carolinas and northeast Georgia this afternoon.
Storms will become more numerous tonight, as a cold front pushes in
from the west. A few storms may become severe, with damaging wind
gusts the main threat. Also, isolated flash flooding cannot be ruled
out.

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

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed. Please relay any information about
observed severe weather to the NWS while following all local, state,
and CDC guidelines.

GAZ018-026-028-029-NCZ035>037-056-057-068>072-082-502-504-506-508-
510-SCZ004>014-019-220915-
Stephens-Franklin-Hart-Elbert-Alexander-Iredell-Davie-Catawba-Rowan-
Cleveland-Lincoln-Gaston-Mecklenburg-Cabarrus-Union NC-
Greater Caldwell-Greater Burke-Eastern McDowell-Greater Rutherford-
Eastern Polk-Greater Oconee-Greater Pickens-Greater Greenville-
Spartanburg-Cherokee-York-Anderson-Abbeville-Laurens-Union SC-
Chester-Greenwood-
514 AM EDT Mon Jun 21 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 showers and thunderstorms may push east from the mountains
into the Piedmont this evening through the overnight tonight. The
main threat will be cloud-to-ground lightning, gusty winds, and
locally heavy rainfall.

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

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

ARK

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
604 PM EDT Mon Jun 21 2021

SCZ006>009-013-212245-
York SC-Cherokee SC-Union SC-Spartanburg SC-Greater Greenville SC-
604 PM EDT Mon Jun 21 2021

...THUNDERSTORMS WITH TORRENTIAL RAINFALL WILL IMPACT EAST CENTRAL
GREENVILLE...SOUTHWESTERN YORK...CENTRAL SPARTANBURG...SOUTHERN
CHEROKEE AND NORTHERN UNION COUNTIES UNTIL 645 PM EDT...

At 604 PM EDT, Doppler radar indicated thunderstorms with torrential
rainfall along a line extending from 11 miles east of Downtown
Greenville to 9 miles south of Spartanburg to near Union, and moving
northeast at 25 mph.

Locations to be impacted include...
Spartanburg, Five Forks, Pacolet, Roebuck, Jonesville, Pacolet Mills,
Reidville, Croft State Park, Moore and Cedar Springs.

Wind gusts up to 45 mph, dime size hail and very heavy rainfall rates
up to 2 inches per hour will be possible in these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

The combination of gusty winds and saturated soil conditions will
cause scattered trees and power lines to fall. Seek shelter inside an
interior room.

Dime to nickel size hail can cause considerable damage to vehicles.
Consider moving vehicles to a covered storage area before the storm
arrives.

These storms may intensify, so be certain to monitor local radio and
tv stations, as well as local cable tv outlets for additional
information and possible warnings from the National Weather Service.

&&

LAT...LON 3478 8200 3477 8213 3478 8215 3477 8215
      3476 8234 3496 8192 3497 8158 3489 8129
      3472 8170
TIME...MOT...LOC 2204Z 244DEG 21KT 3480 8220 3481 8193 3477 8172

8

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
608 PM EDT Mon Jun 21 2021

SCZ006-012-212245-
Laurens SC-Greater Greenville SC-
608 PM EDT Mon Jun 21 2021

...A STRONG THUNDERSTORM WITH INTENSE LIGHTNING WILL IMPACT
NORTHWESTERN LAURENS AND SOUTHEASTERN GREENVILLE COUNTIES UNTIL 645
PM EDT...

At 608 PM EDT, Doppler radar was tracking a strong thunderstorm with
intense lightning 12 miles south of Downtown Greenville, or 5 miles
south of Donaldson Center, moving east at 25 mph.

Locations to be impacted include...
Simpsonville, Fountain Inn, Piedmont and Fork Shoals.

In addition to intense lightning, wind gusts up to 45 mph and dime
size hail will be possible in these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

The combination of gusty winds and saturated soil conditions will
cause scattered trees and power lines to fall. Seek shelter inside an
interior room.

Dime to nickel size hail can cause considerable damage to vehicles.
Consider moving vehicles to a covered storage area before the storm
arrives.

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 3462 8245 3464 8245 3465 8246 3466 8246
      3467 8247 3468 8246 3469 8246 3478 8219
      3462 8213
TIME...MOT...LOC 2208Z 255DEG 22KT 3467 8238

8

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
700 PM EDT Mon Jun 21 2021

NCZ033-501>504-212345-
Caldwell Mountains NC-Burke Mountains NC-Greater Burke NC-
Greater Caldwell NC-Avery NC-
700 PM EDT Mon Jun 21 2021

...STRONG THUNDERSTORMS WILL IMPACT CALDWELL...SOUTHEASTERN AVERY AND
NORTHWESTERN BURKE COUNTIES UNTIL 745 PM EDT...

At 700 PM EDT, Doppler radar indicated strong thunderstorms along a
line extending from 3 miles southeast of Blowing Rock to 10 miles
east of Spruce Pine, and moving east at 15 mph.

Locations to be impacted include...
Lenoir, Gamewell, Blowing Rock In Caldwell County, Table Rock,
Edgemont, Globe, Collettsville, Patterson and Upton.

Wind gusts up to 45 mph and pea size hail will be possible in these
areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

The combination of gusty winds and saturated soil conditions will
cause scattered trees and power lines to fall. Seek shelter inside an
interior room.

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.

These storms may intensify, so be certain to monitor local radio and
tv stations, as well as local cable tv outlets for additional
information and possible warnings from the National Weather Service.

&&

LAT...LON 3612 8155 3610 8152 3610 8150 3609 8147
      3609 8145 3607 8144 3607 8141 3605 8139
      3604 8140 3604 8137 3582 8163 3585 8192
      3588 8191 3591 8191 3612 8170
TIME...MOT...LOC 2300Z 271DEG 14KT 3610 8163 3590 8188

8

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
808 PM EDT Mon Jun 21 2021

NCZ051-052-058-059-062-063-220100-
Haywood NC-Graham NC-Swain NC-Southern Jackson NC-
Northern Jackson NC-Macon NC-
808 PM EDT Mon Jun 21 2021

...A CLUSTER OF THUNDERSTORMS WILL IMPACT MACON...NORTHWESTERN
JACKSON...SWAIN...SOUTHEASTERN GRAHAM AND CENTRAL HAYWOOD COUNTIES
UNTIL 900 PM EDT...

At 808 PM EDT, Doppler radar indicated the leading edge of a cluster
of thunderstorms along a line extending from 6 miles southeast of
Gatlinburg to 5 miles south of Andrews, and moving east at 30 mph.

Locations to be impacted include...
Franklin, Sylva, Waynesville, Bryson City, Cherokee, Cullowhee, Lake
Junaluska, Maggie Valley, Balsam and Webster.

Wind gusts up to 40 mph and very heavy rainfall rates up to 2 inches
per hour 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.

These storms may intensify, so be certain to monitor local radio and
tv stations, as well as local cable tv outlets for additional
information and possible warnings from the National Weather Service.

&&

LAT...LON 3561 8345 3562 8340 3567 8334 3566 8330
      3571 8325 3570 8290 3564 8287 3500 8332
      3502 8353 3511 8362 3513 8362 3514 8365
      3515 8365 3515 8374 3519 8371 3520 8373
      3523 8369 3526 8371 3524 8375
TIME...MOT...LOC 0008Z 271DEG 28KT 3567 8340 3513 8380

8

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
852 PM EDT Mon Jun 21 2021

NCZ048-049-053-220130-
Buncombe NC-Yancey NC-Madison NC-
852 PM EDT Mon Jun 21 2021

...A STRONG THUNDERSTORM WILL IMPACT MADISON...NORTH CENTRAL BUNCOMBE
AND NORTHWESTERN YANCEY COUNTIES UNTIL 930 PM EDT...

At 852 PM EDT, Doppler radar was tracking a strong thunderstorm 10
miles northwest of Marshall, or near Hot Springs, moving east at 30
mph.

Locations to be impacted include...
Marshall, Mars Hill, Hot Springs, Faust, Allenstand, Walnut, Wolf
Ridge, Barnardsville, Spring Creek and Swiss.

Wind gusts up to 45 mph and very heavy rainfall rates up to 2 inches
per hour will be possible in these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

The combination of gusty winds and saturated soil conditions will
cause scattered trees and power lines to fall. Seek shelter inside an
interior room.

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 3600 8237 3571 8239 3575 8293 3587 8292
      3588 8290 3591 8291 3594 8290 3595 8285
      3592 8282 3597 8278 3598 8279 3599 8278
      3600 8261 3599 8260 3597 8261 3595 8256
      3600 8248
TIME...MOT...LOC 0052Z 270DEG 27KT 3587 8285

8

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
900 PM EDT Mon Jun 21 2021

NCZ035-036-220145-
Iredell NC-Alexander NC-
900 PM EDT Mon Jun 21 2021

...A STRONG THUNDERSTORM WITH INTENSE LIGHTNING WILL IMPACT
NORTHEASTERN ALEXANDER AND NORTH CENTRAL IREDELL COUNTIES UNTIL 945
PM EDT...

At 900 PM EDT, Doppler radar was tracking a strong thunderstorm with
intense lightning 9 miles southeast of Wilkesboro, or 6 miles
northwest of Love Valley, moving east at 20 mph.

Locations to be impacted include...
Love Valley, Vashti and Union Grove.

In addition to intense lightning, wind gusts up to 40 mph 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 3605 8074 3602 8074 3597 8115 3603 8116
      3604 8113 3603 8107 3606 8098 3606 8089
TIME...MOT...LOC 0100Z 260DEG 19KT 3603 8108

8