Severe Thunderstorm Warning 231, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
149 PM EDT Tue Jul 21 2020

.SYNOPSIS...
Ridging aloft will largely remain intact through early next week,
providing hot and humid conditions with heat concerns. Scattered
afternoon to evening thunderstorms are expected through at least
Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
130 PM Update...Convection is underway across the srn NC mtns and it
will take a bit for them to expand east as mlvl clouds have just
recently dissipated elsewhere. Additional convec initiation will
begin south across NE GA and the srn Upstate. These storms will
become quite stg to svr over the next few hrs as moderate sfc-based
instability is in place and dCAPE values are ranging btw 800-1000
J/kg. Damaging straight-line winds will be the main threat over the
next few hrs with isol hydro issues possible later this afternoon.

Morning Update...Morning RAOBs show layers of elevated mixing and
ACU has been developing and reforming across a good portion of the
FA. This has created sfc differential heating and made for a tricky
update. Have adj/d hr/ly temps down across many locales and
interpolated thru 18z. This reduces the HI curve across most areas,
but still expect good heating by mid afternoon to catch-up to the
max temp fcst which has been brought down by a degree or so. The
mid-level clouds may also curtail early afternoon convec initiation
over the nrn NC mtns and NC fthills.

As of 645 AM EDT Tuesday: Main update for the 12Z TAF issuance along
with minor adjustments to temperatures/sky cover to coincide with
latest trends as the rest of the near term forecast remains on
track. A Heat Advisory remains in effect for portions of the FA from
noon to 8 PM EDT today. Overall quiet conditions prevail across the
area this morning with high clouds over the mountains along with
areas of low stratus and fog. Expect fog to linger just after
daybreak. Current temps are in the lower 70s.

Otherwise, with upper ridge still holding strong and dominating the
weather pattern over the Southeast, a stationary front will remain
just north of the area through the forecast period. As a result,
expect another day with hot and humid conditions and diurnally
driven showers and thunderstorms. Instability, plenty of available
moisture, and weak lee troughing along with lingering outflow
boundaries from recent convection will be in place today, as CAMs
continue to depict activity initiating across the mountains, with
pretty good agreement of an east-southeastward propagation into the
NW Piedmont and Upstate SC later this afternoon/early evening. The
primary threat in any stronger/isolated severe storms will be
gusty/damaging winds. Locally heavy rainfall/isolated minor flooding
could not be entirely ruled out. Do expect showers and storms to
taper off later this evening with the loss of daytime heating,
though a few showers/isolated storms could linger into early tonight
along outflow boundaries. Once again, patchy fog will be possible
overnight into Wednesday morning, especially across the mountain
valleys, while elsewhere, conditions are expected to remain quiet.

Starting to feel like a broken record at this point, but once again,
max temps will soar above normal today with areas outside of the
mountains climbing into the mid 90s. These values combined with
dewpoints in the low 70s will allow for heat indices to climb into
the lower 100s, nearing 105 mainly along and east of the I-77
corridor and also into York and Chester counties in SC. Thus, a Heat
Advisory remains in effect for these areas from noon today through 8
PM EDT tonight. Min temperatures will remain above normal into
Wednesday morning.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 335 AM Tuesday: Flat ridging will remain atop the region in
Wednesday into Thursday. Low to mid level convergence and lift
associated with a weak disturbance over the Ohio Valley Wednesday
will be activated and pressed into the area Thursday in response to
zonal flow veering to the northwest. Convection focused across the
mountains Wednesday will become more widespread east of the
mountains Thursday thanks to the increased forcing. Southerly low
level flow, possibly emanating from a tropical disturbance passing
well to the south, may provide a secondary source for convection
possibly lasting into the Thursday night south of I-85. Strong dCAPE
values and modeled updrafts support at least isolated damaging wind
potential with stronger thunderstorms Wednesday. Slow storm movement
and increasing moisture will support a low end threat for flooding,
especially Thursday. Although some cooling is expected mostly due to
the extra cloud cover, it will still feel hot by the afternoon with
heat index values nearing 100 east of the mountains each day.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 345 AM Tuesday: The upper level pattern will continue to
amplify this weekend with little change into next week as we become
sandwiched between a formidable ridge to our west and a trough to
our east. The EURO has continued the trend of dragging a weak upper
low southwest from near the Tidewater region and possibly over the
area this weekend. Either way, guidance continued to agree that a
weak boundary will settle into the area by Saturday, although only
minor cooling/drying is anticipated with this feature. Any relative
lull in diurnal convection this weekend some drying aloft and weak
capping will be short lived as the airmass is quickly modified by
northwest flow atop the region. This pattern can be favorable for
the transport of organized convection originating from the Ohio
River Valley. Temperatures may briefly fall back to near Friday or
Saturday before rebounding by early next week.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
At KCLT and Elsewhere: Another afternoon of flight restrictions and
gusty conds due to tstms traversing the region. Expect TEMPO -TSRA
conds all sites except at KHKY where VCTS should hold. Weak flow
overnight and rad cooling will lower VSBY, likely into the LIFR
range at KAVL and IFR at KHKY. Low StCu is also likely at these
airports. Expect convection Wed afternoon again and have a PROB30
with restrictions at KCLT aft 19z.

Outlook: Diurnal showers and thunderstorms are expected each day
through the extended fcst period. MVFR/IFR restrictions will be
possible each day in any thunderstorms and morning fog development,
especially in the mountain valleys. Otherwise, expect VFR conditions.

Confidence Table...

            17-23Z        23-05Z        05-11Z        11-12Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     Med   66%     Med   66%
KHKY       High 100%     High 100%     High 100%     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...Heat Advisory until 8 PM EDT this evening for NCZ036-037-057-
     071-072-082.
SC...Heat Advisory until 8 PM EDT this evening for SCZ009-014.

&&

SYNOPSIS...65
NEAR TERM...SBK/12
SHORT TERM...65
LONG TERM...65
AVIATION...SBK

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
1059 AM EDT Tue Jul 21 2020

GAZ010-017-018-026-028-029-NCZ033-035-048>053-056-058-059-062>065-
068>070-501>510-SCZ001>008-010>013-019-221500-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Avery-Alexander-
Madison-Yancey-Mitchell-Swain-Haywood-Buncombe-Catawba-Graham-
Northern Jackson-Macon-Southern Jackson-Transylvania-Henderson-
Cleveland-Lincoln-Gaston-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-Anderson-Abbeville-Laurens-Union SC-Greenwood-
1059 AM EDT Tue Jul 21 2020

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 are expected this afternoon and
evening. Some storms will be severe with damaging wind the main
threat. Slow moving or training of storms may also cause isolated
flooding.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Hazardous weather is not 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.

NCZ036-037-057-071-072-082-SCZ009-014-221500-
Iredell-Davie-Rowan-Mecklenburg-Cabarrus-Union NC-York-Chester-
1059 AM EDT Tue Jul 21 2020

...HEAT ADVISORY IN EFFECT UNTIL 8 PM EDT THIS EVENING...

This Hazardous Weather Outlook is for piedmont North Carolina and
upstate South Carolina.

.DAY ONE...Today and tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Heat Advisory.

Scattered showers and thunderstorms are expected this afternoon and
evening. Some storms will be severe with damaging wind the main
threat. Slow moving or training of storms may also cause isolated
flooding.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Hot and humid conditions will continue at least into Wednesday with
afternoon heat index values of 100 to 105 possible.

.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.

Krentz

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
104 PM EDT Tue Jul 21 2020

NCZ052-211730-
Haywood NC-
104 PM EDT Tue Jul 21 2020

...A STRONG THUNDERSTORM WITH INTENSE LIGHTNING WILL IMPACT
NORTHWESTERN HAYWOOD COUNTY UNTIL 130 PM EDT...

At 104 PM EDT, Doppler radar was tracking a strong thunderstorm with
intense lightning 12 miles northwest of Waynesville, or near Smoky
Mountains-Cataloochee. This storm was nearly stationary.

Locations to be impacted include...
Waynesville, Maggie Valley, Smoky Mountains-Cataloochee, Lake
Junaluska, Smoky Mountains-Balsam Mountain, Smoky Mountains-Big
Creek, Cove Creek and Fines Creek.

In addition to intense lightning, wind gusts up to 50 mph and pea
size 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 3573 8292 3547 8300 3554 8316 3556 8316
      3558 8317 3560 8319 3561 8318 3563 8318
      3564 8320 3567 8318 3567 8319 3574 8317
TIME...MOT...LOC 1704Z 285DEG 3KT 3564 8312

RWH

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
121 PM EDT Tue Jul 21 2020

NCZ052-063-064-211745-
Transylvania NC-Haywood NC-Southern Jackson NC-
121 PM EDT Tue Jul 21 2020

...A STRONG THUNDERSTORM WITH INTENSE LIGHTNING WILL IMPACT CENTRAL
TRANSYLVANIA...EAST CENTRAL JACKSON AND SOUTHEASTERN HAYWOOD COUNTIES
UNTIL 145 PM EDT...

At 121 PM EDT, Doppler radar was tracking a strong thunderstorm with
intense lightning 9 miles west of Brevard, or 4 miles south of Black
Balsam Area. This storm was nearly stationary.

Locations to be impacted include...
Brevard, Rosman, Graveyard Fields, Looking Glass, Black Balsam Area,
B.R. Parkway-Black Balsam To Mount Pisgah, B.R. Parkway-Balsam Gap To
Black Balsam Area, Balsam Grove, Wolf Mountain and Connestee.

In addition to intense lightning, wind gusts up to 50 mph and pea
size 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 3528 8297 3529 8292 3530 8293 3531 8295
      3532 8296 3537 8294 3536 8269 3510 8278
      3519 8300
TIME...MOT...LOC 1721Z 285DEG 3KT 3527 8289

RWH

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
214 PM EDT Tue Jul 21 2020

NCZ064-065-SCZ003-211845-
Transylvania NC-Henderson NC-Greenville Mountains SC-
214 PM EDT Tue Jul 21 2020

...A STRONG THUNDERSTORM WILL IMPACT SOUTHEASTERN TRANSYLVANIA...
SOUTH CENTRAL HENDERSON AND NORTHWESTERN GREENVILLE COUNTIES UNTIL
245 PM EDT...

At 214 PM EDT, Doppler radar was tracking a strong thunderstorm 4
miles southeast of Brevard, or near Dupont State Forest, moving east
at 5 mph.

Locations to be impacted include...
Brevard, Etowah, Rosman, Pleasant Ridge State Park, Jones Gap State
Park, Dupont State Forest, Caesars Head State Park, Penrose,
Connestee and Crab Creek.

Wind gusts up to 40 mph, pea size hail and very heavy rainfall rates
up to 2 inches per hour will be possible in these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm 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 3508 8247 3506 8257 3507 8257 3507 8259
      3506 8259 3507 8260 3506 8264 3506 8270
      3505 8275 3507 8277 3507 8278 3508 8278
      3508 8281 3523 8284 3534 8254
TIME...MOT...LOC 1814Z 266DEG 6KT 3521 8266

MOORE

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