Upslope flow behind a weak cold front helped to trigger a few thunderstorms over western North Carolina during the afternoons of the 20th and 21st. Some of the storms produced small areas of wind damage and large hail.
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS GSP wrote it up.
Upslope flow behind a weak cold front helped to trigger a few thunderstorms over western North Carolina during the afternoons of the 20th and 21st. Some of the storms produced small areas of wind damage and large hail.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Greenville-Spartanburg, SC wrote its last area forecast discussion before the first event at Aug 20, 3:25 PM EST, 1 hour 20 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 425 PM EDT SAT AUG 20 2011 .SYNOPSIS... WEAK HIGH PRESSURE WILL GIVE WAY TO A COLD FRONT THAT WILL APPROACH FROM THE NORTHWEST LATE SUNDAY. THE FRONT IS EXPECTED TO STALL JUST SOUTH OF OUR AREA EARLY IN THE WEEK AND SLOWLY DISSIPATE. MOISTURE WILL INCREASE LATE IN THE WEEK AS WE BECOME MORE CONCERNED OF TROPICAL ACTIVITY. && .NEAR TERM /THROUGH SUNDAY/... 2025 UTC UPDATE...POPS HAVE BEEN RAISED ALONG THE BLUE RIDGE WHERE COVERAGE HAS INCREASED LATE THIS AFTERNOON. PREVIOUS DISCUSSION...BUILDING MID LEVEL HEIGHTS HAS RESULTED IN AN AREA OF NVA ACROSS THE SOUTHERN APPALACHIAN AREA THIS AFTERNOON AND EVENING. OBSERVED SOUNDING AT KFFC INDICATED A SIGNIFICANT INVERSION AROUND H5. THE COMBINATION OF HIGHS IN THE MID 80S ACROSS THE MTNS TO L90S EAST AND DWPTS IN THE MID 60S HAVE RESULTED IN AFTERNOON CAPES BETWEEN 2000 TO 2500 J/KG. GIVEN THE WEAK FORCING AND LINGERING CIN...POPS ACROSS THE MTNS AND FOOTHILLS WILL REMAIN CHC THROUGH EARLY THIS EVENING...I WILL FAVOR SCHC POPS EAST THIS AFTERNOON WITH A SLIGHT INCREASE TO LCHC EARLY THIS EVENING AS MTN ACTIVITY MOVES SLOWLY EAST. BASED ON THE OBSERVED PROFILES AND INSTABILITY...AN ISO SVR EVENT OR AREA OF EXCESSIVE RAINFALL IS A POSSIBILITY. BY MIDNIGHT...EXPECT THE ENVIRONMENT TO LARGELY STABILIZE. HOWEVER...FORECAST SOUNDINGS SHOW ELEVATED INSTABILITY REMAINING THROUGH THE NIGHT. BY THE PRE DAWN HOURS...EXPECTED SHRA ACTIVITY TO END COMPLETELY...LEAVING ONLY DEBRIS CLOUDS AND LIGHT TO CALM WINDS. HOWEVER...FOG MAY DEVELOP LATE TONIGHT NEAR AREAS OF RECENT RAIN AND MTN VALLEYS. LOW TEMPS WILL REMAIN SLIGHTLY ABOVE NORMAL. SUNDAY...A COLD FRONT WILL SWEEP EAST ACROSS KY/TN THROUGH THE DAY...REACHING THE SOUTHERN APPALACHIANS DURING THE LATE AFTERNOON. SOUTH SFC WINDS AHEAD OF THE FRONT WILL STRENGTHEN THROUGH THE DAY...MAINTAINING DEWPOINT VALUES IN THE UPPER 60S TO AROUND 70. HIGH TEMPS WILL WARM INTO THE MID 80S ACROSS THE MTNS TO AROUND 90 EAST. FORECAST SOUNDINGS INDICATE THAT THE MID INVERSION WILL FLATTEN...STEEPENING LAPSE RATES BELOW H6. IN FACT...FORECAST SOUNDINGS SUPPORT CAPES BETWEEN 2000 TO 3000 J/KG. IN ADDITION...LOW TO MID LEVEL WINDS WILL INCREASE TO 20 TO 30 KTS...ESPECIALLY IN THE MID LEVELS. MESOSCALE MODELS INDICATE THAT TSRA WILL DEVELOP ACROSS THE MTNS AROUND MID DAY AND DEVELOP INTO A BAND PARALLEL TO THE FRONT. 4 KM WRF INDICATES THAT THE LINE WILL DEVELOP A HEALTHY COLD POOL AND ACCELERATE EAST ACROSS THE FOOTHILLS AND PIEDMONT DURING THE AFTERNOON. GIVEN THE INSTABILITY AND WINDS...IT APPEARS THAT MULTICELL LINES WILL HAVE THE POTENTIAL FOR SVR WIND AND POSSIBLY SVR HAIL...ESPECIALLY ACROSS THE NC ZONES GIVEN GREATER WIND SPEEDS. I WILL INCREASE POPS TO LIKELY ACROSS THE AREA. WE WILL HIGHLIGHT THE SVR POTENTIAL IN THE HWO. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... AS OF 230 PM SATURDAY...THE MODELS REINFORCE THE UPPER TROF ALONG THE EAST COAST ON SUNDAY NIGHT AS A STRONG UPPER SHORT WAVE ROTATES THROUGH THE EASTERN GREAT LAKES. THIS SHOULD HAVE NO TROUBLE PUSHING A COLD FRONT THROUGH THE FORECAST AREA SUNDAY EVENING. EXPECT A CONTINUATION OF THE CONVECTIVE ACTIVITY THAT WE HAVE AT SUNSET SUNDAY EVENING...MOVING EAST ACROSS THE PIEDMONT WITH THE FRONT. HAVE HELD ONTO A LOW CHANCE POP ON THE TN BORDER FOR LINGERING UPSLOPE SHOWERS AS THE FRONT MOVES THROUGH. THE SHOWERS SHOULD BE TO THE EAST OF THE FORECAST AREA BY AROUND SUNRISE ON MONDAY. THEREAFTER...EXPECT A QUIET START TO THE WORK WEEK. THE WESTERN CAROLINAS SHOULD BE UNDER A DEEP AND DRY NW FLOW ALOFT BOTH MONDAY AND TUESDAY AS THE UPPER TROF AXIS HOLDS ALONG THE E COAST. THAT WILL SUPPORT SURFACE HIGH PRESSURE SETTLING DOWN OVER THE CENTRAL APPALACHIANS AND MID ATLANTIC THROUGH TUESDAY. FOR THE MOST PART...THIS SHOULD DISCOURAGE DEEP CONVECTION. ON MONDAY AFTERNOON...THOUGH...HAVE ALLOWED A SLIGHT CHANCE OVER THE HIGHER TERRAIN OWING TO LINGERING LOW LEVEL MOISTURE. MONDAY NIGHT... TUESDAY...AND TUESDAY NIGHT SHOULD BE PRECIP-FREE. TEMPS WERE NUDGED TOWARD A BLEND OF GUIDANCE IN GENERAL...BUT THE LOWER MET GUIDANCE WAS FAVORED FOR TUESDAY NIGHT. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... AS OF 230 PM SATURDAY...WE WILL BEGIN WITH WHAT SEEMS REASONABLY CERTAIN...AND THAT IS SOME MOISTURE RETURN STARTING EARLY WEDNESDAY AND CONTINUING THROUGH THE END OF THE WEEK. ANOTHER REINFORCING SHORT WAVE IS EXPECTED TO DROP DOWN THROUGH THE MIDWEST AND OH VALLEY TUESDAY NIGHT AND WEDNESDAY WHICH WILL PUSH ANOTHER COLD FRONT INTO THE REGION. WITH THE SURFACE HIGH MOVING OFF THE MID ATLANTIC COAST TUESDAY NIGHT...EXPECT AN INFLUX OF MOISTURE FROM THE ATLANTIC AHEAD OF THE FRONT. SO...SCATTERED THUNDERSTORMS LOOK LIKE A SAFE BET ON WEDNESDAY AFTERNOON AND EVENING...AT LEAST OVER THE MTNS AND FOOTHILLS. THE CONTINUATION OF THE MOIST EASTERLY FLOW SHOWN BY THE MODELS SUGGESTS THAT WE WILL NOT SEE MUCH OF A DIURNAL DROP OFF WEDNESDAY NIGHT...SO THE CHANCE POP WILL RUN RIGHT THROUGH FRIDAY FOR THE MOST PART AS THE FRONT STALLS NEARBY. WHICH BRINGS US TO THE WEEKEND...WHICH IS BY NO MEANS CERTAIN. IT SEEMS REASONABLE TO EXPECT SOME PART OF THE SOUTHEAST TO BE IN SOME DANGER FROM A TROPICAL CYCLONE SHOWN BY THE COLLECTION OF MODEL GUIDANCE IN THE VICINITY OF THE FL PENINSULA ON SATURDAY. GOING WITH THE HPC POSITION OVER THE ERN GULF SATURDAY MORNING...EXPECT EVEN MORE ATLANTIC MOISTURE TO RUN UPSLOPE FROM THE SOUTHEAST AND HAVE SOME FOCUS ALONG THE OLD SURFACE FRONT OVER THE CAROLINAS. SO...HAVE LEANED TOWARD A LOWER DIURNAL RANGE OF TEMPS FOR SATURDAY AND TRENDED TOWARD THE COOLER FIRST CUT OF HPC TEMPS. HAVE ALSO GONE WITH A BLANKET CHANCE OF PRECIP THROUGH THE END OF THE DAY. PEOPLE ACROSS THE CAROLINAS WILL WANT TO KEEP TRACK OF THIS ONE FOR SATURDAY NIGHT AND SUNDAY. && .AVIATION /21Z SATURDAY THROUGH THURSDAY/... AT KCLT...STEADY SOUTHEAST WINDS WILL SLOWLY VEER SOUTH THROUGH TONIGHT...WITH SPEEDS FAVORING 5 KTS. SCT CU SHOULD DEVELOP ACROSS THE TERMINAL BY 19Z AND REMAIN UNTIL SUNSET. SLIGHT RISK OF SHRA/TSRA THIS AFTERNOON AND EARLY EVENING...TOO LOW OF A CHANCE TO MENTION IN THE TAF AT THIS TIME. LIGHT WINDS AND NARROW DEWPOINT DEPRESSIONS MAY SUPPORT LIGHT FOG OR HAZE AROUND DAWN. BEFORE 18Z...INCREASING SOUTH WIND AND CU AFTER SUNRISE. A LINE OF SHRA/TSRA IS EXPECTED TO SWEEP ACROSS THE TERMINAL DURING THE LATE AFTERNOON...BUT BEYOND THE SCOPE OF THE 18Z TAF. ELSEWHERE...SCT SHRA/TSRA WILL CONTINUE TO DEVELOP OVER THE MTNS AND FOOTHILLS THROUGH EARLY EVENING. I WILL CARRY A CB IN THE TAFS DURING THE LATE AFTERNOON THROUGH EARLY EVENING...EXCEPT FOR KAND. STEADY SOUTHEAST WINDS WILL SLOWLY VEER SOUTH THROUGH TONIGHT...WITH SPEEDS FAVORING 5 KTS POSSIBLY BECOMING CALM OVERNIGHT. MOS CONSENSUS ONCE AGAIN INDICATING DENSE FOG FOR KAVL DURING THE PRE DAWN HOURS. HOWEVER...CLOSE DEWPOINT DEPRESSIONS AND A FAIR CHC FOR FRESH RA BY THE END OF THE EVENING MAY SUPPORT FOG OVERNIGHT. FOR KAVL...I WILL VIS DOWN TO 1SM BY 8Z WITH RECOVERY AROUND 14Z. BEFORE 18Z...INCREASING SOUTH WIND AND CU AFTER SUNRISE. A LINE OF SHRA/TSRA IS EXPECTED TO SWEEP ACROSS THE TERMINAL DURING THE LATE AFTERNOON...BUT BEYOND THE SCOPE OF THE 18Z TAF. OUTLOOK...THROUGH EARLY NEXT WEEK...A MORE UNSETTLED WEATHER PATTERN SHOULD RESULT IN CONTINUED DEVELOPMENT OF ISOLATED TO WIDELY SCATTERED DIURNAL CONVECTION EACH AFTN. MORNING FOG WILL ALSO BE POSSIBLE...ESP IN MTN VALLEYS AND WHERE RAIN FALLS THE DAY BEFORE. AN EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLE SHOWING THE PERCENTAGE OF GUIDANCE MEMBERS AGREEING WITH THE SCHEDULED ISSUANCE CATEGORY IS AVAILABLE AT FOLLOWING LINK (USE LOWER CASE)... WWW.WEATHER.GOV/GSP/AVIATION/TABLES.HTM && .GSP WATCHES/WARNINGS/ADVISORIES... GA...NONE. NC...NONE. SC...NONE. && SYNOPSIS...PAT NEAR TERM...JAT/NED SHORT TERM...PM LONG TERM...PM AVIATION...NED
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 256 PM EDT SAT AUG 20 2011 GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065- 068>072-082-501>510-SCZ001>014-019-211900- RABUN-HABERSHAM-STEPHENS-FRANKLIN-HART-ELBERT-AVERY-ALEXANDER- IREDELL-DAVIE-MADISON-YANCEY-MITCHELL-SWAIN-HAYWOOD-BUNCOMBE-CATAWBA- ROWAN-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- 256 PM EDT SAT AUG 20 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHEAST GEORGIA...PIEDMONT NORTH CAROLINA...WESTERN NORTH CAROLINA AND UPSTATE SOUTH CAROLINA. .DAY ONE...THIS AFTERNOON AND TONIGHT. SCATTERED THUNDERSTORMS WILL DEVELOP ACROSS THE WESTERN CAROLINAS AND NORTHEAST GEORGIA THIS AFTERNOON AND EVENING. THE MAIN THREATS WITH THESE THUNDERSTORMS WILL BE CLOUD TO GROUND LIGHTNING AND BRIEFLY HEAVY RAINFALL. AN ISOLATED SEVERE THUNDERSTORM CANNOT BE RULED OUT. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY. A LINE OF THUNDERSTORMS MAY DEVELOP OVER THE MOUNTAINS AND BLUE RIDGE SUNDAY AFTERNOON...AND THEN SHOULD MOVE EAST ACROSS THE FOOTHILLS AND PIEDMONT IN THE AFTERNOON AND EVENING. SOME OF THESE THUNDERSTORMS MAY CONTAIN DAMAGING WIND GUSTS AND LARGE HAIL... ESPECIALLY ACROSS NORTH CAROLINA. .SPOTTER INFORMATION STATEMENT... NONE. MOORE
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
446 PM EDT SAT AUG 20 2011
NCZ503>506-202130-
BURKE MOUNTAINS-EASTERN MCDOWELL-GREATER BURKE-MCDOWELL MOUNTAINS-
446 PM EDT SAT AUG 20 2011
...A STRONG THUNDERSTORM WILL AFFECT NORTHEASTERN MCDOWELL AND
WESTERN BURKE COUNTIES THROUGH 530 PM EDT...
AT 444 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 5 MILES NORTHEAST OF LAKE JAMES...OR 11 MILES
NORTHEAST OF MARION...MOVING SOUTHEAST AT 5 MPH.
THIS STORM WILL BE NEAR...
LAKE JAMES...
DIME SIZE HAIL...AND WIND GUSTS OF 40 TO 50 MPH ARE EXPECTED WITH
THIS STORM.
LAT...LON 3590 8173 3587 8171 3586 8167 3565 8174
3574 8210 3587 8201 3589 8198 3591 8198
RWHSPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
504 PM EDT SAT AUG 20 2011
NCZ033-501-503-202145-
AVERY-BURKE MOUNTAINS-CALDWELL MOUNTAINS-
504 PM EDT SAT AUG 20 2011
...A STRONG THUNDERSTORM WILL AFFECT NORTHWESTERN BURKE...
NORTHWESTERN CALDWELL AND SOUTHERN AVERY COUNTIES THROUGH 545 PM
EDT...
AT 501 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 4 MILES EAST OF JONAS RIDGE...OR 10 MILES
SOUTHEAST OF NEWLAND...MOVING SOUTHEAST AT 10 MPH.
THIS STORM WILL BE NEAR...
GLOBE...
DIME SIZE HAIL...AND WIND GUSTS OF 40 TO 50 MPH ARE EXPECTED WITH
THIS STORM.
LAT...LON 3615 8182 3612 8181 3610 8149 3596 8160
3590 8173 3590 8191 3596 8194 3595 8196
3592 8195 3592 8199 3595 8204 3598 8206
RWHSPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
539 PM EDT SAT AUG 20 2011
NCZ064-202230-
TRANSYLVANIA-
539 PM EDT SAT AUG 20 2011
...A STRONG THUNDERSTORM WILL AFFECT TRANSYLVANIA COUNTY THROUGH 630
PM EDT...
AT 534 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM NEAR BREVARD...MOVING SOUTHEAST AT 10 MPH.
THIS STORM WILL BE NEAR...
ROSMAN...
DIME SIZE HAIL...AND WIND GUSTS OF 40 TO 50 MPH ARE EXPECTED WITH
THIS STORM.
LAT...LON 3526 8260 3522 8261 3514 8258 3512 8266
3513 8268 3510 8270 3507 8278 3508 8277
3509 8279 3527 8292 3532 8285 3532 8283
3540 8274
RWHThe Greer radar (KGSP), 58 km away, was scanning. The volume nearest the first event began at 21:43 UTC.
6 thunderstorm wind, 3 hail. Local standard time, as filed.
Large tree limbs and power lines were blown down on Island Ford Rd.
Spotter reported a carport lifted and tossed and a light pole blown down on Range Rd.
Dime to quarter size hail fell along highway 126 at Lake James.
Several large tree limbs were blown down on Shoal Creek Church Rd.
Several trees and power lines were blown down.
A tree was blown down on highway 205 near New Salem.
A tree was blown down on Ansonville Rd.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in North Carolina in 2011Every state in 2011This day in weather historyWarnings in North Carolina, August 2011
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 343557, 343572, 343574, 343576, 343578, 343745, 343746, 343747, 343748.