Training thunderstorms dropped 4 to 6 inches of rain over portions of Lancaster and Chesterfield counties flooding many roads and low lying areas. Several roads were closed and one vehicle got trapped in flooded waters.
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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.
Training thunderstorms dropped 4 to 6 inches of rain over portions of Lancaster and Chesterfield counties flooding many roads and low lying areas. Several roads were closed and one vehicle got trapped in flooded waters.
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 Sep 17, 2:16 AM EST, 2 hours 29 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE COLUMBIA SC 316 AM EDT MON SEP 17 2012 .SYNOPSIS... ATMOSPHERIC MOISTURE WILL BE ON THE INCREASE THROUGH TUESDAY AHEAD OF A COLD FRONT THAT WILL SLOWLY MOVE THROUGH LATE TUESDAY NIGHT AND WEDNESDAY. DRIER AIR IS EXPECTED TO ENTER THE REGION THURSDAY...PROVIDING FAIR WEATHER INTO SATURDAY. && .NEAR TERM /THROUGH TONIGHT/... CLOSED UPPER LOW OVER TX...WITH GENERALLY ZONAL UPPER FLOW ACROSS THE EASTERN CONUS...AND NORTHERN STREAM TROUGH DIGGING INTO THE NORTHERN PLAINS. SURFACE BOUNDARY CURRENTLY STRETCHED ACROSS THE NORTHERN PART OF OUR FORECAST AREA (FA)...WITH HIGH PRESSURE CURRENTLY CENTERED TO OUR NE OVER THE MID ATLANTIC COAST. RADAR INDICATES A FEW SHOWERS IN PROGRESS NEAR THE FRONT OVER THE NORTHERN FA. UPPER LOW WILL BEGIN TO OPEN AND SHIFT EAST TOWARDS THE LOWER MISS VALLEY THROUGH TONIGHT...WITH UPPER FLOW BECOMING SW OVER OUR REGION. LOW LEVEL FLOW OVER OUR REGION TO BECOME S TO SE AND INCREASE TODAY AND TONIGHT AS HIGH TO OUR NE SLIPS EAST AND LOW PRESSURE DEVELOPS TO OUR WEST. THIS MAY LEAD THE FRONT TO SHIFT NORTH A LITTLE...AND WILL ALSO RESULT IN INCREASING ATMOSPHERIC MOISTURE...THOUGH THE HIGHEST MOISTURE INCREASE WILL BE TO OUR WEST TODAY. HIGH RESOLUTION NEAR TERM MODELS INDICATING FRONTAL PRECIPITATION TO GRADUALLY DIMINISH AND SHIFT NORTH THROUGH THIS MORNING...WHILE ADDITIONAL SCATTERED CONVECTION TO DEVELOP WITH DIURNAL HEATING OVER THE FA LATER TODAY. WILL MENTION SLIGHT CHANCE THUNDER TO ACCOMPANY THE CHANCE POPS THIS AFTERNOON...BUT SEVERE NOT EXPECTED TODAY DUE TO WEAK INSTABILITY. GREATEST INCREASE IN ATMOSPHERIC MOISTURE AND INSTABILITY TODAY APPEARS WILL BE MAINLY JUST TO OUR WEST. SPC HAS SLIGHT RISK SEVERE MAINLY JUST TO OUR WEST. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... UPPER ENERGY AND ACCOMPANYING SURFACE LOW WILL LIFT NE FROM THE LOWER MISS VALLEY/GULF COAST REGION AHEAD OF AN APPROACHING UPPER TROUGH AND COLD FRONT. SIGNIFICANT ATMOSPHERIC MOISTURE...WITH PW VALUES 2 INCHES OR GREATER...WILL TRAVERSE OUR REGION TUESDAY. CATEGORICAL POPS CONTINUE TO APPEAR IN ORDER. THE TRACK OF BEST UPPER LIFT...SURFACE LOW...AND STRONGEST LOW LEVEL JET WILL STAY JUST TO OUR NORTH...BUT MODERATE INSTABILITY AND CONSIDERABLE LOW LEVEL JET TO PROVIDE A SEVERE THREAT WITH STRONG WIND GUSTS POSSIBLE. SPC MAINTAINS REGION IN SLIGHT RISK TUE/TUE NT. THE BEST MOISTURE WILL SHIFT TO OUR EAST TUESDAY NIGHT. COLD FRONT APPEARS TO MOVE INTO THE REGION TUE NT...BUT THEN SLOWS DOWN AS LATEST MODELS MAINTAINING UPPER TROUGHINESS JUST TO OUR WEST THROUGH WEDNESDAY...WITH A SW UPPER FLOW PARALLEL TO THE FRONT AND APPEARANCE OF SECONDARY LOW FORMATION ALONG THE FRONT NEAR OUR REGION LATE TUE NT AND EARLY WEDNESDAY. THIS WILL NOT ALLOW THE FRONT TO GET A PUSH THROUGH THE REGION...AND MAY PROVIDE FOR SOME LINGERING CLOUDINESS AND MOISTURE WEDNESDAY. && .LONG TERM /THURSDAY THROUGH SUNDAY/... NO CHANGES WERE MADE TO THE ONGOING FORECAST FOR THIS TIME PERIOD. PREVIOUS DISCUSSION FOLLOWS. THE EXTENDED FORECAST FEATURES BELOW NORMAL TEMPERATURES FOR BOTH MAXIMUM AND MINIMUM TEMPERATURES AND RELATIVELY DRY CONDITIONS. MEDIUM RANGE MODELS ARE IN REASONABLE AGREEMENT WITH THE UPPER LEVEL PATTERN THROUGH THE PERIOD. AN EXPANSIVE UPPER LEVEL TROUGH WILL BE SITUATED ACROSS MUCH OF THE COUNTRY EAST OF THE ROCKY MOUNTAINS ON THURSDAY WITH A FRONTAL BOUNDARY LOCATED JUST OFF THE EAST THE COAST. ANOTHER SURGE OF UPPER ENERGY WILL DROP INTO THE BACKSIDE OF THE UPPER TROUGH THURSDAY NIGHT AND FRIDAY...REINFORCING AND AMPLIFYING THE UPPER TROUGH AS IT PERSISTS INTO THE WEEKEND. SURFACE HIGH PRESSURE WILL BE CENTERED OVER THE NORTHEASTERN STATES THUR/FRI AND RIDGE DOWN THE EAST COAST INTO THE FORECAST AREA LIMITING PRECIPITATION CHANCES. PWAT VALUES THURSDAY THROUGH SATURDAY WILL REMAIN LOW...LESS THAN OR AROUND AN INCH...FURTHER LIMITING PRECIPITATION CHANCES. THE UPPER TROUGH AXIS SHIFTS CLOSER TO THE FORECAST AREA OVER THE WEEKEND AS ATMOSPHERIC MOISTURE INCREASES WITH PWAT VALUES RETURNING TO AROUND 1.5 INCHES. ATMOSPHERE BECOMES A BIT MORE UNSTABLE WITH HEATING OF THE MODIFIED AIR MASS AND INCREASED MOISTURE AND WILL INCLUDE SLIGHT CHANCE POPS ON SUNDAY AS A FRONTAL BOUNDARY APPROACHES THE REGION. IT IS WORTH NOTING THAT THERE IS A DIFFERENCE BETWEEN THE ECMWF/GFS WHERE THE ECMWF BRINGS A CLOSED LOW ACROSS THE WESTERN OHIO VALLEY BY SUNDAY. MAX TEMPERATURES ARE EXPECTED IN THE LOWER 80S THUR/FRI AND POSSIBLY REACH THE MID 80S NEXT WEEKEND WHILE OVERNIGHT LOWS SHOULD BE IN THE LOWER 60S WITH SOME POSSIBLE UPPER 50S THUR/FRI MORNING. && .AVIATION /07Z MONDAY THROUGH FRIDAY/... WEAK ONSHORE FLOW CONTINUES BUT WEAK FRONTAL BOUNDARY REMAINS WELL NORTH OF TAF SITES. ONLY IFR CONDITIONS ARE NEAR THE CLT AREA TO THE NORTH OF FRONT WHERE THERE IS WEAK ISENTROPIC LIFT. ACROSS REGION FROM GEORGIA INTO SOUTH CAROLINA JUST MID LEVEL CEILINGS AROUND 10 KFT. THERE ARE ALSO SOME LIGHT SHOWERS NORTH OF TAF SITES BUT SHOULD NOT MOVE INTO AREA LATER CLOSE TO DAYBREAK. DUE TO UNCERTAINTY AS TO TIMING AND COVERAGE...DECIDED NOT TO MENTION. ALSO...WILL KEEP CONDITIONS ABOVE IFR. MODELS BRING IFR CONDITIONS IN BY 12Z. WEAK FRONTAL BOUNDARY IS EXPECTED TO DRIFT FARTHER NORTHWARD WITH LITTLE AFFECT ON TAF SITES. SREF IFR PROBABILITIES GIVE LESS THAN A 20 PERCENT CHANCE OF IFR CEILINGS THIS MORNING. IN ADDITION SATELLITE IMAGERY SHOWS A GOOD SWATHE OF MID LEVEL CLOUDS CONTINUING TO MOVE EASTWARD ACROSS THE REGION. WILL START WITH VFR CONDITIONS GRADUALLY LOWERING TO MVFR WITH CEILINGS 1-2 KFT AND VSBYS 3-4 MILES IN FOG FOR A BRIEF PERIOD 12Z-15Z THIS MORNING. AFTER 15Z...MAINLY VFR CONDITIONS. THERE WILL PROBABLY BE SOME SHOWERS AND MAY A THUNDERSTORM OR TWO LATER THIS AFTERNOON ON INTO THE EARLY EVENING HOURS. SPC JUST HAS AREA IN SEE TEXT. DECIDED NOT MENTION IN TAF SITES DUE TO UNCERTAINTY AS TO TIMING AND COVERAGE. LATER THIS EVENING AS MOISTURE INCREASES TO THE FORECAST AREA...DECIDED TO GO MVFR CEILINGS AROUND 2 KFT. SURFACE VSBYS EXPECTED TO REMAIN 7 MILES AS SURFACE WINDS SHOULD BE 5-6 KNOTS. HOWEVER...THERE COULD BE BRIEF IFR-MVFR CONDITIONS IN SHOWERS OR POSSIBLY A THUNDERSTORM. AGAIN...DID NOT MENTION DUE TO UNCERTAINTY. EXTENDED AVIATION OUTLOOK...WIDESPREAD MVFR OR IFR CONDITIONS MAY OCCUR MONDAY NIGHT INTO WEDNESDAY ASSOCIATED WITH A SLOW MOVING FRONTAL SYSTEM. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...NONE. GA...NONE. && DCM/TTH
The Columbia radar (KCAE), 92 km away, was scanning. The volume nearest the first event began at 09:43 UTC.
16 flash flood. Local standard time, as filed.
Lancaster spotter reported flash flooding from Lancaster to the NC State Line on SC 200. The worst flooding was near the intersection of Hwy 200 and Hwy 521.
One to two feet of water covered portions of Hwy 522.
Water covering the bridge along Hwy 9 near the Lancaster Chesterfield county line. Many other roads including Doster road also flooded and closed.
Public reported that Tradesville road was flooded and impassable.
Sheriff reported Carnes Wilson road was flooded and impassable.
Sheriff reported Hershel Plyer Road and Gills Creek Drive flooded and impassable.
Highway Patrol reported Taxahaw and Rocky River roads closed due to flooding.
Broadcast media reported a car trapped in flood water on Cimmeron road off Rocky River road. Dixie School road also closed due flooded waters.
Lancaster County EM reported a car washed off of Catoe Road.
Lancaster County EM reported a water rescue of patrons in a vehicle on Langley road.
Sheriff reported numerous roads flooded in central Lancaster County.
Broadcast media reported Hough Road flooded near the 2200 block.
Sheriff reported Taxahaw road still flooded and impassable.
Sheriff reported Hershel Plyer road still impassable do to flood waters.
EM reported flooded roads with closures on the west end of the county between Jefferson and Pageland.
Sheriff reported Hannahs Creek out of its banks and flooding Independence Park and Constitutional Park.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in South Carolina in 2012Every state in 2012This day in weather historyWarnings in South Carolina, September 2012
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: 401313, 401314, 401315, 401317, 401318, 401319, 401320, 401321, 401322, 401323, 401324, 401325, 401326, 401327, 401335, 401328.