Severe Thunderstorm Warnings in Montana, 2011

By month

190 of 413 severe thunderstorm warnings covering Montana in 2011 had a qualifying storm report inside them; 318 of 441 hail, wind and damage reports fell inside a warning, on average 23 minutes after it went out.

Montana, 2011

Each office's whole area, 2011

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.

• Valley County62
• Phillips County52
• Rosebud County36
• Garfield County36
• Carter County35
• Yellowstone County34
• McCone County33
• Roosevelt County33
• Big Horn County33
• Custer County30
• Powder River County25
• Daniels County25
• Dawson County23
• Musselshell County23
• Stillwater County22
• Sheridan County21
• Richland County21
• Cascade County20
• Fallon County19
• Chouteau County18
• Prairie County16
• Golden Valley County15
• Treasure County15
• Wibaux County15
• Blaine County13
• Petroleum County12
• Lewis and Clark County12
• Fergus County11
• Sweet Grass County11
• Carbon County9
• Hill County8
• Flathead County7
• Judith Basin County6
• Broadwater County6
• Meagher County6
• Teton County6
• Wheatland County6
• Missoula County5
• Gallatin County3
• Powell County3

1. July 15, 201125severe thunderstorm warnings
2. June 7, 201120severe thunderstorm warnings
3. July 22, 201120severe thunderstorm warnings
4. July 26, 201119severe thunderstorm warnings
5. August 11, 201119severe thunderstorm warnings
6. June 2, 201118severe thunderstorm warnings
7. July 13, 201118severe thunderstorm warnings
8. July 17, 201117severe thunderstorm warnings
9. July 14, 201115severe thunderstorm warnings
10. July 16, 201115severe thunderstorm warnings
11. June 30, 201113severe thunderstorm warnings
12. July 4, 201113severe thunderstorm warnings

Alerts in force nowTornadoes on recordThe radar archive20102012

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.