Severe Thunderstorm Warning 107, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
245 PM EDT Fri May 22 2020

.SYNOPSIS...
A strengthening high pressure ridge will build over the Southeast
through the weekend, with warming temperatures but also afternoon
and evening thunderstorms redeveloping each day through at least
Tuesday.

&&

.NEAR TERM /THROUGH SATURDAY/...
Ongoing convec is remaining mostly sub-severe with a couple bowing
echoes producing strong to possibly severe-level winds. The atmos
ahead of the line is modestly unstable and with good ulvl support
and expect these storms to remain semi-organized as it moves east
thru the afternoon. The best shot of deeper and large hail producing
cells will be across the srn zones where sbCAPE has climbed into the
1500 J/kg range south of a instability gradient. A couple weak
tornadoes are possible...mainly due to potential line breaks as hodos
are not overly impressive and sfc winds remain fairly weak and
un-backed within a weak llvl ridge axis.

A line of trailing showers will align along a bndry over the Upstate
overnight and a few-short lived tstms are possible, but mainly
expect light to moderate rain showers thru daybreak. isolated to
scattered afternoon showers and thunderstorms will return
Sat...however not expecting good organization, yet a couple stg/svr
storms may break the cap before a pronounced ulvl ridge axis
develops loft. Min temps will remain abt 10 degrees abv
normal...while high temps Sat reach arnd 5 degrees abv normal.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 1230 PM Fri: Just ahead of an upper ridge, a warm front should
remain northeast of the CWA Saturday night. Guidance depicts some
nocturnal convection firing over the middle Ohio River Valley,
possibly as nearby as upper East TN and SW VA, as a weak vort max
rounds the ridge axis. Thinking is that any resulting MCS likely
would miss our area to the N, but we will carry a small PoP overnight
into Sunday morning. Beyond that, and assuming such a system does not
work us over early in the day, Sunday afternoon will be seasonably
warm and moist under the ridge. We won't have much of a triggering
mechanism, and shear will be weak, so pulse storms or loosely
organized clusters appear likely to fire over the Blue Ridge and
drift into the Piedmont.

Some guidance continues to suggest a cooler, wedge-like airmass
originating in the Canadian Maritimes will be shunted into VA/NC
sometime Sunday or Sunday night, by the offshore sfc low. This does
not look any more likely than it did on yesterday's guidance, giving
us more confidence on a rather warm Sunday, with highs in the upper
80s across much of the Piedmont. This pattern however does look to
introduce cloud cover and maintain easterly to southeasterly flow
overnight into Monday, suggesting cooler temps and reduced convective
potential in the Piedmont Monday afternoon. However, the mountains
and Escarpment should see similar chances compared to Sunday. Lapse
rates will remain fairly strong above whatever capping the cloud
cover were to produce, so the storms that do fire still could become
strong to severe, with damaging winds and hail the most likely mode
of any severe wx.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 200 PM Fri: The Deep East Coast ridge in place at the start of
the period will develop into an anticyclone by Wednesday as cutoff
lows form over the southern Plains and near Bermuda. The resulting
omega block will keep our early week pattern in place for the rest of
the medium range. The continued moist southeasterly flow suggests
somewhat unsettled conditions will continue, with above-average cloud
cover and precip chances. Temps look to end up near normal given the
strength of the ridge being offset by the cloud cover. Diurnal
instability will develop each day mainly over the mountains and
Savannah River Valley, with slightly favorable upper level lapse
rates throughout the area, but some degree of capping over the
eastern and southern CWA keeping chances lower there. Weak shear
within the ridge but relatively high diurnal CAPE implies pulse
storms will continue to be the dominant form of convection Tuesday.
Wednesday and Thursday, lapse rates are weaker aloft and CAPE values
are accordingly lower, which may keep thunderstorms totally at bay.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
At KCLT and Elsewhere: A mixed bag in the TAFs with a line of convec
storms moving quickly across the FA this afternoon. Have timings for
TS and VCTS with some lowering CIGs into MVFR mainly across the the
mtns this afternoon and then again across the non/mtns late within
PROB30s for general thunder and precip trailing the main MCS this
afternoon/evening. Winds will remain fairly low-end outside of gusty
storms as a llvl ridge builds in from the east.

Outlook: Afternoon to evening showers and thunderstorms will be
possible over the weekend and into early next week. Restrictions are
also possible each morning from low clouds and fog and again later
in the day under any thunderstorms.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High  99%     High 100%     High  86%     High  87%
KGSP       High  95%     High 100%     High  98%     High  99%
KAVL       High  90%     High  95%     Med   67%     High  91%
KHKY       High  95%     High  91%     High  83%     High  95%
KGMU       High  90%     High 100%     High 100%     High 100%
KAND       High  97%     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...08
NEAR TERM...SBK
SHORT TERM...08
LONG TERM...08
AVIATION...SBK

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
133 PM EDT Fri May 22 2020

GAZ010-017-018-026-028-029-NCZ036-037-056-057-068>072-082-503>510-
SCZ001>014-019-231745-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Iredell-Davie-Catawba-
Rowan-Cleveland-Lincoln-Gaston-Mecklenburg-Cabarrus-Union NC-
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-
133 PM EDT Fri May 22 2020

...SEVERE THUNDERSTORM WATCH 202 IN EFFECT UNTIL 8 PM EDT THIS
EVENING...

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

.DAY ONE...This afternoon and tonight.

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

   Severe Thunderstorm Watch.

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

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.

NCZ033-035-048>053-058-059-062>065-501-502-231745-
Avery-Alexander-Madison-Yancey-Mitchell-Swain-Haywood-Buncombe-
Graham-Northern Jackson-Macon-Southern Jackson-Transylvania-
Henderson-Caldwell Mountains-Greater Caldwell-
133 PM EDT Fri May 22 2020

This Hazardous Weather Outlook is for piedmont North Carolina and
western North Carolina.

.DAY ONE...This afternoon and tonight.

Thunderstorms are possible afternoon and evening. Cloud to ground
lightning and locally heavy rainfall can be expected with any of
these thunderstorms. The thunderstorms may also produce very gusty
winds, and damaging gusts to 60 mph will be possible in a couple
storms. Flash flooding from torrential rainfall is also possible.

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

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

8

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
107 PM EDT Fri May 22 2020

GAZ010-NCZ062>064-SCZ001-002-004-221745-
Rabun GA-Transylvania NC-Southern Jackson NC-Macon NC-
Pickens Mountains SC-Greater Oconee SC-Oconee Mountains SC-
107 PM EDT Fri May 22 2020

...A STRONG THUNDERSTORM WILL IMPACT RABUN...SOUTHEASTERN MACON...
SOUTHWESTERN TRANSYLVANIA...SOUTHEASTERN JACKSON...NORTHWESTERN
PICKENS AND OCONEE COUNTIES UNTIL 145 PM EDT...

At 106 PM EDT, Doppler radar was tracking a strong thunderstorm 4
miles southwest of Clayton, or near Tiger, moving east at 40 mph.

Locations to be impacted include...
Seneca, Walhalla, Clayton, Highlands, Mountain City, Tiger, Dillard,
Sky Valley, Cashiers and Salem.

Wind gusts up to 50 mph, pea size hail and very heavy rainfall rates
up to 2 inches per hour will be possible in these areas.

Doppler radar indicates weak rotation with this storm. Spin-up of a
very brief, weak tornado cannot be ruled out. Be prepared to take
immediate action if a tornado is sighted or a Tornado Warning is
issued.

LAT...LON 3517 8285 3482 8287 3481 8289 3478 8288
      3474 8290 3474 8288 3468 8288 3471 8335
      3473 8338 3473 8341 3475 8343 3473 8348
      3474 8352 3499 8355 3500 8348 3500 8352
      3502 8352 3504 8356 3506 8356
TIME...MOT...LOC 1706Z 266DEG 33KT 3483 8345

RM

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
134 PM EDT Fri May 22 2020

GAZ018-026-028-SCZ001-004-005-010-221800-
Hart GA-Franklin GA-Stephens GA-Greater Pickens SC-Greater Oconee SC-
Anderson SC-Oconee Mountains SC-
134 PM EDT Fri May 22 2020

...STRONG THUNDERSTORMS WILL IMPACT FRANKLIN...STEPHENS...
NORTHWESTERN HART...NORTHWESTERN ANDERSON...SOUTHWESTERN PICKENS AND
OCONEE COUNTIES UNTIL 200 PM EDT...

At 134 PM EDT, Doppler radar indicated strong thunderstorms along a
line extending from 8 miles west of Walhalla to 5 miles north of
Homer, and moving east at 40 mph.

Locations to be impacted include...
Clemson, Toccoa, Seneca, Walhalla, Carnesville, Hartwell, Central,
Pendleton, Liberty and Westminster.

Wind gusts up to 50 mph, pea size hail and very heavy rainfall rates
up to 2 inches per hour will be possible in these areas.

Doppler radar indicates weak rotation with These storms. Spin-up of a
very brief, weak tornado cannot be ruled out. Be prepared to take
immediate action if a tornado is sighted or a Tornado Warning is
issued.

A Severe Thunderstorm Watch remains in effect until 800 PM EDT for
northeastern Georgia...and Upstate South Carolina.

LAT...LON 3436 8339 3443 8338 3446 8340 3448 8346
      3453 8344 3481 8320 3483 8290 3481 8290
      3483 8284 3485 8262 3432 8297
TIME...MOT...LOC 1734Z 275DEG 35KT 3477 8320 3441 8353

RM

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
200 PM EDT Fri May 22 2020

GAZ018-026-028-029-SCZ001-004>006-010-221845-
Elbert GA-Hart GA-Franklin GA-Stephens GA-Greater Pickens SC-
Greater Oconee SC-Anderson SC-Oconee Mountains SC-
Greater Greenville SC-
200 PM EDT Fri May 22 2020

...STRONG THUNDERSTORMS WILL IMPACT FRANKLIN...STEPHENS...
NORTHWESTERN ELBERT...HART...CENTRAL GREENVILLE...ANDERSON...SOUTHERN
PICKENS AND SOUTHERN OCONEE COUNTIES UNTIL 245 PM EDT...

At 159 PM EDT, Doppler radar indicated strong thunderstorms along a
line extending from 8 miles north of Clemson to 4 miles northwest of
Carnesville, and moving east at 40 mph.

Locations to be impacted include...
Anderson, Easley, Clemson, Seneca, Hartwell, Carnesville, Greenville
Downtown, Toccoa, Greenville Eastside and West Greenville.

Wind gusts up to 50 mph, pea size hail and very heavy rainfall rates
up to 2 inches per hour will be possible in these areas.

Doppler radar indicates weak rotation with These storms. Spin-up of a
very brief, weak tornado cannot be ruled out. Be prepared to take
immediate action if a tornado is sighted or a Tornado Warning is
issued.

A Severe Thunderstorm Watch remains in effect until 800 PM EDT for
northeastern Georgia...and Upstate South Carolina.

LAT...LON 3417 8310 3423 8308 3427 8312 3424 8317
      3424 8325 3426 8330 3423 8335 3426 8334
      3433 8339 3443 8338 3446 8340 3448 8343
      3450 8343 3485 8290 3481 8290 3486 8280
      3485 8229 3421 8274 3416 8276 3415 8306
TIME...MOT...LOC 1759Z 268DEG 34KT 3479 8286 3443 8327

RM