Alert archive / South Dakota / Gregory County
Weather alerts in Gregory County, South Dakota, 2009
109 weather alerts in 2009, from the National Weather Service and the Storm Prediction Center. An alert counts here when it covered this county.
Gregory County and its neighbors
Each county as a circle sized by its count in 2009. Tap one for its archive.
- Alerts
- 109
- Warnings
- 28
- Watches
- 19
- Advisories
- 28
- Busiest month
- August20 alerts
- Busiest day
- June 17, 20097 alerts
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
1 of 3 tornado warnings covering Gregory County in 2009 had a tornado report inside them.
Gregory County, 2009
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 3 | 1 | 67% | 0 | ||
| Severe thunderstorm warnings | 16 | 10 | 38% | 12 | 100% | 25 min |
| Flash flood warnings | 1 | 1 | 0% | 1 | 100% | 41 min |
Each office's whole area, 2009
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Sioux Falls, SD: tornado warnings | 49 | 16 | 67% | 23 | 78% | 21 min |
| NWS Sioux Falls, SD: severe thunderstorm warnings | 232 | 172 | 26% | 374 | 81% | 19 min |
| NWS Sioux Falls, SD: flash flood warnings | 25 | 18 | 28% | 34 | 88% | 49 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 3, 8:56 PM CST | Wind Chill Advisory | FSD | 13 hr |
| Jan 11, 2:50 PM CST | Winter Weather Advisory | FSD | 30 hr |
| Jan 11, 2:58 PM CST | Wind Advisory | FSD | 21 hr |
| Jan 12, 10:07 AM CST | High Wind Warning | FSD | 8 hr |
| Jan 12, 10:56 AM CST | Mesoscale Discussion | SPC | 6 hr |
| Jan 13, 3:17 PM CST | Wind Chill Advisory | FSD | 33 hr |
| Feb 9, 2:58 PM CST | Wind Advisory | FSD | 15 hr |
| Feb 25, 11:07 AM CST | Winter Weather Advisory | FSD | 29 hr |
| Feb 27, 4:19 AM CST | Winter Weather Advisory | FSD | 23 hr |
| Feb 27, 11:25 AM CST | Mesoscale Discussion | SPC | 4 hr |
| Feb 27, 12:14 PM CST | Winter Storm Warning | FSD | 10 hr |
| Mar 6, 3:39 PM CST | Winter Weather Advisory | FSD | 44 hr |
| Mar 9, 4:05 PM CDT | Winter Weather Advisory | FSD | 12 hr |
| Mar 10, 2:51 PM CDT | Wind Chill Advisory | FSD | 21 hr |
| Mar 22, 3:44 AM CDT | Wind Advisory | FSD | 44 hr |
| Mar 23, 10:13 AM CDT | Mesoscale Discussion | SPC | 2 hr |
| Mar 23, 12:16 PM CDT | Tornado Watch | SPC | 4 hr |
| Mar 23, 3:11 PM CDT | Mesoscale Discussion | SPC | 94 min |
| Mar 23, 3:34 PM CDT | Severe Thunderstorm Warning | FSD | 41 min |
| Mar 23, 3:50 PM CDT | Tornado Watch | SPC | 6 hr |
| Mar 23, 4:12 PM CDT | Severe Thunderstorm Warning | FSD | 38 min |
| Mar 24, 3:25 AM CDT | Wind Advisory | FSD | 21 hr |
| Mar 24, 10:45 AM CDT | Winter Weather Advisory | FSD | 8 hr |
| Mar 29, 4:02 PM CDT | Winter Storm Warning | FSD | 12 hr |
| Mar 30, 4:08 AM CDT | Blizzard Warning | FSD | 39 hr |
| Mar 30, 3:20 PM CDT | Mesoscale Discussion | SPC | 6 hr |
| Mar 30, 7:59 PM CDT | Mesoscale Discussion | SPC | 4 hr |
| Mar 31, 1:22 AM CDT | Mesoscale Discussion | SPC | 4 hr |
| Apr 2, 3:24 PM CDT | Winter Storm Watch | FSD | 30 hr |
| Apr 3, 10:40 AM CDT | Blizzard Warning | FSD | 41 hr |
| Apr 4, 3:20 PM CDT | Mesoscale Discussion | SPC | 2 hr |
| Apr 15, 11:05 AM CDT | Wind Advisory | FSD | 8 hr |
| Apr 29, 9:27 PM CDT | Mesoscale Discussion | SPC | 93 min |
| May 4, 6:21 PM CDT | Mesoscale Discussion | SPC | 84 min |
| May 12, 3:49 PM CDT | High Wind Watch | FSD | 12 hr |
| May 12, 3:49 PM CDT | Wind Advisory | FSD | 30 hr |
| May 12, 7:08 PM CDT | Severe Thunderstorm Watch | SPC | 7 hr |
| May 12, 8:42 PM CDT | Mesoscale Discussion | SPC | 93 min |
| May 19, 3:31 AM CDT | Wind Advisory | FSD | 17 hr |
| Jun 7, 11:16 AM CDT | Mesoscale Discussion | SPC | 119 min |
| Jun 15, 4:08 PM CDT | Mesoscale Discussion | SPC | 67 min |
| Jun 16, 4:16 PM CDT | Tornado Watch | SPC | 7 hr |
| Jun 17, 5:02 PM CDT | Mesoscale Discussion | SPC | 88 min |
| Jun 17, 5:26 PM CDT | Mesoscale Discussion | SPC | 94 min |
| Jun 17, 5:43 PM CDT | Severe Thunderstorm Warning | FSD | 47 min |
| Jun 17, 5:43 PM CDT | Mesoscale Discussion | SPC | 92 min |
| Jun 17, 5:54 PM CDT | Tornado Warning | FSD | 36 min |
| Jun 17, 6:21 PM CDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jun 17, 6:31 PM CDT | Severe Thunderstorm Warning | FSD | 44 min |
| Jun 18, 6:52 PM CDT | Mesoscale Discussion | SPC | 113 min |
| Jun 23, 4:43 AM CDT | Mesoscale Discussion | SPC | 92 min |
| Jun 23, 7:24 AM CDT | Mesoscale Discussion | SPC | 96 min |
| Jun 26, 6:24 PM CDT | Tornado Watch | SPC | 4 hr |
| Jun 26, 8:55 PM CDT | Mesoscale Discussion | SPC | 95 min |
| Jun 26, 9:22 PM CDT | Severe Thunderstorm Warning | FSD | 38 min |
| Jun 26, 9:59 PM CDT | Severe Thunderstorm Warning | FSD | 46 min |
| Jul 7, 2:13 PM CDT | Severe Thunderstorm Watch | SPC | 8 hr |
| Jul 7, 6:33 PM CDT | Mesoscale Discussion | SPC | 27 min |
| Jul 8, 9:58 PM CDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jul 8, 11:27 PM CDT | Mesoscale Discussion | SPC | 93 min |
| Jul 9, 2:46 AM CDT | Severe Thunderstorm Warning | FSD | 33 min |
| Jul 9, 3:07 AM CDT | Mesoscale Discussion | SPC | 83 min |
| Jul 13, 5:52 PM CDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jul 13, 11:24 PM CDT | Mesoscale Discussion | SPC | 66 min |
| Jul 16, 3:01 AM CDT | Severe Thunderstorm Warning | FSD | 44 min |
| Jul 16, 3:52 AM CDT | Severe Thunderstorm Warning | FSD | 17 min |
| Jul 31, 1:35 PM CDT | Mesoscale Discussion | SPC | 115 min |
| Aug 3, 6:58 PM CDT | Mesoscale Discussion | SPC | 2 hr |
| Aug 3, 8:02 PM CDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Aug 3, 9:26 PM CDT | Severe Thunderstorm Warning | FSD | 49 min |
| Aug 3, 10:11 PM CDT | Severe Thunderstorm Warning | FSD | 22 min |
| Aug 3, 10:40 PM CDT | Mesoscale Discussion | SPC | 2 hr |
| Aug 3, 11:39 PM CDT | Severe Thunderstorm Warning | FSD | 51 min |
| Aug 7, 8:57 PM CDT | Severe Thunderstorm Watch | SPC | 5 hr |
| Aug 8, 10:52 AM CDT | Mesoscale Discussion | SPC | 23 min |
| Aug 8, 11:09 AM CDT | Severe Thunderstorm Warning | FSD | 36 min |
| Aug 8, 11:15 AM CDT | Severe Thunderstorm Watch | SPC | 4 hr |
| Aug 8, 1:55 PM CDT | Severe Thunderstorm Warning | FSD | 50 min |
| Aug 8, 1:57 PM CDT | Severe Thunderstorm Warning | FSD | 48 min |
| Aug 8, 2:17 PM CDT | Mesoscale Discussion | SPC | 58 min |
| Aug 12, 9:17 PM CDT | Severe Thunderstorm Warning | FSD | 58 min |
| Aug 15, 6:52 PM CDT | Mesoscale Discussion | SPC | 53 min |
| Aug 15, 8:05 PM CDT | Severe Thunderstorm Watch | SPC | 5 hr |
| Aug 15, 8:07 PM CDT | Flash Flood Warning | FSD | 3 hr |
| Aug 18, 3:35 PM CDT | Mesoscale Discussion | SPC | 115 min |
| Aug 18, 6:10 PM CDT | Severe Thunderstorm Watch | SPC | 5 hr |
| Aug 18, 9:41 PM CDT | Mesoscale Discussion | SPC | 64 min |
| Sep 2, 3:53 PM CDT | Tornado Warning | FSD | 22 min |
| Sep 2, 4:11 PM CDT | Tornado Warning | FSD | 49 min |
| Sep 8, 2:53 PM CDT | Severe Thunderstorm Watch | SPC | 8 hr |
| Sep 8, 7:10 PM CDT | Mesoscale Discussion | SPC | 2 hr |
| Sep 26, 2:26 PM CDT | Wind Advisory | FSD | 30 hr |
| Sep 28, 3:20 PM CDT | Frost Advisory | FSD | 18 hr |
| Sep 30, 3:54 PM CDT | Wind Advisory | FSD | 23 hr |
| Oct 2, 4:14 AM CDT | Wind Advisory | FSD | 11 hr |
| Oct 8, 3:43 AM CDT | Freeze Warning | FSD | 28 hr |
| Oct 10, 3:16 PM CDT | Winter Storm Watch | FSD | 24 hr |
| Oct 11, 4:01 AM CDT | Winter Weather Advisory | FSD | 30 hr |
| Oct 29, 11:51 AM CDT | Winter Weather Advisory | FSD | 19 hr |
| Dec 1, 3:00 AM CST | Wind Advisory | FSD | 15 hr |
| Dec 7, 3:39 AM CST | Winter Weather Advisory | FSD | 49 hr |
| Dec 9, 4:10 AM CST | Wind Chill Advisory | FSD | 30 hr |
| Dec 21, 2:02 PM CST | Winter Storm Watch | FSD | 24 hr |
| Dec 21, 9:48 PM CST | Dense Fog Advisory | FSD | 4 hr |
| Dec 22, 4:30 AM CST | Winter Storm Warning | FSD | 4 days |
| Dec 23, 4:48 AM CST | Winter Weather Advisory | FSD | 13 hr |
| Dec 24, 3:31 PM CST | Blizzard Warning | FSD | 44 hr |
| Dec 25, 7:21 AM CST | Mesoscale Discussion | SPC | 5 hr |
| Dec 26, 3:56 AM CST | Winter Weather Advisory | FSD | 20 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 | 3 |
| Severe Thunderstorm Watch | 11 |
| Tornado Watch | 4 |
| Mesoscale Discussion | 34 |
| Flooding | |
| Flash Flood Warning | 1 |
| Winter | |
| Blizzard Warning | 3 |
| Winter Storm Warning | 3 |
| Winter Storm Watch | 3 |
| Winter Weather Advisory | 11 |
| Cold | |
| Freeze Warning | 1 |
| Frost Advisory | 1 |
| Wind Chill Advisory | 4 |
| Wind and dust | |
| High Wind Warning | 1 |
| High Wind Watch | 1 |
| Wind Advisory | 11 |
| Fog and smoke | |
| Dense Fog Advisory | 1 |
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordForecastThe radar archive20082010
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.