Several organized and unusually long west-to-east oriented bands of heavy snow developed across north-central Idaho by late afternoon and moved into western Montana by the evening hours on December 7. Snowfall rates of up to 3 inch per hour were reported underneath the bands.
Every event with a place to put it; 9 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.
Several organized and unusually long west-to-east oriented bands of heavy snow developed across north-central Idaho by late afternoon and moved into western Montana by the evening hours on December 7. Snowfall rates of up to 3 inch per hour were reported underneath the bands. Multiple car accidents and slide-offs were also reported during this event.
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 Dec 6, 2:17 PM MST, 2 hours 43 minutes earlier.
Area Forecast Discussion
National Weather Service Missoula MT
217 PM MST Thu Dec 6 2012
...Travel impacted by accumulating snow tonight through the weekend...
.DISCUSSION...Snow showers have begun to fall across much of
western Montana, and will continue to further develop as the
evening continues. A cold front expected to cross the region
late tonight will cause an intensification of snowfall, beginning
first across northwest Montana in the early morning hours. Snow will
then spread across the rest of western Montana and central Idaho
through the day Friday. Mountain passes will see the heaviest
snowfall, with up to one foot of accumulation possible by Friday
night. Impacts to travel over Marias, Lookout, and Lolo passes
will be high due to slippery roadways and lowered visibilities.
Down in the valleys, snow is also expected, and will have a very
high chance of sticking to roadways as well. The Flathead/Mission
valleys could see anywhere between 3 to 5 inches, with valleys to
the south, including Missoula valley, could see 1 to 3 inches.
Road surfaces should remain cold enough to support snow coverage,
but by Friday afternoon, some roads may warm enough to convert
snow to wet slush. In any case, several Winter Weather Advisories
have been issued across western Montana to address travel impacts
from snow.
A surface cold front will continue moving south across the
Northern Rockies during Friday evening, resulting in accumulating
snow/ice and impacting travel throughout the region. Snow will
likely taper off during overnight Friday, as the system moves
south and east of the area. Meanwhile, relatively cold Canadian
air will move west of the Continental Divide and into the western
Montana valleys. Temperatures are likely to be the coldest thus
far this winter during the weekend, increasingly the likelihood
for ice accumulations to remain on roadways and sidewalks through
early next week. Snow will not leave the weather picture either
during the remainder of the weekend, with periods of light snow
possible. Confidence has decreased over the threat of freezing
rain for northwest Montana overnight Sunday through Monday
morning, however a slight chance remains in the forecast as the
pattern is still shows favor of such an occurrence.
Otherwise, temperatures will very slowly moderate across the
region on Monday.
The models are showing another disturbance over the Northern Rockies
by the middle of next week. The models diverge greatly on how this
system will move through the region, but at this time the chance
for precipitation will be above normal. Meanwhile, temperatures appear
to be near normal readings during the extended forecast periods.
&&
.AVIATION...Snow showers will impact KGPI and KMSO terminals through
the night tonight, intensifying further during the day Friday. Lowered
visibilities will be common, with lowered ceilings also likely.
Northwest Montana and west central Montana will see the brunt of
the snowfall, with the expectation of easing up by late Friday
night. KBTM and KSMN will also see a chance for snow showers, but
heavy snow is not expected for these locations.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY until 11 PM MST Friday
Bitterroot/Sapphire Mountains...Flathead/Mission Valleys...
Kootenai/Cabinet Region...Lower Clark Fork Region...West
Glacier Region.
WINTER WEATHER ADVISORY until 11 PM MST Friday
Missoula/Bitterroot Valleys.
WINTER WEATHER ADVISORY until 11 PM MST Friday Potomac/Seeley
Lake Region.
ID...None.
&&
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https://www.twitter.com/NWSMissoulaThe national radar mosaic for the moment the first event began.
9 heavy snow. Local standard time, as filed.
Law enforcement reported heavy snow at MT-2 near Happy's Inn with 4 to 6 inches on the road surface. They estimated 10 to 12 inches fell there in the last 24 hours.
A member from the public reported an estimated 24 inches of snow that fell one mile north of Essex. They reported that highway 2 north of Essex was down to one lane on the morning of December 8.
A COOP observer 2 miles NNE of Missoula reported 8.8 inches of snow.
The Missoula International airport received 8.1 of snow from the heavy snow showers. In a 35 minute period from 1935 to 2000MST on December 7th, 1.7 inches of snow fell at the Missoula NWS office.
At 2100MST, the Montana Highway Patrol reported multiple car accidents during the evening across west-central Montana due to heavy snow causing slick roads and reduced visibilities. At one point, an eastbound section of Interstate 90 shut down west of Missoula.
At2100 MST, the Montana Highway Patrol reported multiple car accidents during the evening along Interstate 90 west of Missoula due to heavy snow causing slick roads and reduced visibilities. At one point, an eastbound section of Interstate 90 was temporarily closed.
A trained spotter 5 miles southeast of Creston called to report 8 inches of snow that fell mainly between 1800 and 2230MST. They also reported that the heaviest snow amounts fell east of Highway 35 from the Many Lakes Rd. south to just north of Bigfork. The roads were snow-covered and very slick.
A trained spotter from Huson reported heavy snow with visibilities less than one quarter mile while roads were snow-covered. The two hour snowfall total was 3.5 inches.
Montana DOT listed severe driving conditions from Interstate 90 from Tarkio to Frenchtown due to the heavy snow.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2012Every state in 2012This day in weather historyWarnings in Montana, December 2012
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: 426715, 424629, 422495, 422494, 423845, 424621, 424628, 424624, 424637.