Southwest flow brought above normal Pacific moisture impacting mainly higher elevations of the Northern Rockies where snow amounts between 5 to 8 inches fell.
Every event with a place to put it; 3 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.
Southwest flow brought above normal Pacific moisture impacting mainly higher elevations of the Northern Rockies where snow amounts between 5 to 8 inches fell.
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 1, 2:27 PM MST, 4 hours 26 minutes earlier.
Area Forecast Discussion
National Weather Service Missoula MT
227 PM MST Sat Dec 1 2012
.DISCUSSION...A weak disturbance continues to move through
portions of north central Idaho into southwest Montana this
afternoon causing widespread moderate to heavy rainfall in the
valleys with the higher terrain receiving heavy snow. Behind this
disturbance the Northern Rockies should see a slight decrease in
precipitation, before the next main system moves into the region.
Satellite and models are still showing a very moist system moving
into the region late tonight through Sunday. Snow levels will
remain high for most of this event, so mainly the higher terrain
will be impacted by snow. The mountain passes across the region
will see anywhere from 6 to 15 inches of snow by Sunday afternoon.
The valleys should receive a widespread 0.25 inch of rain with
some places getting over an inch on Sunday. A cold front will
swing through the region on Sunday causing the bulk of the
moisture to be pushed off to the east, but behind the front the
atmosphere will remain unstable with snow levels to valley floors. This
instability should allow for widespread showers and possible snow
bands, so valleys locations could see light snow accumulations by
Monday morning.
Another impact from the system will be the increase in winds prior
to and behind the front. The mountains should see fairly strong
winds during this event, so the combination of winds and snow
could cause periods of white out conditions at mountain passes. So
a winter storm warning or advisory has been issued for the higher
terrain starting late tonight and lasting through the evening
hours. The models are still indicating that the Riggins region
onto the Camas prairie of Idaho should see strong southerly winds
early Sunday morning, so a wind advisory has been issued for the
area.
Tuesday through Thursday...A wet pattern will continue. The wettest
period being late Tuesday and Wednesday ahead of a strong cold frontal
passage Wednesday night. Snow levels will around or below pass level.
snow amounts are uncertain at this time however accumulating snows are
likely and will impact travel over mountain passes. The other impact
from this system will be increasing southerly winds in the camas prairie
ahead of the front.
Showery conditions are likely through the end of the week behind the
frontal passage. Models are hinting at arctic air moving into the
region however there is quite a bit of inconsistency between model
solutions regards to location of the coldest air. Some models keep
it well east of the divide while another has it brushing the
continental divide. stay tuned for updates.
&&
.AVIATION...A fairly strong band of showers has pushed through
KMSO and is expected to stay just to the north and west of KBTM.
Gusty south southwest winds will begin to increase for all
aviation sites this afternoon after 01/22Z and persist till just
after dark. Due to the recent rainfall fog and low stratus will be
a threat once more for KMSO, KGPI, and possibly KGPI after 02/06Z.
Low to mid level clouds will continue to obscure mountain tops for
the rest of the evening.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WARNING from 11 PM this evening to 5 PM MST Sunday
ABOVE 4500 FEET FOR THE Bitterroot/Sapphire Mountains...
Lower Clark Fork Region.
WINTER STORM WARNING from 5 AM to 11 PM MST Sunday ABOVE 5000
FEET FOR THE Potomac/Seeley Lake Region...West Glacier
Region.
WINTER WEATHER ADVISORY from 5 AM to 11 PM MST Sunday ABOVE 6000
FEET FOR THE Butte/Blackfoot Region.
ID...WINTER STORM WARNING from 10 PM this evening to 4 PM PST Sunday
ABOVE 4500 FEET FOR THE Northern Clearwater Mountains...
Southern Clearwater Mountains.
WIND ADVISORY from 1 AM to 1 PM PST Sunday Lower Hells
Canyon/Salmon River Region...Orofino/Grangeville Region.
WINTER STORM WARNING from 11 PM this evening to 5 PM MST Sunday
ABOVE 6000 FEET FOR THE Eastern Lemhi County.
&&
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https://www.twitter.com/NWSMissoulaThe national radar mosaic for the moment the first event began.
1 heavy snow, 1 winter weather, 1 winter storm. Local standard time, as filed.
Lookout Pass ski resort reported 8 inches of snow in the 24 hours ending at 1427MST Dec. 2. Montana DOT required chains on towing units at the Lookout Pass at 0430MST. Snow-covered roads were reported from St. Regis to Lookout Pass.
Slick roads were blamed for a fatal car accident that occurred on highway 12 near mile marker 14 approximately 1.5 miles ESE of Avon, MT.
Approximately 6 inches of snow fell at Marias Pass while air temperatures ranged between 31 and 34 degrees F. This created slick conditions along U.S route 2 east of Essex. Towards the end of the event, winds were gusting up to 52 mph which created brief periods of blowing snow.
As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.
| Event | Date | Age | Sex | Where | Kind |
|---|---|---|---|---|---|
| Winter Weather, Butte / Blackfoot Region | 2012-12-02 | 41 | Male | Vehicle/Towed Trailer | Indirect |
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: 422492, 422479, 426459.