A second push of Arctic air came over the Continental Divide bringing windy conditions and low wind chill values.
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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 second push of Arctic air came over the Continental Divide bringing windy conditions and low wind chill values.
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 Feb 10, 2:46 AM MST, 5 hours 6 minutes earlier.
Area Forecast Discussion National Weather Service Missoula MT 246 AM MST Wed Feb 10 2021 .DISCUSSION...Light snow will continue again today over west central Montana and central Idaho where another inch is possible. The best time period for light accumulations in west central Montana will be late day into the early evening as a short wave drops through the area, reinvigorating showers and possibly initiating bands. Areas north and east of Missoula Valley that are already cold, will get a couple more degrees colder today and tonight. Thursday, you guessed it light snow for west central Montana and central Idaho. In the Clearwater Mountains snow intensities will begin to ramp up late in the day as moisture from the southwest overruns the area. The difference in temperatures is that the Arctic air is expected to push into the Bitterroot Valley reducing temperatures in Missoula and south by 10 - 20 degrees. Overnight Thursday into Friday, there is uncertainty in how far north the moisture will go. To give you an example, the ensembles have available moisture for west central Montana increase slightly from the past several days. So a good bet would be 2 to 3 inches for the Missoula Valley and I-90 corridor. The Bitterroot Valley should have better moisture and our forecast there calls for 3 to 6 inches. The big winner at this time will be the Clearwater Mountains as there is no dry Arctic air to overcome and up to a foot of snow for the mountains is expected. Even the Camas Prairie in Idaho will see light to moderate snow and by Friday afternoon expect 4 to 8 inches. This will also be the time period that the Arctic air mass moves south over Missoula and the Bitterroot Valleys bringing strong winds, therefore blowing and drifting of snow on roads is expected, which will cause reduced visibilities. Thursday and Friday, temperatures will remain extremely cold over Western Montana. Add in wind, and wind chills will become extreme in northwest Montana and along the Continental Divide, where the coldest valleys could see wind chill values as low as -50F. Even the Missoula and Bitterroot Valleys will join the in the dangerous wind chills as values will range at times from -20 to -30. Finally, this weekend the models diverge somewhat in placement of precipitation. There will be another trough pushing south and west of our area and we have light snow for the Clearwater Mountains. That said, some model solutions have moisture as far north as I-90 once again, please check back to see how future runs of the models resolve this difference. On temperatures, the models do agree that finally this cold air mass will begin to move east out of the Northern Rockies and we will moderate back towards seasonably cold temperatures as opposed to dangerously cold. && .AVIATION...Light snow will continue throughout the day at KMSO, with the best chance for lower visibilities and ceilings between 10/2200z and 11/0600z. KBTM is currently IFR due to low stratus, this is due to very cold air settling in the valley. As the morning progresses and the surface dries out, the stratus will slowly lift. Both KGPI and KSMN are expected to continue with VFR conditions through noon, when northeast winds will develop at KGPI and blowing snow may develop reduced visibilities at times. Thursday evening the next weather system will begin to affect central Idaho, causing terrain obscurations. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. &&
The national radar mosaic for the moment the first event began.
5 extreme cold/wind chill. Local standard time, as filed.
Wind gusts of 20-30 miles per hour and well below zero air temperatures resulted in extended periods of wind chills of -30F to -50F. The coldest observed wind chill was -70F at the Snowslip sensor above US Highway 2.
An extended period of wind chills ranging from -35F to -55F was observed.
Wind chill values of -30F to -40F were common through the period.
Wind chills bottomed out at -30F during the early morning hours in the Missoula Valley.
Wind chill values of -25F to -35F were observed as winds gusted to 40 mph with air temperatures near zero.
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, February 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: 937885, 937888, 937890, 937889, 937886.