Alert archive / Colorado / Grand County
Weather alerts in Grand County, Colorado, 2020
85 weather alerts in 2020, from the National Weather Service and the Storm Prediction Center. An alert counts here when it covered this county.
Grand County and its neighbors
Each county as a circle sized by its count in 2020. Tap one for its archive.
- Alerts
- 85
- Warnings
- 36
- Watches
- 17
- Advisories
- 24
- Busiest month
- October14 alerts
- Busiest day
- June 6, 20204 alerts
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
Grand County, 2020
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 0 | 0 | ||||
| Severe thunderstorm warnings | 5 | 4 | 20% | 9 | 89% | 26 min |
| Flash flood warnings | 0 | 0 |
Each office's whole area, 2020
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Denver/Boulder, CO: tornado warnings | 5 | 2 | 60% | 25 | 16% | 13 min |
| NWS Denver/Boulder, CO: severe thunderstorm warnings | 220 | 86 | 61% | 308 | 72% | 26 min |
| NWS Denver/Boulder, CO: flash flood warnings | 5 | 1 | 80% | 1 | 100% | 29 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, Mountain Time. Each opens its own page with the text, the map, the radar and the sounding.
| Issued | Product | Office | Lasted |
|---|---|---|---|
| Jan 5, 1:00 PM MST | Winter Weather Advisory | BOU | 26 hr |
| Jan 10, 2:41 PM MST | Winter Weather Advisory | BOU | 39 hr |
| Jan 16, 2:01 PM MST | Winter Weather Advisory | BOU | 30 hr |
| Jan 27, 4:31 AM MST | Winter Weather Advisory | BOU | 19 hr |
| Feb 1, 3:25 PM MST | Winter Storm Watch | BOU | 24 hr |
| Feb 2, 3:45 PM MST | Winter Storm Warning | BOU | 36 hr |
| Feb 2, 3:45 PM MST | Winter Weather Advisory | BOU | 42 hr |
| Feb 4, 2:51 PM MST | Winter Storm Watch | BOU | 11 hr |
| Feb 5, 2:07 AM MST | Winter Storm Warning | BOU | 70 hr |
| Feb 6, 3:15 AM MST | Winter Weather Advisory | BOU | 45 hr |
| Feb 8, 3:26 PM MST | Winter Weather Advisory | BOU | 33 hr |
| Feb 14, 4:06 PM MST | Winter Storm Watch | BOU | 22 hr |
| Feb 15, 4:07 AM MST | Winter Storm Warning | BOU | 52 hr |
| Feb 15, 1:47 PM MST | Winter Weather Advisory | BOU | 42 hr |
| Feb 22, 3:26 AM MST | Winter Weather Advisory | BOU | 35 hr |
| Feb 24, 3:42 AM MST | Winter Weather Advisory | BOU | 37 hr |
| Feb 24, 8:12 AM MST | Snow Squall Warning | BOU | 63 min |
| Mar 1, 9:18 AM MST | Winter Weather Advisory | BOU | 18 hr |
| Mar 17, 1:15 PM MDT | Winter Storm Watch | BOU | 24 hr |
| Mar 18, 5:02 AM MDT | Winter Storm Warning | BOU | 43 hr |
| Mar 18, 5:02 AM MDT | Winter Weather Advisory | BOU | 49 hr |
| Mar 26, 2:48 PM MDT | Winter Weather Advisory | BOU | 45 hr |
| Apr 1, 2:22 PM MDT | Winter Weather Advisory | BOU | 30 hr |
| Apr 10, 2:51 PM MDT | Winter Weather Advisory | BOU | 63 hr |
| Apr 14, 3:09 PM MDT | Winter Storm Watch | BOU | 19 hr |
| Apr 14, 3:09 PM MDT | Winter Storm Warning | BOU | 51 hr |
| Apr 15, 10:32 AM MDT | Winter Weather Advisory | BOU | 34 hr |
| May 1, 12:47 PM MDT | Mesoscale Discussion | SPC | 88 min |
| May 30, 5:21 PM MDT | Special Weather Statement | BOU | 24 min |
| Jun 6, 12:21 PM MDT | Severe Thunderstorm Watch | SPC | 8 hr |
| Jun 6, 1:51 PM MDT | Severe Thunderstorm Warning | BOU | 39 min |
| Jun 6, 2:33 PM MDT | Severe Thunderstorm Warning | BOU | 42 min |
| Jun 6, 3:03 PM MDT | Severe Thunderstorm Warning | BOU | 57 min |
| Jun 8, 3:42 PM MDT | Winter Weather Advisory | BOU | 19 hr |
| Jun 8, 6:48 PM MDT | Severe Thunderstorm Warning | BOU | 20 min |
| Jun 13, 12:54 PM MDT | Mesoscale Discussion | SPC | 2 hr |
| Jul 6, 3:54 AM MDT | Fire Weather Watch | BOU | 11 hr |
| Jul 6, 3:05 PM MDT | Fire Weather Watch | BOU | 12 hr |
| Jul 6, 3:05 PM MDT | Red Flag Warning | BOU | 29 hr |
| Jul 7, 3:08 AM MDT | Red Flag Warning | BOU | 41 hr |
| Jul 9, 2:35 PM MDT | Red Flag Warning | BOU | 29 hr |
| Jul 13, 2:48 PM MDT | Special Weather Statement | BOU | 42 min |
| Jul 13, 3:00 PM MDT | Severe Thunderstorm Warning | BOU | 45 min |
| Aug 3, 2:12 PM MDT | Mesoscale Discussion | SPC | 93 min |
| Aug 5, 12:27 PM MDT | Mesoscale Discussion | SPC | 2 hr |
| Aug 6, 12:45 PM MDT | Mesoscale Discussion | SPC | 2 hr |
| Aug 13, 3:27 AM MDT | Red Flag Warning | BOU | 17 hr |
| Aug 18, 3:28 AM MDT | Fire Weather Watch | BOU | 12 hr |
| Aug 18, 3:27 PM MDT | Red Flag Warning | BOU | 29 hr |
| Aug 19, 12:41 PM MDT | Fire Weather Watch | BOU | 15 hr |
| Aug 20, 3:43 AM MDT | Red Flag Warning | BOU | 17 hr |
| Sep 4, 2:40 PM MDT | Red Flag Warning | BOU | 3 days |
| Sep 6, 3:12 AM MDT | Winter Storm Watch | BOU | 24 hr |
| Sep 7, 3:39 AM MDT | Winter Storm Warning | BOU | 55 hr |
| Sep 7, 3:39 AM MDT | Winter Weather Advisory | BOU | 55 hr |
| Sep 8, 8:21 AM MDT | Mesoscale Discussion | SPC | 4 hr |
| Sep 23, 2:34 PM MDT | Fire Weather Watch | BOU | 14 hr |
| Sep 24, 4:06 AM MDT | Red Flag Warning | BOU | 40 hr |
| Oct 2, 4:02 AM MDT | Red Flag Warning | BOU | 16 hr |
| Oct 3, 2:23 PM MDT | Fire Weather Watch | BOU | 14 hr |
| Oct 4, 4:01 AM MDT | Red Flag Warning | BOU | 38 hr |
| Oct 12, 3:02 PM MDT | Red Flag Warning | BOU | 27 hr |
| Oct 13, 4:06 AM MDT | High Wind Watch | BOU | 10 hr |
| Oct 13, 1:55 PM MDT | High Wind Warning | BOU | 22 hr |
| Oct 15, 3:24 PM MDT | Red Flag Warning | BOU | 51 hr |
| Oct 16, 1:37 PM MDT | High Wind Warning | BOU | 19 hr |
| Oct 20, 3:35 PM MDT | Red Flag Warning | BOU | 36 hr |
| Oct 21, 3:32 PM MDT | Red Flag Warning | BOU | 27 hr |
| Oct 22, 3:32 PM MDT | Fire Weather Watch | BOU | 12 hr |
| Oct 23, 3:37 AM MDT | Red Flag Warning | BOU | 39 hr |
| Oct 23, 2:46 PM MDT | Winter Storm Watch | BOU | 24 hr |
| Oct 24, 2:41 PM MDT | Winter Storm Warning | BOU | 39 hr |
| Nov 7, 5:12 AM MST | High Wind Warning | BOU | 30 hr |
| Nov 7, 1:21 PM MST | Winter Weather Advisory | BOU | 19 hr |
| Nov 13, 3:22 AM MST | Winter Weather Advisory | BOU | 41 hr |
| Nov 13, 1:45 PM MST | High Wind Warning | BOU | 51 hr |
| Nov 23, 3:30 AM MST | Winter Weather Advisory | BOU | 31 hr |
| Dec 12, 4:47 AM MST | Winter Weather Advisory | BOU | 21 hr |
| Dec 18, 3:19 PM MST | High Wind Watch | BOU | 19 hr |
| Dec 19, 10:30 AM MST | High Wind Warning | BOU | 31 hr |
| Dec 22, 3:52 AM MST | Winter Weather Advisory | BOU | 31 hr |
| Dec 22, 5:06 PM MST | Snow Squall Warning | BOU | 39 min |
| Dec 22, 5:40 PM MST | Snow Squall Warning | BOU | 50 min |
| Dec 22, 6:09 PM MST | Snow Squall Warning | BOU | 66 min |
| Dec 27, 2:14 PM MST | Winter Weather Advisory | BOU | 46 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 |
| Severe Thunderstorm Watch | 1 |
| Mesoscale Discussion | 6 |
| Special Weather Statement | 2 |
| Winter | |
| Snow Squall Warning | 4 |
| Winter Storm Warning | 7 |
| Winter Storm Watch | 7 |
| Winter Weather Advisory | 24 |
| Wind and dust | |
| High Wind Warning | 5 |
| High Wind Watch | 2 |
| Fire | |
| Red Flag Warning | 15 |
| Fire Weather Watch | 7 |
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordForecastThe radar archive20192021
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.