Alert archive / Michigan / Shiawassee County
Weather alerts in Shiawassee County, Michigan, 2021
105 weather alerts in 2021, from the National Weather Service and the Storm Prediction Center. An alert counts here when it covered this county.
Shiawassee County and its neighbors
Each county as a circle sized by its count in 2021. Tap one for its archive.
- Alerts
- 105
- Warnings
- 22
- Watches
- 11
- Advisories
- 20
- Busiest month
- June26 alerts
- Busiest day
- August 11, 20218 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 Shiawassee County in 2021 had a tornado report inside them.
Shiawassee County, 2021
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 1 | 0 | 100% | 0 | ||
| Severe thunderstorm warnings | 17 | 11 | 35% | 9 | 100% | 35 min |
| Flash flood warnings | 0 | 0 |
Each office's whole area, 2021
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Detroit, MI: tornado warnings | 16 | 5 | 69% | 12 | 50% | 4 min |
| NWS Detroit, MI: severe thunderstorm warnings | 134 | 97 | 28% | 239 | 89% | 26 min |
| NWS Detroit, MI: flash flood warnings | 9 | 0 | 100% | 0 |
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, Eastern Time. Each opens its own page with the text, the map, the radar and the sounding.
| Issued | Product | Office | Lasted |
|---|---|---|---|
| Jan 25, 3:37 PM EST | Winter Weather Advisory | DTX | 31 hr |
| Feb 4, 3:59 AM EST | Winter Weather Advisory | DTX | 39 hr |
| Feb 14, 3:57 PM EST | Winter Weather Advisory | DTX | 18 hr |
| Feb 15, 10:10 AM EST | Winter Weather Advisory | DTX | 26 hr |
| Mar 18, 3:28 AM EDT | Wind Advisory | DTX | 17 hr |
| Mar 24, 2:07 PM EDT | Special Weather Statement | DTX | 53 min |
| Mar 24, 3:17 PM EDT | Special Weather Statement | DTX | 58 min |
| Apr 20, 3:14 AM EDT | Freeze Warning | DTX | 53 hr |
| May 9, 2:53 PM EDT | Frost Advisory | DTX | 17 hr |
| May 10, 2:23 PM EDT | Freeze Warning | DTX | 17 hr |
| May 11, 2:41 PM EDT | Frost Advisory | DTX | 17 hr |
| May 12, 3:28 PM EDT | Frost Advisory | DTX | 16 hr |
| May 29, 2:50 PM EDT | Frost Advisory | DTX | 16 hr |
| Jun 11, 4:26 PM EDT | Mesoscale Discussion | SPC | 94 min |
| Jun 11, 6:02 PM EDT | Special Weather Statement | DTX | 58 min |
| Jun 12, 5:18 PM EDT | Special Weather Statement | DTX | 57 min |
| Jun 12, 5:38 PM EDT | Severe Thunderstorm Warning | DTX | 67 min |
| Jun 12, 6:19 PM EDT | Mesoscale Discussion | SPC | 116 min |
| Jun 12, 6:45 PM EDT | Severe Thunderstorm Warning | DTX | 75 min |
| Jun 12, 10:16 PM EDT | Special Weather Statement | DTX | 59 min |
| Jun 14, 5:30 PM EDT | Special Weather Statement | DTX | 60 min |
| Jun 19, 3:10 PM EDT | Special Weather Statement | DTX | 35 min |
| Jun 20, 6:06 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jun 20, 8:14 PM EDT | Mesoscale Discussion | SPC | 61 min |
| Jun 20, 9:34 PM EDT | Severe Thunderstorm Warning | DTX | 44 min |
| Jun 22, 2:39 PM EDT | Special Weather Statement | DTX | 66 min |
| Jun 26, 4:00 AM EDT | Flood Watch | DTX | 22 hr |
| Jun 26, 1:48 PM EDT | Mesoscale Discussion | SPC | 57 min |
| Jun 26, 3:47 PM EDT | Mesoscale Discussion | SPC | 118 min |
| Jun 26, 4:04 PM EDT | Tornado Watch | SPC | 6 hr |
| Jun 26, 5:32 PM EDT | Severe Thunderstorm Warning | DTX | 58 min |
| Jun 26, 6:05 PM EDT | Tornado Warning | DTX | 55 min |
| Jun 26, 7:08 PM EDT | Mesoscale Discussion | SPC | 67 min |
| Jun 26, 9:23 PM EDT | Mesoscale Discussion | SPC | 67 min |
| Jun 26, 11:48 PM EDT | River Flood Warning | DTX | 15 hr |
| Jun 28, 7:54 PM EDT | Special Weather Statement | DTX | 51 min |
| Jun 29, 12:48 PM EDT | Special Weather Statement | DTX | 57 min |
| Jun 29, 12:54 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jun 29, 1:06 PM EDT | Severe Thunderstorm Warning | DTX | 54 min |
| Jul 7, 1:31 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jul 7, 1:49 PM EDT | Severe Thunderstorm Warning | DTX | 41 min |
| Jul 8, 3:13 AM EDT | Special Weather Statement | DTX | 47 min |
| Jul 13, 3:08 PM EDT | Special Weather Statement | DTX | 67 min |
| Jul 24, 2:21 PM EDT | Mesoscale Discussion | SPC | 114 min |
| Jul 24, 3:16 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jul 24, 4:57 PM EDT | Severe Thunderstorm Warning | DTX | 63 min |
| Jul 24, 6:06 PM EDT | Severe Thunderstorm Warning | DTX | 54 min |
| Jul 24, 6:21 PM EDT | Mesoscale Discussion | SPC | 114 min |
| Jul 24, 7:07 PM EDT | Special Weather Statement | DTX | 53 min |
| Jul 24, 7:19 PM EDT | Areal Flood Advisory | DTX | 3 hr |
| Aug 8, 4:28 AM EDT | Special Weather Statement | DTX | 62 min |
| Aug 10, 8:12 PM EDT | Mesoscale Discussion | SPC | 63 min |
| Aug 10, 10:57 PM EDT | Mesoscale Discussion | SPC | 93 min |
| Aug 10, 11:53 PM EDT | Special Weather Statement | DTX | 52 min |
| Aug 11, 12:02 AM EDT | Severe Thunderstorm Warning | DTX | 58 min |
| Aug 11, 2:12 PM EDT | Mesoscale Discussion | SPC | 93 min |
| Aug 11, 2:32 PM EDT | Severe Thunderstorm Watch | SPC | 4 hr |
| Aug 11, 3:16 PM EDT | Severe Thunderstorm Warning | DTX | 59 min |
| Aug 11, 7:45 PM EDT | Mesoscale Discussion | SPC | 90 min |
| Aug 11, 10:17 PM EDT | Mesoscale Discussion | SPC | 88 min |
| Aug 11, 10:42 PM EDT | Special Weather Statement | DTX | 63 min |
| Aug 12, 1:14 AM EDT | Special Weather Statement | DTX | 46 min |
| Aug 24, 6:19 PM EDT | Mesoscale Discussion | SPC | 116 min |
| Aug 24, 7:08 PM EDT | Special Weather Statement | DTX | 67 min |
| Aug 24, 7:13 PM EDT | Severe Thunderstorm Warning | DTX | 62 min |
| Aug 28, 3:42 AM EDT | Heat Advisory | DTX | 16 hr |
| Aug 28, 6:42 PM EDT | Mesoscale Discussion | SPC | 93 min |
| Aug 28, 7:41 PM EDT | Special Weather Statement | DTX | 79 min |
| Aug 28, 10:00 PM EDT | Severe Thunderstorm Warning | DTX | 20 min |
| Aug 29, 4:07 PM EDT | Special Weather Statement | DTX | 83 min |
| Aug 29, 4:27 PM EDT | Mesoscale Discussion | SPC | 93 min |
| Aug 29, 4:30 PM EDT | Severe Thunderstorm Warning | DTX | 75 min |
| Sep 7, 2:48 PM EDT | Mesoscale Discussion | SPC | 117 min |
| Sep 7, 3:20 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Sep 7, 4:38 PM EDT | Special Weather Statement | DTX | 82 min |
| Sep 7, 5:37 PM EDT | Mesoscale Discussion | SPC | 83 min |
| Sep 7, 5:55 PM EDT | Severe Thunderstorm Warning | DTX | 80 min |
| Sep 7, 7:33 PM EDT | Special Weather Statement | DTX | 57 min |
| Sep 7, 7:36 PM EDT | Severe Thunderstorm Warning | DTX | 17 min |
| Sep 12, 2:43 PM EDT | Mesoscale Discussion | SPC | 92 min |
| Sep 12, 5:22 PM EDT | Severe Thunderstorm Watch | SPC | 4 hr |
| Sep 12, 5:32 PM EDT | Severe Thunderstorm Warning | DTX | 58 min |
| Sep 12, 6:52 PM EDT | Mesoscale Discussion | SPC | 113 min |
| Sep 12, 7:54 PM EDT | Special Weather Statement | DTX | 81 min |
| Sep 13, 12:35 PM EDT | Special Weather Statement | DTX | 55 min |
| Sep 13, 1:19 PM EDT | Severe Thunderstorm Warning | DTX | 56 min |
| Sep 14, 2:12 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Sep 14, 3:08 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Sep 14, 6:04 PM EDT | Mesoscale Discussion | SPC | 86 min |
| Sep 21, 3:08 AM EDT | Flood Watch | DTX | 48 hr |
| Oct 21, 5:31 AM EDT | Special Weather Statement | DTX | 29 min |
| Oct 23, 3:02 PM EDT | Frost Advisory | DTX | 18 hr |
| Nov 10, 2:24 AM EST | Dense Fog Advisory | DTX | 5 hr |
| Nov 21, 7:06 PM EST | Special Weather Statement | DTX | 54 min |
| Nov 27, 3:21 AM EST | Winter Weather Advisory | DTX | 19 hr |
| Nov 28, 3:15 PM EST | Mesoscale Discussion | SPC | 2 hr |
| Nov 29, 5:49 PM EST | Winter Weather Advisory | DTX | 10 hr |
| Dec 6, 3:37 AM EST | Wind Advisory | DTX | 15 hr |
| Dec 9, 3:36 PM EST | High Wind Watch | DTX | 23 hr |
| Dec 10, 2:31 PM EST | High Wind Warning | DTX | 25 hr |
| Dec 10, 2:31 PM EST | Wind Advisory | DTX | 18 hr |
| Dec 11, 1:33 AM EST | Special Weather Statement | DTX | 87 min |
| Dec 11, 3:25 PM EST | Wind Advisory | DTX | 4 hr |
| Dec 15, 3:40 AM EST | Wind Advisory | DTX | 40 hr |
| Dec 26, 10:49 PM EST | Winter Weather Advisory | DTX | 10 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 | 17 |
| Tornado Warning | 1 |
| Severe Thunderstorm Watch | 7 |
| Tornado Watch | 1 |
| Mesoscale Discussion | 25 |
| Special Weather Statement | 27 |
| Flooding | |
| River Flood Warning | 1 |
| Flood Watch | 2 |
| Areal Flood Advisory | 1 |
| Winter | |
| Winter Weather Advisory | 7 |
| Heat | |
| Heat Advisory | 1 |
| Cold | |
| Freeze Warning | 2 |
| Frost Advisory | 5 |
| Wind and dust | |
| High Wind Warning | 1 |
| High Wind Watch | 1 |
| Wind Advisory | 5 |
| 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 archive20202022
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.