Alert archive / South Dakota / Union County
Weather alerts in Union County, South Dakota, 2011
126 weather alerts in 2011, from the National Weather Service and the Storm Prediction Center. An alert counts here when it covered this county.
Union County and its neighbors
Each county as a circle sized by its count in 2011. Tap one for its archive.
- Alerts
- 126
- Warnings
- 53
- Watches
- 15
- Advisories
- 36
- Busiest month
- May25 alerts
- Busiest day
- August 18, 20119 alerts
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
0 of 2 tornado warnings covering Union County in 2011 had a tornado report inside them.
Union County, 2011
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 2 | 0 | 100% | 0 | ||
| Severe thunderstorm warnings | 26 | 21 | 19% | 3 | 100% | 21 min |
| Flash flood warnings | 4 | 3 | 25% | 0 |
Each office's whole area, 2011
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Sioux Falls, SD: tornado warnings | 38 | 10 | 74% | 15 | 73% | 12 min |
| NWS Sioux Falls, SD: severe thunderstorm warnings | 274 | 187 | 32% | 337 | 89% | 19 min |
| NWS Sioux Falls, SD: flash flood warnings | 36 | 26 | 28% | 54 | 91% | 61 min |
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.
The alerts
Every alert, in the order issued. Times are local, Central Time. Each opens its own page with the text, the map, the radar and the sounding.
| Issued | Product | Office | Lasted |
|---|---|---|---|
| Jan 1, 3:28 AM CST | Wind Chill Advisory | FSD | 9 hr |
| Jan 7, 10:00 AM CST | Wind Advisory | FSD | 6 hr |
| Jan 8, 2:24 PM CST | Winter Weather Advisory | FSD | 64 hr |
| Jan 11, 3:14 PM CST | Wind Chill Advisory | FSD | 19 hr |
| Jan 16, 9:45 PM CST | Winter Weather Advisory | FSD | 6 hr |
| Jan 28, 9:09 AM CST | Dense Fog Advisory | FSD | 3 hr |
| Jan 29, 3:39 PM CST | Winter Weather Advisory | FSD | 3 days |
| Jan 31, 3:17 PM CST | Wind Chill Warning | FSD | 45 hr |
| Feb 2, 2:58 PM CST | Wind Chill Advisory | FSD | 15 hr |
| Feb 7, 3:48 AM CST | Wind Chill Advisory | FSD | 32 hr |
| Feb 8, 2:37 PM CST | Wind Chill Advisory | FSD | 21 hr |
| Feb 16, 5:55 PM CST | Dense Fog Advisory | FSD | 16 hr |
| Feb 18, 4:18 AM CST | Winter Storm Watch | FSD | 35 hr |
| Feb 18, 1:31 PM CST | River Flood Warning | FSD | 45 hr |
| Feb 18, 1:31 PM CST | River Flood Warning | FSD | 4 days |
| Feb 19, 3:37 PM CST | Ice Storm Warning | FSD | 24 hr |
| Mar 10, 3:56 AM CST | Dense Fog Advisory | FSD | 7 hr |
| Mar 11, 4:00 AM CST | Wind Advisory | FSD | 32 hr |
| Mar 14, 9:18 AM CDT | Dense Fog Advisory | FSD | 3 hr |
| Mar 15, 1:17 PM CDT | River Flood Watch | FSD | 6 days |
| Mar 15, 1:17 PM CDT | River Flood Watch | FSD | 6 days |
| Mar 16, 11:32 AM CDT | River Flood Warning | FSD | 54 days |
| Mar 16, 11:32 AM CDT | River Flood Warning | FSD | 53 days |
| Mar 21, 10:05 PM CDT | Mesoscale Discussion | SPC | 115 min |
| Apr 3, 4:17 AM CDT | Wind Advisory | FSD | 36 hr |
| Apr 9, 5:48 PM CDT | Tornado Watch | SPC | 7 hr |
| Apr 9, 8:19 PM CDT | Severe Thunderstorm Warning | FSD | 41 min |
| Apr 9, 9:06 PM CDT | Mesoscale Discussion | SPC | 54 min |
| Apr 9, 9:15 PM CDT | Severe Thunderstorm Warning | FSD | 30 min |
| Apr 9, 9:17 PM CDT | Severe Thunderstorm Warning | FSD | 43 min |
| Apr 9, 9:31 PM CDT | Tornado Warning | FSD | 29 min |
| Apr 29, 3:12 AM CDT | Wind Advisory | FSD | 16 hr |
| Apr 29, 9:11 PM CDT | Wind Advisory | FSD | 28 hr |
| May 1, 3:55 AM CDT | Wind Advisory | FSD | 13 hr |
| May 8, 9:11 PM CDT | River Flood Warning | FSD | 12 hr |
| May 11, 4:51 PM CDT | Severe Thunderstorm Warning | FSD | 39 min |
| May 11, 4:55 PM CDT | Severe Thunderstorm Warning | FSD | 50 min |
| May 11, 5:03 PM CDT | Mesoscale Discussion | SPC | 57 min |
| May 11, 5:37 PM CDT | Severe Thunderstorm Warning | FSD | 38 min |
| May 11, 5:42 PM CDT | Severe Thunderstorm Warning | FSD | 48 min |
| May 11, 6:13 PM CDT | Tornado Warning | FSD | 32 min |
| May 11, 6:29 PM CDT | Severe Thunderstorm Warning | FSD | 31 min |
| May 15, 3:18 PM CDT | Frost Advisory | FSD | 17 hr |
| May 20, 9:18 AM CDT | River Flood Warning | FSD | 19 days |
| May 20, 9:18 AM CDT | River Flood Warning | FSD | 18 days |
| May 21, 12:51 PM CDT | Mesoscale Discussion | SPC | 114 min |
| May 21, 6:47 PM CDT | Severe Thunderstorm Warning | FSD | 28 min |
| May 21, 7:38 PM CDT | Severe Thunderstorm Warning | FSD | 37 min |
| May 21, 7:49 PM CDT | Severe Thunderstorm Warning | FSD | 26 min |
| May 24, 3:22 PM CDT | Flash Flood Watch | FSD | 22 hr |
| May 24, 3:30 PM CDT | Wind Advisory | FSD | 27 hr |
| May 27, 10:31 AM CDT | River Flood Warning | FSD | 116 days |
| May 29, 3:54 PM CDT | Wind Advisory | FSD | 27 hr |
| May 29, 9:24 PM CDT | Mesoscale Discussion | SPC | 96 min |
| May 29, 10:58 PM CDT | Severe Thunderstorm Watch | SPC | 6 hr |
| May 30, 8:37 PM CDT | Severe Thunderstorm Watch | SPC | 5 hr |
| May 30, 10:38 PM CDT | Mesoscale Discussion | SPC | 2 hr |
| May 31, 10:10 AM CDT | River Flood Warning | FSD | 86 days |
| Jun 1, 5:46 PM CDT | Severe Thunderstorm Warning | FSD | 29 min |
| Jun 5, 9:58 AM CDT | River Flood Warning | FSD | 78 days |
| Jun 9, 4:06 PM CDT | River Flood Warning | FSD | 62 days |
| Jun 14, 7:58 PM CDT | River Flood Warning | FSD | 17 days |
| Jun 14, 7:58 PM CDT | River Flood Warning | FSD | 18 days |
| Jun 17, 6:44 PM CDT | Mesoscale Discussion | SPC | 91 min |
| Jun 19, 3:40 AM CDT | Flash Flood Watch | FSD | 55 hr |
| Jun 20, 6:17 PM CDT | Mesoscale Discussion | SPC | 58 min |
| Jun 20, 6:53 PM CDT | Tornado Watch | SPC | 6 hr |
| Jun 20, 8:07 PM CDT | Severe Thunderstorm Warning | FSD | 38 min |
| Jun 20, 9:02 PM CDT | Mesoscale Discussion | SPC | 58 min |
| Jun 20, 9:12 PM CDT | Severe Thunderstorm Warning | FSD | 33 min |
| Jun 20, 9:18 PM CDT | Flash Flood Warning | FSD | 2 hr |
| Jun 26, 6:16 AM CDT | Mesoscale Discussion | SPC | 59 min |
| Jun 26, 6:55 PM CDT | Flash Flood Warning | FSD | 3 hr |
| Jun 26, 7:27 PM CDT | Flash Flood Warning | FSD | 3 hr |
| Jun 26, 8:58 PM CDT | High Wind Warning | FSD | 4 hr |
| Jun 29, 3:18 PM CDT | Heat Advisory | FSD | 28 hr |
| Jul 1, 12:59 PM CDT | Mesoscale Discussion | SPC | 61 min |
| Jul 5, 3:32 PM CDT | Mesoscale Discussion | SPC | 88 min |
| Jul 10, 9:55 AM CDT | River Flood Warning | FSD | 14 days |
| Jul 10, 9:55 AM CDT | River Flood Warning | FSD | 13 days |
| Jul 10, 10:27 PM CDT | Mesoscale Discussion | SPC | 63 min |
| Jul 10, 11:56 PM CDT | Severe Thunderstorm Watch | SPC | 4 hr |
| Jul 11, 12:32 AM CDT | Severe Thunderstorm Warning | FSD | 43 min |
| Jul 11, 1:04 AM CDT | Severe Thunderstorm Warning | FSD | 41 min |
| Jul 11, 1:20 AM CDT | Severe Thunderstorm Warning | FSD | 40 min |
| Jul 12, 2:09 AM CDT | Mesoscale Discussion | SPC | 66 min |
| Jul 14, 3:31 PM CDT | Excessive Heat Watch | FSD | 12 hr |
| Jul 15, 3:42 AM CDT | Excessive Heat Warning | FSD | 6 days |
| Jul 22, 3:00 PM CDT | Mesoscale Discussion | SPC | 90 min |
| Jul 22, 3:01 PM CDT | Heat Advisory | FSD | 29 hr |
| Jul 27, 9:39 AM CDT | River Flood Warning | FSD | 3 days |
| Jul 27, 9:39 AM CDT | River Flood Warning | FSD | 4 days |
| Jul 30, 3:33 PM CDT | Heat Advisory | FSD | 52 hr |
| Aug 6, 2:58 PM CDT | Mesoscale Discussion | SPC | 3 hr |
| Aug 7, 7:49 PM CDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Aug 7, 10:28 PM CDT | Mesoscale Discussion | SPC | 2 hr |
| Aug 7, 10:33 PM CDT | Severe Thunderstorm Warning | FSD | 57 min |
| Aug 7, 11:10 PM CDT | Flash Flood Warning | FSD | 80 min |
| Aug 7, 11:12 PM CDT | Severe Thunderstorm Warning | FSD | 48 min |
| Aug 11, 6:38 PM CDT | Mesoscale Discussion | SPC | 97 min |
| Aug 11, 7:19 PM CDT | Severe Thunderstorm Watch | SPC | 5 hr |
| Aug 11, 9:42 PM CDT | Mesoscale Discussion | SPC | 63 min |
| Aug 18, 12:31 PM CDT | Mesoscale Discussion | SPC | 89 min |
| Aug 18, 1:27 PM CDT | Severe Thunderstorm Watch | SPC | 8 hr |
| Aug 18, 3:42 PM CDT | Severe Thunderstorm Warning | FSD | 48 min |
| Aug 18, 4:26 PM CDT | Severe Thunderstorm Warning | FSD | 49 min |
| Aug 18, 5:22 PM CDT | Severe Thunderstorm Warning | FSD | 23 min |
| Aug 18, 5:46 PM CDT | Severe Thunderstorm Warning | FSD | 29 min |
| Aug 18, 5:57 PM CDT | Severe Thunderstorm Warning | FSD | 33 min |
| Aug 18, 6:18 PM CDT | Mesoscale Discussion | SPC | 27 min |
| Aug 18, 6:26 PM CDT | Severe Thunderstorm Warning | FSD | 34 min |
| Aug 23, 3:43 AM CDT | Heat Advisory | FSD | 11 hr |
| Aug 28, 7:54 AM CDT | Severe Thunderstorm Warning | FSD | 51 min |
| Aug 28, 8:00 AM CDT | Severe Thunderstorm Watch | SPC | 5 hr |
| Aug 28, 10:41 AM CDT | Mesoscale Discussion | SPC | 94 min |
| Aug 31, 6:02 AM CDT | Dense Fog Advisory | FSD | 4 hr |
| Sep 14, 4:02 AM CDT | Frost Advisory | FSD | 28 hr |
| Sep 19, 3:28 PM CDT | Wind Advisory | FSD | 34 hr |
| Oct 4, 3:13 PM CDT | Wind Advisory | FSD | 3 days |
| Nov 4, 3:37 AM CDT | Wind Advisory | FSD | 47 hr |
| Nov 15, 3:26 AM CST | Wind Advisory | FSD | 14 hr |
| Nov 19, 3:43 AM CST | Winter Weather Advisory | FSD | 14 hr |
| Nov 22, 10:28 PM CST | Dense Fog Advisory | FSD | 12 hr |
| Nov 25, 4:30 AM CST | Wind Advisory | FSD | 41 hr |
| Dec 2, 3:28 AM CST | Winter Weather Advisory | FSD | 45 hr |
| Dec 30, 3:15 PM CST | Wind Advisory | FSD | 57 hr |
By product
Every kind of product issued here, grouped by hazard. Each opens the same place narrowed to that product.
| Product | Alerts |
|---|---|
| Severe storms | |
| Severe Thunderstorm Warning | 26 |
| Tornado Warning | 2 |
| Severe Thunderstorm Watch | 7 |
| Tornado Watch | 2 |
| Mesoscale Discussion | 22 |
| Flooding | |
| Flash Flood Warning | 4 |
| River Flood Warning | 17 |
| Flash Flood Watch | 2 |
| River Flood Watch | 2 |
| Winter | |
| Ice Storm Warning | 1 |
| Winter Storm Watch | 1 |
| Winter Weather Advisory | 5 |
| Heat | |
| Excessive Heat Warning | 1 |
| Excessive Heat Watch | 1 |
| Heat Advisory | 4 |
| Cold | |
| Wind Chill Warning | 1 |
| Frost Advisory | 2 |
| Wind Chill Advisory | 5 |
| Wind and dust | |
| High Wind Warning | 1 |
| Wind Advisory | 14 |
| Fog and smoke | |
| Dense Fog Advisory | 6 |
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordForecastThe radar archive20102012
Sources
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.