Alert archive / South Dakota / Union County
Weather alerts in Union County, South Dakota, 2018
133 weather alerts in 2018, 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 2018. Tap one for its archive.
- Alerts
- 133
- Warnings
- 62
- Watches
- 18
- Advisories
- 35
- Busiest month
- June33 alerts
- Busiest day
- June 25, 20189 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 1 tornado warnings covering Union County in 2018 had a tornado report inside them.
Union County, 2018
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 1 | 0 | 100% | 0 | ||
| Severe thunderstorm warnings | 5 | 3 | 40% | 1 | 0% | |
| Flash flood warnings | 6 | 5 | 17% | 1 | 100% | 175 min |
Each office's whole area, 2018
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Sioux Falls, SD: tornado warnings | 12 | 3 | 75% | 10 | 40% | 9 min |
| NWS Sioux Falls, SD: severe thunderstorm warnings | 165 | 77 | 53% | 157 | 81% | 19 min |
| NWS Sioux Falls, SD: flash flood warnings | 43 | 31 | 28% | 66 | 82% | 104 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, 12:01 PM CST | Wind Chill Advisory | FSD | 22 hr |
| Jan 9, 3:46 AM CST | Winter Storm Watch | FSD | 35 hr |
| Jan 10, 3:07 AM CST | Winter Weather Advisory | FSD | 38 hr |
| Jan 14, 3:20 AM CST | Wind Chill Advisory | FSD | 56 hr |
| Jan 19, 4:20 AM CST | Winter Storm Watch | FSD | 47 hr |
| Jan 20, 2:54 PM CST | Winter Storm Warning | FSD | 54 hr |
| Jan 21, 3:41 AM CST | Blizzard Warning | FSD | 43 hr |
| Jan 22, 2:02 AM CST | Mesoscale Discussion | SPC | 6 hr |
| Jan 22, 9:20 AM CST | Mesoscale Discussion | SPC | 6 hr |
| Jan 24, 1:03 AM CST | Dense Fog Advisory | FSD | 13 hr |
| Jan 24, 2:32 PM CST | Dense Fog Advisory | FSD | 23 hr |
| Feb 4, 3:12 PM CST | Winter Weather Advisory | FSD | 21 hr |
| Feb 7, 3:41 PM CST | Winter Weather Advisory | FSD | 35 hr |
| Feb 18, 2:53 AM CST | Wind Advisory | FSD | 11 hr |
| Feb 18, 3:48 AM CST | Winter Weather Advisory | FSD | 54 hr |
| Feb 21, 2:59 PM CST | Winter Weather Advisory | FSD | 33 hr |
| Feb 22, 3:56 PM CST | Winter Storm Watch | FSD | 23 hr |
| Feb 23, 3:00 PM CST | Winter Weather Advisory | FSD | 27 hr |
| Feb 23, 10:16 PM CST | Dense Fog Advisory | FSD | 11 hr |
| Mar 4, 4:09 AM CST | Blizzard Warning | FSD | 59 hr |
| Mar 4, 2:25 PM CST | Winter Weather Advisory | FSD | 49 hr |
| Mar 6, 4:07 PM CST | River Flood Warning | FSD | 61 hr |
| Mar 8, 8:47 AM CST | River Flood Warning | FSD | 45 hr |
| Mar 15, 3:48 AM CDT | Winter Weather Advisory | FSD | 45 hr |
| Mar 23, 9:37 AM CDT | River Flood Warning | FSD | 13 days |
| Mar 25, 9:44 AM CDT | River Flood Warning | FSD | 4 days |
| Mar 29, 8:26 AM CDT | River Flood Warning | FSD | 6 days |
| Mar 30, 3:05 PM CDT | Wind Advisory | FSD | 22 hr |
| Apr 2, 2:20 PM CDT | Winter Weather Advisory | FSD | 31 hr |
| Apr 7, 2:53 PM CDT | Winter Weather Advisory | FSD | 34 hr |
| Apr 11, 3:37 PM CDT | Winter Storm Watch | FSD | 24 hr |
| Apr 12, 3:45 PM CDT | Blizzard Warning | FSD | 60 hr |
| Apr 13, 9:41 AM CDT | River Flood Warning | FSD | 59 hr |
| Apr 13, 9:41 AM CDT | River Flood Warning | FSD | 3 days |
| Apr 14, 10:06 AM CDT | Mesoscale Discussion | SPC | 6 hr |
| Apr 15, 3:27 AM CDT | Winter Weather Advisory | FSD | 13 hr |
| Apr 16, 3:21 AM CDT | Winter Storm Watch | FSD | 24 hr |
| Apr 17, 3:33 AM CDT | Winter Weather Advisory | FSD | 38 hr |
| Apr 17, 9:50 AM CDT | River Flood Warning | FSD | 18 days |
| Apr 17, 9:50 AM CDT | River Flood Warning | FSD | 19 days |
| Apr 29, 3:41 AM CDT | Wind Advisory | FSD | 16 hr |
| Apr 30, 3:31 AM CDT | Wind Advisory | FSD | 15 hr |
| May 10, 10:08 AM CDT | River Flood Warning | FSD | 5 days |
| May 10, 10:08 AM CDT | River Flood Warning | FSD | 7 days |
| May 13, 7:39 PM CDT | River Flood Warning | FSD | 4 days |
| May 15, 1:41 AM CDT | Dense Fog Advisory | FSD | 7 hr |
| May 27, 3:28 AM CDT | Heat Advisory | FSD | 16 hr |
| Jun 1, 10:05 PM CDT | Severe Thunderstorm Watch | SPC | 5 hr |
| Jun 8, 11:51 PM CDT | Mesoscale Discussion | SPC | 84 min |
| Jun 11, 2:38 PM CDT | Mesoscale Discussion | SPC | 2 hr |
| Jun 11, 3:42 PM CDT | Tornado Watch | SPC | 6 hr |
| Jun 13, 11:56 PM CDT | Mesoscale Discussion | SPC | 3 hr |
| Jun 14, 2:50 PM CDT | Heat Advisory | FSD | 3 days |
| Jun 17, 3:52 PM CDT | Mesoscale Discussion | SPC | 53 min |
| Jun 18, 1:34 PM CDT | Mesoscale Discussion | SPC | 56 min |
| Jun 18, 3:05 PM CDT | Severe Thunderstorm Watch | SPC | 6 hr |
| Jun 18, 5:46 PM CDT | Mesoscale Discussion | SPC | 119 min |
| Jun 18, 9:48 PM CDT | Areal Flood Warning | FSD | 12 hr |
| Jun 20, 3:16 AM CDT | Flash Flood Watch | FSD | 28 hr |
| Jun 20, 9:10 PM CDT | River Flood Warning | FSD | 20 days |
| Jun 20, 9:10 PM CDT | River Flood Warning | FSD | 21 days |
| Jun 21, 4:33 AM CDT | Areal Flood Warning | FSD | 48 hr |
| Jun 21, 1:07 PM CDT | Areal Flood Warning | FSD | 24 hr |
| Jun 21, 11:16 PM CDT | River Flood Warning | FSD | 20 days |
| Jun 21, 11:16 PM CDT | River Flood Warning | FSD | 6 days |
| Jun 23, 5:27 AM CDT | Areal Flood Warning | FSD | 48 hr |
| Jun 24, 7:53 PM CDT | Flash Flood Warning | FSD | 3 hr |
| Jun 24, 9:05 PM CDT | Flash Flood Warning | FSD | 3 hr |
| Jun 24, 9:52 PM CDT | Flash Flood Watch | FSD | 25 hr |
| Jun 24, 10:41 PM CDT | Flash Flood Warning | FSD | 4 hr |
| Jun 24, 11:13 PM CDT | Flash Flood Warning | FSD | 4 hr |
| Jun 25, 2:05 AM CDT | River Flood Warning | FSD | 7 days |
| Jun 25, 2:46 AM CDT | Areal Flood Warning | FSD | 12 hr |
| Jun 25, 5:29 AM CDT | Areal Flood Warning | FSD | 12 hr |
| Jun 25, 4:48 PM CDT | River Flood Warning | FSD | 4 days |
| Jun 26, 2:24 AM CDT | Areal Flood Warning | FSD | 12 hr |
| Jun 26, 5:21 AM CDT | River Flood Warning | FSD | 12 hr |
| Jun 26, 2:28 PM CDT | Areal Flood Warning | FSD | 24 hr |
| Jun 28, 3:17 AM CDT | Heat Advisory | FSD | 41 hr |
| Jun 30, 12:40 PM CDT | Mesoscale Discussion | SPC | 3 hr |
| Jul 4, 4:16 AM CDT | Heat Advisory | FSD | 16 hr |
| Jul 4, 2:01 PM CDT | Mesoscale Discussion | SPC | 119 min |
| Jul 4, 5:35 PM CDT | Mesoscale Discussion | SPC | 115 min |
| Jul 10, 2:39 PM CDT | Heat Advisory | FSD | 53 hr |
| Jul 12, 4:47 AM CDT | Flash Flood Watch | FSD | 26 hr |
| Jul 12, 2:47 PM CDT | Mesoscale Discussion | SPC | 2 hr |
| Jul 12, 3:24 PM CDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jul 13, 9:50 AM CDT | River Flood Warning | FSD | 5 days |
| Jul 13, 9:50 AM CDT | River Flood Warning | FSD | 5 days |
| Jul 15, 12:39 AM CDT | River Flood Warning | FSD | 70 hr |
| Jul 15, 6:18 AM CDT | Dense Fog Advisory | FSD | 3 hr |
| Aug 5, 1:00 AM CDT | Severe Thunderstorm Watch | SPC | 4 hr |
| Aug 5, 2:25 AM CDT | Severe Thunderstorm Warning | FSD | 50 min |
| Aug 5, 3:06 AM CDT | Severe Thunderstorm Warning | FSD | 39 min |
| Aug 26, 9:53 AM CDT | Mesoscale Discussion | SPC | 2 hr |
| Aug 27, 11:49 AM CDT | Mesoscale Discussion | SPC | 116 min |
| Aug 27, 2:24 PM CDT | Severe Thunderstorm Warning | FSD | 36 min |
| Aug 27, 2:51 PM CDT | Severe Thunderstorm Warning | FSD | 39 min |
| Aug 28, 3:12 AM CDT | Mesoscale Discussion | SPC | 3 hr |
| Sep 5, 3:21 AM CDT | River Flood Warning | FSD | 8 hr |
| Sep 19, 2:40 AM CDT | Mesoscale Discussion | SPC | 3 hr |
| Sep 19, 10:31 AM CDT | Flash Flood Watch | FSD | 26 hr |
| Sep 20, 4:35 AM CDT | Flash Flood Warning | FSD | 5 hr |
| Sep 20, 6:49 AM CDT | River Flood Warning | FSD | 10 days |
| Sep 20, 6:49 AM CDT | River Flood Warning | FSD | 12 days |
| Sep 20, 9:30 AM CDT | Flash Flood Warning | FSD | 3 hr |
| Sep 20, 12:39 PM CDT | Areal Flood Warning | FSD | 12 hr |
| Sep 20, 3:11 PM CDT | Severe Thunderstorm Watch | SPC | 8 hr |
| Sep 20, 3:59 PM CDT | Severe Thunderstorm Warning | FSD | 46 min |
| Sep 20, 4:17 PM CDT | Tornado Warning | FSD | 28 min |
| Sep 21, 12:31 AM CDT | Areal Flood Warning | FSD | 24 hr |
| Sep 21, 2:14 AM CDT | River Flood Warning | FSD | 67 hr |
| Sep 21, 8:38 AM CDT | River Flood Warning | FSD | 11 days |
| Sep 22, 12:35 AM CDT | Areal Flood Warning | FSD | 24 hr |
| Sep 23, 8:34 PM CDT | River Flood Warning | FSD | 5 days |
| Oct 3, 10:18 AM CDT | Wind Advisory | FSD | 11 hr |
| Oct 7, 3:37 PM CDT | Flood Watch | FSD | 54 hr |
| Oct 10, 9:46 AM CDT | River Flood Warning | FSD | 9 days |
| Oct 10, 9:46 AM CDT | River Flood Warning | FSD | 11 days |
| Oct 10, 3:18 PM CDT | Freeze Warning | FSD | 18 hr |
| Oct 11, 4:38 AM CDT | River Flood Warning | FSD | 10 days |
| Nov 2, 8:15 PM CDT | River Flood Warning | FSD | 5 days |
| Nov 2, 8:15 PM CDT | River Flood Warning | FSD | 24 hr |
| Nov 28, 4:05 AM CST | Winter Weather Advisory | FSD | 17 hr |
| Nov 28, 2:25 PM CST | Winter Storm Watch | FSD | 48 hr |
| Nov 29, 2:45 PM CST | Winter Storm Warning | FSD | 69 hr |
| Nov 29, 9:09 PM CST | Dense Fog Advisory | FSD | 15 hr |
| Dec 1, 10:46 AM CST | Mesoscale Discussion | SPC | 3 hr |
| Dec 8, 2:00 AM CST | Dense Fog Advisory | FSD | 10 hr |
| Dec 14, 1:06 AM CST | Dense Fog Advisory | FSD | 7 hr |
| Dec 26, 3:25 AM CST | Winter Weather Advisory | FSD | 57 hr |
| Dec 26, 12:05 PM CST | Flood Watch | FSD | 31 hr |
| Dec 30, 3:33 PM CST | Winter Weather Advisory | FSD | 29 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 | 5 |
| Tornado Warning | 1 |
| Severe Thunderstorm Watch | 5 |
| Tornado Watch | 1 |
| Mesoscale Discussion | 18 |
| Flooding | |
| Areal Flood Warning | 11 |
| Flash Flood Warning | 6 |
| River Flood Warning | 33 |
| Flash Flood Watch | 4 |
| Flood Watch | 2 |
| Winter | |
| Blizzard Warning | 3 |
| Winter Storm Warning | 2 |
| Winter Storm Watch | 6 |
| Winter Weather Advisory | 15 |
| Heat | |
| Heat Advisory | 5 |
| Cold | |
| Freeze Warning | 1 |
| Wind Chill Advisory | 2 |
| Wind and dust | |
| Wind Advisory | 5 |
| Fog and smoke | |
| Dense Fog Advisory | 8 |
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordForecastThe radar archive20172019
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.