Flash Flood Warnings in South Dakota, 2009

By month

22 of 44 flash flood warnings covering South Dakota in 2009 had a flash flood report inside them; 30 of 39 flash flood reports fell inside a warning, on average 56 minutes after it went out.

South Dakota, 2009

Each office's whole area, 2009

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.

• Union County9
• Brown County6
• Pennington County4
• Edmunds County4
• Codington County3
• Grant County3
• Hamlin County3
• Dewey County3
• Day County3
• Spink County3
• Clay County3
• McPherson County3
• Deuel County2
• Kingsbury County2
• Lincoln County2
• Minnehaha County2
• Meade County2
• Custer County2
• Corson County2
• Yankton County2
• Hughes County2
• Brookings County1
• Lake County1
• Miner County1
• Turner County1
• Harding County1
• Perkins County1
• Fall River County1
• Butte County1
• Lawrence County1
• Bon Homme County1
• Charles Mix County1
• Douglas County1
• Hutchinson County1
• Clark County1
• Faulk County1
• Marshall County1
• Potter County1
• Buffalo County1
• Hand County1

1. March 23, 20095flash flood warnings
2. June 15, 20095flash flood warnings
3. June 16, 20095flash flood warnings
4. June 14, 20094flash flood warnings
5. July 8, 20094flash flood warnings
6. July 14, 20093flash flood warnings
7. June 18, 20092flash flood warnings
8. July 9, 20092flash flood warnings
9. August 19, 20092flash flood warnings
10. March 25, 20091flash flood warnings
11. April 14, 20091flash flood warnings
12. May 25, 20091flash flood warnings

Alerts in force nowTornadoes on recordThe radar archive20082010

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.