A passing shortwave and numerous outflow boundaries produced scatterd showers and thunderstorms. A couple of these storms reached severe limits.
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 CAE wrote it up.
A passing shortwave and numerous outflow boundaries produced scatterd showers and thunderstorms. A couple of these storms reached severe limits.
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 Columbia, SC wrote its last area forecast discussion before the first event at Aug 20, 12:56 PM EST, 2 hours 9 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE COLUMBIA SC 156 PM EDT SAT AUG 20 2011 .SYNOPSIS... SCATTERED MAINLY AFTERNOON AND EVENING THUNDERSTORMS ARE EXPECTED THROUGH MONDAY AS MOISTURE INCREASES ACROSS THE AREA. A WEAK COLD FRONT WILL MOVE SLOWLY ACROSS THE REGION MONDAY AFTERNOON. DRIER AIR WILL FILTER IN BEHIND THE FRONT THROUGH TUESDAY. && .NEAR TERM /THROUGH TONIGHT/... MODELS AND SATELLITE WATER VAPOR IMAGERY INDICATE UPPER SHORT WAVE CURRENTLY IN OUR VICINITY WHICH WILL SLOWLY PUSH TOWARDS THE COAST TODAY. MID LEVEL CLOUD COVER WILL IMPEDE HEATING SOME INITIALLY BUT BETTER INSOLATION MAY OCCUR LATER THIS AFTERNOON. THOUGH SOME NVA BEHIND THE SHORT WAVE ALONG WITH DRY AIR ALOFT MAY WORK AGAINST CONVECTIVE COVERAGE...INDICATIONS OF CONSIDERABLE LOW LEVEL MOISTURE PLUS PROMISE OF MODERATE INSTABILITY IN DIURNAL HEATING PROVIDES SOME CHANCE OF CONVECTION. WILL MAINTAIN SLIGHT CHANCE TO CHANCE POPS. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... IN GENERAL THE REGION WILL REMAIN UNDER THE SAME UPPER FLOW AS THE PAST FEW DAYS. THIS MEANS AN EAST COAST TROUGH...WITH MAIN UPPER HIGH RESIDING OVER THE LOWER PLAINS STATES. NORTHWEST FLOW ALOFT...AND ONSHORE FLOW AT THE SURFACE. MODELS SHOW AN INCREASE IN LOW LEVEL MOISTURE WITH PRECIPITABLE WATER LIKELY ABOVE 2.00 INCHES BY SUNDAY AFTERNOON. WITH MODERATE INSTABILITY AND SHORT WAVE TROUGH APPROACHING...EXPECT SCATTERED AFTERNOON AND EVENING THUNDERSTORMS. TEMPERATURES SHOULD BE ON THE HIGH SIDE OF MAXIMUM TEMPERATURE GUIDANCE SUNDAY DUE TO LOW LEVEL WARM ADVECTION AHEAD OF APPROACHING FRONT. FRONT SLOWLY MOVING ACROSS THE REGION MONDAY...MAY HANG UP IN THE SOUTHEAST MIDLANDS OR UNDERGO FRONTOLYSIS. DEEPER MOISTURE SHIFTING EAST OF THE AREA...BUT WITH MODERATE TO STRONG INSTABILITY SOUTHEAST MIDLANDS THINK SCATTERED STORMS IN THAT AREA...SO WENT ABOVE MOS GUIDANCE THERE...ELSWHERE...DIMINISHING THREAT FOR THUNDERSTORMS. && .LONG TERM /TUESDAY THROUGH SATURDAY/... UPPER RIDGE REMAINS CENTERED OVER THE SOUTHERN PLAINS WITH WITH A WEAK UPPER TROUGH OVER THE EAST COAST THROUGH MID-WEEK. APPEARS DRIER AIR ACROSS THE AREA TUESDAY AND TRIGGER LACKING...SO NO POPS FORECAST. ENSEMBLE GUIDANCE SUGGESTS AN INCREASE IN DIURNAL CONVECTION BY LATE WEEK AS MOISTURE INCREASES. LOTS OF UNCERTAINTIES WITH FUTURE TRACK OF TROPICAL WAVE NOW ENTERING EASTERN CARIBBEAN WHICH MAY HAVE AN INFLUENCE ON OUR WEATHER BY END OF THE PERIOD. TEMPERATURES AT OR JUST ABOVE CLIMATOLOGY. && .AVIATION /17Z SATURDAY THROUGH WEDNESDAY/... VFR CONDITIONS CURRENTLY WITH SCT TO BKN MID LEVEL CLOUD COVER. DAYTIME HEATING AND MODERATE INSTABILITIES EXPECTED TO RESULT IN AT LEAST A SLIGHT CHANCE OF AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS...BUT CONFIDENCE TOO LOW TO INCLUDE MENTION IN THE TAFS AT THIS TIME. FOG POSSIBLE LATE TONIGHT/EARLY SUNDAY MORNING DEPENDING ON CLOUD COVER. WILL MENTION MAINLY MVFR VSBYS AT THIS TIME AT THE MOST FAVORED LOCATIONS AGS/OGB...IN LINE WITH LATEST GUIDANCE. EXTENDED AVIATION OUTLOOK...MVFR OR IFR CONDITIONS MAY OCCUR IN EARLY MORNING FOG/STRATUS AS WELL AS IN AFTERNOON AND EVENING CONVECTION EACH DAY. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...NONE. GA...NONE. && SYNOPSIS... NEAR TERM...07 SHORT TERM... LONG TERM... AVIATION...31
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE COLUMBIA SC 433 AM EDT SAT AUG 20 2011 GAZ040-063>065-077-SCZ015-016-018-020>022-025>031-035>038-041-210845- LINCOLN-MCDUFFIE-COLUMBIA-RICHMOND-BURKE-LANCASTER-CHESTERFIELD- MCCORMICK-NEWBERRY-FAIRFIELD-KERSHAW-EDGEFIELD-SALUDA-LEXINGTON- RICHLAND-LEE-AIKEN-SUMTER-BARNWELL-ORANGEBURG-CALHOUN-CLARENDON- BAMBERG- 433 AM EDT SAT AUG 20 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR EAST CENTRAL GEORGIA AND CENTRAL SOUTH CAROLINA. .DAY ONE...TODAY AND TONIGHT. NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY. NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE COLUMBIA SC
310 PM EDT SAT AUG 20 2011
SCZ026-027-030-202000-
AIKEN-LEXINGTON-SALUDA-
310 PM EDT SAT AUG 20 2011
...STRONG THUNDERSTORMS WILL IMPACT PORTIONS OF LEXINGTON...SALUDA
AND AIKEN COUNTIES THROUGH 400 PM EDT...
AT 305 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM...NEAR MONETTA...MOVING EAST AT 15 TO 20 MPH.
SOME LOCATIONS THAT WILL BE AFFECTED INCLUDE...
BATESBURG...LEESVILLE AND RIDGE SPRING...
PREPARE NOW FOR THE FOLLOWING HAZARDS...
GUSTY WINDS OF 40 TO 50 MPH...
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REPORT LARGE HAIL...DAMAGING WINDS OR FLOODING TO YOUR COUNTY
SHERIFF...OR CALL THE NATIONAL WEATHER SERVICE TOLL FREE AT 1...8 7
7...6 3 3...6 7 7 2.
&&
LAT...LON 3390 8167 3402 8130 3369 8126 3376 8163
3380 8167 3381 8165 3382 8168 3383 8169
TIME...MOT...LOC 1911Z 260DEG 19KT 3385 8153SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE COLUMBIA SC
344 PM EDT SAT AUG 20 2011
SCZ027-030-035-036-041-202045-
AIKEN-BAMBERG-BARNWELL-LEXINGTON-ORANGEBURG-
344 PM EDT SAT AUG 20 2011
...STRONG THUNDERSTORMS WILL IMPACT PORTIONS OF BAMBERG...
LEXINGTON...AIKEN...ORANGEBURG AND BARNWELL COUNTIES THROUGH 445 PM
EDT...
AT 336 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
CLUSTER OF STRONG THUNDERSTORMS...ALONG A LINE EXTENDING FROM
WAGENER TO WILLISTON TO OLAR. THESE STORMS WERE MOVING DRIFTING EAST
AT 10 MPH.
SOME LOCATIONS THAT WILL BE AFFECTED INCLUDE...
BAMBERG...BARNWELL...BLACKVILLE...DENMARK AND WILLISTON...
PREPARE NOW FOR THE FOLLOWING HAZARDS...
GUSTY WINDS OF 40 TO 50 MPH...
PEA SIZE HAIL...
LOCALLY HEAVY RAIN WITH AMOUNTS FROM 1 TO 2 INCHES...
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REPORT LARGE HAIL...DAMAGING WINDS OR FLOODING TO YOUR COUNTY
SHERIFF...OR CALL THE NATIONAL WEATHER SERVICE TOLL FREE AT 1...8 7
7...6 3 3...6 7 7 2.
&&
LAT...LON 3342 8159 3376 8140 3383 8113 3377 8106
3375 8106 3375 8103 3374 8101 3372 8101
3371 8104 3367 8101 3348 8099 3318 8078
3315 8084 3309 8117
TIME...MOT...LOC 1943Z 270DEG 2KT 3369 8134 3345 8138
3315 8117SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE COLUMBIA SC
403 PM EDT SAT AUG 20 2011
SCZ038-202100-
CLARENDON-
403 PM EDT SAT AUG 20 2011
...STRONG THUNDERSTORMS WILL IMPACT PORTIONS OF CLARENDON COUNTY
THROUGH 500 PM EDT...
AT 359 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM...OVER CLARENDON COUNTY. LITTLE MOVEMENT WAS
NOTED.
SOME LOCATIONS THAT WILL BE AFFECTED INCLUDE...
LAKE MARION AND JORDAN.
PREPARE NOW FOR THE FOLLOWING HAZARDS...
GUSTY WINDS OF 40 TO 50 MPH...
FREQUENT CLOUD TO GROUND LIGHTNING...
TORRENTIAL RAIN WHICH MAY PRODUCE LOCALIZED FLOODING...
PRECAUTIONARY/PREPAREDNESS ACTIONS...
THUNDERSTORMS POSE A VARIETY OF THREATS TO BOATERS ON LAKE MARION.
YOUR BEST COURSE OF ACTION DURING A THUNDERSTORM IS TO SEEK SAFE
HARBOR. IF YOU ARE CAUGHT IN THE OPEN LAKE WATERS...STAY BELOW
DECK...AND IF POSSIBLE...AWAY FROM UNGROUNDED METAL OBJECTS.
HEAVY RAINS MAY FLOOD LOW LYING AREAS SUCH AS DITCHES AND
UNDERPASSES. AVOID THESE AREAS AND DO NOT CROSS FLOODED ROADS AS THEY
MAY BE WASHED OUT. WATER LEVELS OF SMALL STREAMS AND RIVERS MAY ALSO
RISE...THEREFORE SEEK HIGHER GROUND IF THREATENED BY FLOOD WATERS.
REPORT LARGE HAIL...DAMAGING WINDS OR FLOODING TO YOUR COUNTY
SHERIFF...OR CALL THE NATIONAL WEATHER SERVICE TOLL FREE AT 1...8 7
7...6 3 3...6 7 7 2.
&&
LAT...LON 3351 8010 3348 8014 3347 8014 3345 8017
3344 8023 3345 8024 3345 8025 3344 8027
3345 8028 3344 8031 3361 8032 3362 8007
TIME...MOT...LOC 2002Z 355DEG 8KT 3352 8017The Columbia radar (KCAE), 32 km away, was scanning. The volume nearest the first event began at 20:04 UTC.
3 thunderstorm wind. Local standard time, as filed.
Several medium to large limbs down on Cedar Creek Road near Yogi Bear Campground.
Tri-County Electric reported outages due to downed power lines.
Highway patrol reported a tree down along highway 66 two miles west of the elementary school.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in South Carolina in 2011Every state in 2011This day in weather historyWarnings in South 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: 324081, 324098, 324083.