Lines of thunderstorms producing heavy rain repeatedly passed over the same areas in the Midlands. Up to 5 inches of rainfall produced flash flooding in low-lying and urban areas.
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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.
Lines of thunderstorms producing heavy rain repeatedly passed over the same areas in the Midlands. Up to 5 inches of rainfall produced flash flooding in low-lying and urban areas.
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 22, 7:08 AM EST, 6 hours 17 minutes earlier.
Area Forecast Discussion National Weather Service Columbia SC 808 AM EDT Sun Aug 22 2021 .SYNOPSIS... An upper trough over the Mid-Atlantic region will begin to lift northeastward away from the region today but upper disturbances rotating through the base of the trough will provide showers and thunderstorms again today. The upper ridge over the middle of the country will build eastward early next week bringing a return to typical summer like conditions. && .NEAR TERM /THROUGH TONIGHT/... A weak shortwave is moving through the lower half of the CWA with mostly weak but widespread showers. This shortwave is moving around the base of an upper level low located just west of the Delmarva Peninsula. Moisture will continue to deepen through the day with PWATs rising well over 2 inches across the entire forecast area. Shortwave energy will slowly traverse the forecast area through the day taking advantage of the abundant moisture in place and diurnal heating to provide widespread showers and thunderstorms. Hi-res guidance in reasonable agreement with this scenario and MOS guidance pops have also increased over the past few runs. Severe threat again looks low today given very moist adiabatic soundings and deep moisture in place, but heavy rain could be a concern, especially given the amount of rain that occurred late Saturday and early this morning across portions of the forecast area. Again, chances of rain will likely linger into the evening and overnight hours with the shortwave energy slow to move through the region, so will hold on to some chance pops through 06z or so before diminishing them late tonight. Temperatures today should be cooler than the past few days with expected widespread cloud cover and precipitation. Expect highs in the mid to upper 80s. Tonight, temperatures will again be limited by cloud cover with some convective debris clouds early and stratus likely to develop during the predawn hours. Overnight lows expected in the lower 70s. && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... Behind the upper short wave, drier air is progged to shift south into the region Monday. The NE upper low will open and shift NE with a trailing trough axis along the east coast. Both GFS and EC ensemble means indicate lower precipitable water (PW) values entering the region, with generally below climatological normal PW values for most of the FA Monday, with some moisture increase noted Tuesday afternoon. Forecast soundings indicate high LFC heights and convect temps, and latest guidance POPs, including NBM, on the low side, Monday, with some increase Tuesday. && .LONG TERM /TUESDAY THROUGH SATURDAY/... The upper trough along the east coast is expected to weaken, leaving a general weakness between two upper high centers, one to our west and another to our east offshore. Latest guidance indicates an upper low to move clockwise around the southern periphery of the offshore high and move towards the SE coast. Some slight difference in model solutions with this feature. 18z EC ensemble mean takes the system into our region, while the 00Z GFS ensemble mean takes it more into FL/GA. Regardless, it appears atmospheric moisture will be on the increase for our FA Wednesday, and NBM POPs have responded by trending upward into the likely range. Late in the forecast period, the feature will move west, leaving behind some weak upper ridging, with PW values progged near seasonal normals, providing an expectation of typical summerlike weather with scattered mainly diurnal showers and thunderstorms. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... Widespread but weak showers have become widespread across the area. Low clouds will linger through mid morning with VFR returning this afternoon outside of visibility restrictions via showers. This afternoon, during peak daytime heating, widespread thunderstorms will pose IFR vsby and MVFR cig restrictions. Winds light and variable through the morning then picking up to 5-10kt in the afternoon. EXTENDED AVIATION OUTLOOK...Late night/early morning fog/stratus restrictions possible Monday as moisture returns. Mainly afternoon and evening convection along with associated restrictions possible each day. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && SYNOPSIS... NEAR TERM... SHORT TERM... LONG TERM... AVIATION...
Hazardous Weather Outlook National Weather Service Columbia SC 420 AM EDT Sun Aug 22 2021 GAZ040-063>065-077-SCZ016-018-020>022-025>031-035-037-038-041-115- 116-135>137-230830- Lincoln-McDuffie-Columbia-Richmond-Burke-Chesterfield-McCormick- Newberry-Fairfield-Kershaw-Edgefield-Saluda-Lexington-Richland-Lee- Aiken-Sumter-Barnwell-Calhoun-Clarendon-Bamberg-Northern Lancaster- Southern Lancaster-Northwestern Orangeburg-Central Orangeburg- Southeastern Orangeburg- 420 AM EDT Sun Aug 22 2021 This Hazardous Weather Outlook is for the Midlands of South Carolina and the Central Savannah River area of Georgia. .DAY ONE...Today and tonight. The probability for widespread hazardous weather is low. .DAYS TWO THROUGH SEVEN...Monday through Saturday. The probability for widespread hazardous weather is low. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
The Columbia radar (KCAE), 4 km away, was scanning. The volume nearest the first event began at 18:23 UTC.
3 flash flood. Local standard time, as filed.
Spotter posted social media report via Twitter of a stranded vehicle under water and roadway flooded along Circle Street in the Cayce, SC community.
Emergency Manager and multiple public reports of roadway impassable and closed due to flooding on Charleston Highway and Gardner's Terrace Road.
Public report of nearly impassable roadway due to flooding at 12th Street and Old Wire Road.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in South Carolina in 2021Every state in 2021This day in weather historyWarnings in South Carolina, August 2021
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: 969976, 969977, 969978.