Weather alerts in Montana, 2010
2,193 weather alerts in 2010, from the National Weather Service and the Storm Prediction Center. An alert counts here when it covered any part of the state, so the counties below add up to more than the state.
Weather alerts by county
Each county as a circle sized by its count in 2010. Tap one for its archive.
- Alerts
- 2,193
- Warnings
- 693
- Watches
- 142
- Advisories
- 456
- Busiest month
- July479 alerts
- Busiest day
- August 1, 201066 alerts
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
13 of 56 tornado warnings covering Montana in 2010 had a tornado report inside them; 17 of 39 tornado reports fell inside a warning, on average 15 minutes after it went out.
Montana, 2010
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 56 | 13 | 77% | 39 | 44% | 15 min |
| Severe thunderstorm warnings | 446 | 225 | 50% | 539 | 68% | 23 min |
| Flash flood warnings | 24 | 3 | 88% | 14 | 21% | 122 min |
Each office's whole area, 2010
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Missoula, MT: tornado warnings | 0 | 1 | 0% | |||
| NWS Missoula, MT: severe thunderstorm warnings | 53 | 23 | 57% | 67 | 55% | 19 min |
| NWS Missoula, MT: flash flood warnings | 7 | 0 | 100% | 2 | 0% | |
| NWS Great Falls, MT: severe thunderstorm warnings | 68 | 40 | 41% | 96 | 67% | 21 min |
| NWS Great Falls, MT: flash flood warnings | 2 | 1 | 50% | 1 | 100% | 106 min |
| NWS Glasgow, MT: tornado warnings | 25 | 5 | 80% | 23 | 43% | 14 min |
| NWS Glasgow, MT: severe thunderstorm warnings | 181 | 104 | 43% | 216 | 74% | 26 min |
| NWS Glasgow, MT: flash flood warnings | 2 | 0 | 100% | 5 | 0% | |
| NWS Billings, MT: tornado warnings | 31 | 8 | 74% | 16 | 44% | 16 min |
| NWS Billings, MT: severe thunderstorm warnings | 168 | 68 | 60% | 200 | 67% | 22 min |
| NWS Billings, MT: flash flood warnings | 17 | 3 | 82% | 8 | 50% | 73 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
2,193 alerts are too many to list on one page. Narrow it to a product above, to a month in the chart, or to a county.
By product
Every kind of product issued here, grouped by hazard. Each opens the same place narrowed to that product.
By county
Every county with at least one alert. A county page lists each alert that covered it.
- McCone County262
- Valley County259
- Roosevelt County215
- Richland County201
- Garfield County199
- Phillips County193
- Dawson County186
- Carter County171
- Sheridan County169
- Rosebud County167
- Big Horn County162
- Daniels County160
- Missoula County158
- Wibaux County158
- Prairie County153
- Powder River County153
- Custer County146
- Granite County142
- Petroleum County139
- Ravalli County138
- Stillwater County132
- Fallon County129
- Powell County127
- Lake County125
- Flathead County117
- Yellowstone County114
- Park County110
- Sweet Grass County110
- Treasure County109
- Silver Bow County107
- Carbon County101
- Deer Lodge County100
- Sanders County97
- Musselshell County96
- Golden Valley County91
- Wheatland County83
- Mineral County69
- Fergus County69
- Judith Basin County69
- Chouteau County59
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordThe radar archive20092011
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.