Flash Flood Warnings in South Dakota, 2011

By month

33 of 67 flash flood warnings covering South Dakota in 2011 had a flash flood report inside them; 47 of 56 flash flood reports fell inside a warning, on average 95 minutes after it went out.

South Dakota, 2011

Each office's whole area, 2011

An office's figures cover every county it serves, including across state lines.

Verified by the Iowa Environmental Mesonet's Cow, which matches each storm-based warning with the local storm reports inside its polygon while it was in force, within 15 km of its edge: a tornado warning counts as verified on a tornado report, a severe thunderstorm warning on hail of 1 inch or more, a gust of 58 mph or more, or wind damage, a flash flood warning on a flash flood report. The false alarm ratio is the share of warnings with no such report; "inside a warning" is the probability of detection, the share of reports that fell inside one; lead time runs from the warning's issue to each report inside it, counting zero for a report that came first. A warning with no report is not proof nothing happened: reports come from spotters, the public and damage surveys, and are thin where few people live.

• Minnehaha County8
• Stanley County7
• Perkins County6
• Lincoln County6
• Hughes County6
• Custer County5
• Fall River County5
• Moody County5
• Brown County5
• Aurora County4
• Potter County4
• Charles Mix County4
• Union County4
• Meade County3
• Jackson County3
• Todd County3
• Dewey County3
• Brule County3
• Gregory County3
• Hyde County3
• Lyman County3
• Ziebach County2
• Pennington County2
• Campbell County2
• Walworth County2
• Turner County2
• Douglas County2
• Jerauld County2
• Buffalo County2
• Sully County2
• Mellette County2
• Butte County2
• Lawrence County2
• Marshall County2
• Harding County2
• Roberts County2
• Davison County1
• Hanson County1
• Miner County1
• Sanborn County1

1. July 5, 20118flash flood warnings
2. June 14, 20115flash flood warnings
3. June 21, 20115flash flood warnings
4. May 10, 20113flash flood warnings
5. July 1, 20113flash flood warnings
6. July 27, 20113flash flood warnings
7. June 11, 20112flash flood warnings
8. June 13, 20112flash flood warnings
9. June 20, 20112flash flood warnings
10. June 25, 20112flash flood warnings
11. June 26, 20112flash flood warnings
12. July 3, 20112flash flood warnings

Alerts in force nowTornadoes on recordThe radar archive20102012

National Weather Service watches, warnings, advisories and statements from the Iowa Environmental Mesonet's VTEC archive, which reconstructs tornado, severe thunderstorm, flash flood and marine warnings back to 1986 from the NWS text archive. Storm Prediction Center watches and mesoscale discussions from SPC's archive through the Mesonet. County centers from the US Census Bureau. Warning verification from the Mesonet's Cow. Rebuilt daily.