Alert archive / South Dakota / Union County
Weather alerts in Union County, South Dakota, 2017
84 weather alerts in 2017, 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 2017. Tap one for its archive.
- Alerts
- 84
- Warnings
- 31
- Watches
- 14
- Advisories
- 21
- Busiest month
- June19 alerts
- Busiest day
- June 29, 201710 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 2017 had a tornado report inside them.
Union County, 2017
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 1 | 0 | 100% | 0 | ||
| Severe thunderstorm warnings | 16 | 12 | 25% | 5 | 80% | 24 min |
| Flash flood warnings | 3 | 0 | 100% | 0 |
Each office's whole area, 2017
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Sioux Falls, SD: tornado warnings | 36 | 6 | 83% | 13 | 62% | 16 min |
| NWS Sioux Falls, SD: severe thunderstorm warnings | 270 | 214 | 21% | 354 | 87% | 19 min |
| NWS Sioux Falls, SD: flash flood warnings | 7 | 2 | 71% | 4 | 75% | 68 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, 3:47 AM CST | Winter Weather Advisory | FSD | 35 hr |
| Jan 12, 3:35 PM CST | Winter Storm Watch | FSD | 71 hr |
| Jan 15, 4:41 AM CST | Winter Weather Advisory | FSD | 43 hr |
| Jan 19, 3:28 PM CST | Dense Fog Advisory | FSD | 46 hr |
| Jan 22, 2:33 PM CST | Winter Storm Watch | FSD | 24 hr |
| Jan 23, 2:59 PM CST | Winter Storm Warning | FSD | 51 hr |
| Jan 30, 3:25 AM CST | Wind Advisory | FSD | 18 hr |
| Feb 21, 3:59 PM CST | Winter Storm Watch | FSD | 36 hr |
| Feb 22, 3:22 PM CST | Blizzard Watch | FSD | 20 hr |
| Feb 23, 4:14 AM CST | Blizzard Warning | FSD | 37 hr |
| Feb 23, 6:05 PM CST | Mesoscale Discussion | SPC | 6 hr |
| Feb 23, 11:54 PM CST | Mesoscale Discussion | SPC | 6 hr |
| Mar 5, 4:04 PM CST | Wind Advisory | FSD | 68 hr |
| Mar 6, 4:27 PM CST | Wind Advisory | FSD | 44 hr |
| Mar 23, 10:16 AM CDT | Mesoscale Discussion | SPC | 89 min |
| Apr 3, 1:52 AM CDT | Dense Fog Advisory | FSD | 10 hr |
| Apr 9, 3:16 PM CDT | Mesoscale Discussion | SPC | 119 min |
| Apr 15, 4:01 PM CDT | Mesoscale Discussion | SPC | 119 min |
| Apr 15, 6:22 PM CDT | Mesoscale Discussion | SPC | 83 min |
| Apr 15, 7:00 PM CDT | Severe Thunderstorm Warning | FSD | 45 min |
| May 2, 9:22 AM CDT | River Flood Warning | FSD | 3 days |
| May 15, 11:54 PM CDT | Severe Thunderstorm Watch | SPC | 3 hr |
| May 16, 2:13 AM CDT | Mesoscale Discussion | SPC | 92 min |
| May 16, 7:31 PM CDT | Mesoscale Discussion | SPC | 59 min |
| May 17, 11:16 AM CDT | River Flood Warning | FSD | 5 days |
| May 17, 11:16 AM CDT | River Flood Warning | FSD | 6 days |
| May 20, 9:19 PM CDT | River Flood Warning | FSD | 4 days |
| May 23, 7:55 AM CDT | River Flood Warning | FSD | 53 hr |
| Jun 7, 5:27 PM CDT | Severe Thunderstorm Warning | FSD | 21 min |
| Jun 12, 12:08 PM CDT | Severe Thunderstorm Warning | FSD | 38 min |
| Jun 13, 3:46 PM CDT | Mesoscale Discussion | SPC | 2 hr |
| Jun 13, 7:01 PM CDT | Tornado Watch | SPC | 6 hr |
| Jun 13, 8:34 PM CDT | Mesoscale Discussion | SPC | 56 min |
| Jun 13, 9:10 PM CDT | Severe Thunderstorm Warning | FSD | 50 min |
| Jun 13, 9:16 PM CDT | Severe Thunderstorm Warning | FSD | 44 min |
| Jun 16, 3:53 PM CDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jun 27, 7:35 PM CDT | Severe Thunderstorm Watch | SPC | 5 hr |
| Jun 29, 2:26 PM CDT | Mesoscale Discussion | SPC | 94 min |
| Jun 29, 3:22 PM CDT | Severe Thunderstorm Warning | FSD | 53 min |
| Jun 29, 3:42 PM CDT | Severe Thunderstorm Watch | SPC | 8 hr |
| Jun 29, 3:48 PM CDT | Severe Thunderstorm Warning | FSD | 42 min |
| Jun 29, 4:26 PM CDT | Severe Thunderstorm Warning | FSD | 49 min |
| Jun 29, 4:47 PM CDT | Flash Flood Warning | FSD | 3 hr |
| Jun 29, 6:03 PM CDT | Severe Thunderstorm Warning | FSD | 27 min |
| Jun 29, 6:08 PM CDT | Mesoscale Discussion | SPC | 67 min |
| Jun 29, 6:12 PM CDT | Tornado Warning | FSD | 18 min |
| Jun 29, 6:27 PM CDT | Severe Thunderstorm Warning | FSD | 33 min |
| Jul 11, 4:26 AM CDT | Heat Advisory | FSD | 15 hr |
| Jul 18, 3:07 PM CDT | Heat Advisory | FSD | 29 hr |
| Jul 19, 4:52 PM CDT | Severe Thunderstorm Watch | SPC | 6 hr |
| Jul 19, 7:06 PM CDT | Mesoscale Discussion | SPC | 84 min |
| Jul 20, 3:25 PM CDT | Heat Advisory | FSD | 29 hr |
| Jul 22, 3:26 AM CDT | Severe Thunderstorm Warning | FSD | 26 min |
| Aug 13, 4:00 PM CDT | Severe Thunderstorm Watch | SPC | 11 hr |
| Aug 13, 7:38 PM CDT | Mesoscale Discussion | SPC | 97 min |
| Aug 19, 9:30 PM CDT | Severe Thunderstorm Warning | FSD | 29 min |
| Aug 19, 9:54 PM CDT | Severe Thunderstorm Warning | FSD | 36 min |
| Aug 21, 11:12 AM CDT | Mesoscale Discussion | SPC | 93 min |
| Aug 21, 11:33 AM CDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Aug 21, 1:40 PM CDT | Severe Thunderstorm Warning | FSD | 50 min |
| Aug 21, 2:35 PM CDT | Mesoscale Discussion | SPC | 85 min |
| Aug 25, 12:07 PM CDT | Flash Flood Warning | FSD | 113 min |
| Sep 15, 5:48 PM CDT | Mesoscale Discussion | SPC | 2 hr |
| Sep 22, 10:35 AM CDT | Heat Advisory | FSD | 7 hr |
| Sep 22, 3:57 PM CDT | Mesoscale Discussion | SPC | 2 hr |
| Oct 2, 2:22 PM CDT | Flash Flood Watch | FSD | 13 hr |
| Oct 4, 9:41 AM CDT | River Flood Warning | FSD | 9 days |
| Oct 4, 9:41 AM CDT | River Flood Warning | FSD | 8 days |
| Oct 6, 6:51 AM CDT | Severe Thunderstorm Warning | FSD | 24 min |
| Oct 6, 7:14 AM CDT | Severe Thunderstorm Warning | FSD | 46 min |
| Oct 6, 10:15 AM CDT | Flash Flood Warning | FSD | 3 hr |
| Oct 6, 3:56 PM CDT | Flash Flood Watch | FSD | 11 hr |
| Oct 9, 3:06 AM CDT | Frost Advisory | FSD | 30 hr |
| Oct 10, 2:22 PM CDT | Freeze Warning | FSD | 20 hr |
| Oct 22, 3:21 PM CDT | Wind Advisory | FSD | 51 hr |
| Oct 25, 3:05 PM CDT | Wind Advisory | FSD | 51 hr |
| Dec 3, 3:59 PM CST | Wind Advisory | FSD | 32 hr |
| Dec 11, 2:59 AM CST | Wind Advisory | FSD | 15 hr |
| Dec 12, 2:43 PM CST | Wind Advisory | FSD | 27 hr |
| Dec 21, 9:48 AM CST | Winter Weather Advisory | FSD | 13 hr |
| Dec 25, 4:29 AM CST | Wind Chill Advisory | FSD | 32 hr |
| Dec 26, 2:31 PM CST | Wind Chill Advisory | FSD | 20 hr |
| Dec 29, 3:50 PM CST | Wind Chill Advisory | FSD | 32 hr |
| Dec 30, 2:59 AM CST | Wind Chill Warning | 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 | 16 |
| Tornado Warning | 1 |
| Severe Thunderstorm Watch | 7 |
| Tornado Watch | 1 |
| Mesoscale Discussion | 18 |
| Flooding | |
| Flash Flood Warning | 3 |
| River Flood Warning | 7 |
| Flash Flood Watch | 2 |
| Winter | |
| Blizzard Warning | 1 |
| Winter Storm Warning | 1 |
| Blizzard Watch | 1 |
| Winter Storm Watch | 3 |
| Winter Weather Advisory | 3 |
| Heat | |
| Heat Advisory | 4 |
| Cold | |
| Freeze Warning | 1 |
| Wind Chill Warning | 1 |
| Frost Advisory | 1 |
| Wind Chill Advisory | 3 |
| Wind and dust | |
| Wind Advisory | 8 |
| Fog and smoke | |
| Dense Fog Advisory | 2 |
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordForecastThe radar archive20162018
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.