Enough moisture from the Pacific Ocean and enough of a disturbance riding up and over the Rocky Mountains combined to spread accumulating snow across portions of northeast Montana. While most locations only received up to four inches of snow, western Valley County accumulated more.
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 GGW wrote it up.
Enough moisture from the Pacific Ocean and enough of a disturbance riding up and over the Rocky Mountains combined to spread accumulating snow across portions of northeast Montana. While most locations only received up to four inches of snow, western Valley County accumulated more.
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 Glasgow, MT wrote its last area forecast discussion before the first event at Dec 4, 3:35 AM MST, 1 hour 25 minutes earlier.
Area Forecast Discussion National Weather Service Glasgow MT 335 AM MST Sat Dec 4 2021 .DISCUSSION... ...Winter Storm to bring accumulating snow to NE Montana today... A band of precipitation appears to be setting up over the southwest zones looking at the radar presentation, though nearby observations suggest this is taking some time to reach the ground. Do expect snowfall to initiate this morning and become heavier as this band lifts northeast during the day. The steadiest snowfall rates will shift to the northern zones by this afternoon and evening, with lingering snow showers a possibility tonight and Sunday as the system departs. It should be pointed out that before the colder temperatures wrap around the backside of this system, a transition to wintry mix is possible across southern areas this afternoon as soundings show a nice warm nose. Otherwise, do expect a trend toward colder temperatures behind this system, which will continue into early next week. Fresh snow cover may allow for increased radiational cooling should any clearing occur during the nighttime, and that is where uncertainty lies with an active weather pattern in hand. Another shortwave may drop across the region with light snow on Monday into Tuesday. A shallow ridge behind that system will likely lead to modifying temperatures for the middle of the week as daytime highs approach or exceed the freezing mark. Considerable uncertainty in the forecast develops beyond that point at later time scales with the usual spread in long term ensemble spread. && .AVIATION... Expect a range of VFR to IFR conditions today. Flight conditions will deteriorate as a band of snow lifts northeast today. This will lead to associated drops in ceilings and visibility. Low stratus as well as snow showers may linger into tonight and Sunday. Winds will increase today, southeast at 10 to 20 kts with gusts to 30 kts from late morning into the afternoon. Winds will switch northwest between 04-07Z tonight. && .GLASGOW WATCHES/WARNINGS/ADVISORIES... Winter Storm Warning until 5 AM MST Sunday for Daniels...Eastern Roosevelt...Northern Phillips...Northern Valley...Sheridan... Western Roosevelt. Winter Weather Advisory until 11 AM MST this morning for Petroleum...Southwest Phillips. Winter Weather Advisory until 5 AM MST Sunday for Central and Southeast Phillips...Central and Southern Valley...Dawson... Garfield...McCone...Richland. && weather.gov/glasgow
The national radar mosaic for the moment the first event began.
1 heavy snow. Local standard time, as filed.
Trained spotter at Hinsdale 4 SW measured 7 inches of snow. Times are estimated.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2021Every state in 2021This day in weather historyWarnings in Montana, December 2021
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 2026-09-24. Each event’s entry at NCEI: 995960.