A broad and cold upper level trough of low pressure moved over the northern Rockies, providing moisture to most locations across western Montana and north central Idaho. Snow levels lowered enough to impact mountain passes with accumulating snow.
Every event with a place to put it; 1 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS MSO wrote it up.
A broad and cold upper level trough of low pressure moved over the northern Rockies, providing moisture to most locations across western Montana and north central Idaho. Snow levels lowered enough to impact mountain passes with accumulating snow. Total amounts ranged between four to seven inches.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Missoula, MT wrote its last area forecast discussion before the first event at May 22, 1:50 PM MST, 3 hours 10 minutes earlier.
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</html>The national radar mosaic for the moment the first event began.
1 heavy snow. Local standard time, as filed.
A trained spotter in Divide reported seven inches of new snow. A trained spotter five miles southwest of Butte reported nine inches of new snow. Five of those inches fell in about three hours.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2010Every state in 2010This day in weather historyWarnings in Montana, May 2010
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-30. Each event’s entry at NCEI: 230856.