An atmospheric river brought very heavy snow to north-central Idaho that triggered multiple impacts including treefall, avalanche, road closures, and hazardous travel.
Every event with a place to put it; 7 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.
An atmospheric river brought very heavy snow to north-central Idaho that triggered multiple impacts including treefall, avalanche, road closures, and hazardous travel.
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 Jan 4, 1:52 PM MST, 7 hours 8 minutes earlier.
Area Forecast Discussion
National Weather Service Missoula MT
152 PM MST Tue Jan 4 2022
...HEAVY SNOW THURSDAY AND FRIDAY ACROSS THE REGION...
.DISCUSSION...Tonight and tomorrow the light to moderate snow
continues, which will be a nuisance for travel conditions. Also,
an arctic air mass east of the Continental Divide is seeping
through the passes today. Tonight a shortwave will drop out of
Canada and cause some of the those snow showers as well as helping
to push more of that cold air across the Continental Divide and
into the valleys of western Montana.
Once that cold air is in place, an atmospheric river will set up
Wednesday night and Thursday. As the moist air from the southwest
streams into the area over the recently deposited cold air, heavy
snow will ensue. Many mountain locations will receive over 2 feet
of snow in 2 days ending Friday.
The valley locations south of Interstate 90 are more
complicated. Once the atmospheric river gets started, south winds
will set up and start to erode the cold pools out of the valleys.
So snow levels will start to rise on Thursday, but they've got a
long way to go. The Camas Prairie in Idaho is the focus of
uncertainty in this forecast. The strength of the cold air at the
surface in that area will battle against the warm air coming in.
Freezing rain is possible, but many lower elevation areas will
probably turn to rain on Thursday. The forecast is messy there,
and we have a winter weather advisory out for that region. There
is a possibility that the cold air in that region remains in place
long enough that more snow than rain falls. If that is the case,
we may need to upgrade the advisory in that area to a warning.
We'll be watching it closely.
In western Montana, freezing rain is a possibility also, but much
less likely at this time. Model soundings show the atmospheric
river to be cold enough that combined with the cold pools it will
most likely remain snow or a snow rain mix. Two areas we are
watching closely though are the southern Bitterroot Valley and the
area around Hot Springs. These areas are on the southern end of
their respective valleys and will be the first to break out of the
cold air if they do.
Thursday morning during the morning commute Missoula will see it's
heaviest snow, making for a difficult commute. Not only will this
be the period of heaviest snow in Missoula, but it will also have
been snowing for several hours already.
By Friday, the models are really struggling with how to handle the
cold pools. By that time the southerly flow will have had much
more time to erode the cold pools. The forecast uncertainty and
the potential for some freezing rain increases in the southern
Bitterroot. The weather pattern fits with a potential freezing
rain scenario, so it's hard to not worry about it. However, models
are currently keeping the warm layer aloft shallow and near the
ground, so when you take that into account it's difficult to get
the set up for freezing rain we need, and the forecast isn't
mentioning freezing rain as the most likely event as a result.
It's another thing we'll be watching closely though.
Saturday some mountain snow will continue, but things will be on a
sharp downward trend. Then a ridge builds Saturday night and
Sunday, so next week will see much less active weather.
&&
.AVIATION...Scattered snow showers will continue to move over the
Northern Rockies this afternoon and early evening. Overnight a
shortwave will move through the region, and will bring widespread
light to moderate snow to the area. At the same time, the
shortwave will aide in an arctic airmass in moving further west
and south through western Montana. KPGI can expect snow from
05/0100-05/0600 this evening, before the northeast winds arrive
cutting off the snow accumulations. The best time for the gusty
winds will be from 05/0600-05/1400Z with gusts up to around 25kts.
KMSO can expect continuous snow starting around 05/0800Z tonight,
and picking up in intensity between 05/1200-05/1800Z. Lighter
intensities are expected throughout the day. Late Wednesday night
through the day on Thursday an Atmospheric River will bring
copious amounts of moisture and overrunning the arctic airmass
already in place, producing moderate to heavy snow for most of
the Northern Rockies.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory from midnight tonight to 3 PM MST
Wednesday Butte/Blackfoot Region.
Winter Storm Watch from Wednesday afternoon through Saturday
morning Bitterroot/Sapphire Mountains.
Winter Weather Advisory from 9 PM this evening to 5 PM MST
Wednesday Bitterroot/Sapphire Mountains.
Winter Weather Advisory from midnight tonight to 5 PM MST
Wednesday Missoula/Bitterroot Valleys.
Winter Storm Watch from Wednesday afternoon through Friday
evening Missoula/Bitterroot Valleys.
Winter Storm Watch from Wednesday evening through Saturday
morning Kootenai/Cabinet Region...Lower Clark Fork Region.
Winter Weather Advisory from midnight Wednesday night to
midnight MST Friday night Flathead/Mission Valleys.
Winter Storm Watch from late Wednesday night through Saturday
afternoon West Glacier Region.
Winter Storm Watch from Wednesday afternoon through late
Thursday night Potomac/Seeley Lake Region.
ID...Winter Weather Advisory from midnight tonight to 8 PM MST
Thursday Eastern Lemhi County...Western Lemhi County.
Winter Storm Watch from Wednesday afternoon through Saturday
morning Northern Clearwater Mountains...Southern Clearwater
Mountains.
Winter Weather Advisory from 8 PM this evening to 4 PM PST
Wednesday Northern Clearwater Mountains...Southern
Clearwater Mountains.
Winter Weather Advisory from 4 PM this afternoon to 4 PM PST
Thursday Lower Hells Canyon/Salmon River Region...
Orofino/Grangeville Region.
&&The national radar mosaic for the moment the first event began.
6 heavy snow, 1 avalanche. Local standard time, as filed.
Heavy snow fell, ranging from 16 inches in Salmon to 22 inches in Gibbonsville over a 3 day period, and caused difficult travel in Lemhi County.
Williams Creek Summit received between 18 and 24 inches of snowfall.
A CoCoRaHS spotter located 3 miles southwest of Riggins reported 10.4 inches of snow in 3 days ending on the 7th. When compared to the longer Riggins climate record, this is within the top 10 highest snowfall for that area. The Riggins school closed due to heavy snow.
More than 2 feet of heavy snow fell across the region with the Idaho Department of Transportation stating that the snow rates were up to 3 inches per hour at times. US-12 between Kooskia and Powell was closed from 2 pm PST Jan. 6 through 4 pm Jan. 9 due to avalanche and treefall danger. It was estimated that 150 trees fell due to the weight of the snow along the highway. Also a large avalanche occurred at milepost 136. Power outages were reported east of Kooskia and also in the Elk City area.
Heavy snowfall totals amounted to around 2 feet in the area which resulted in poor driving conditions and a few power outages. Pierce received a 3 day snowfall total of 20.6 inches through the 7th, which was the 7th highest snowfall during any time of the year since 1963.
Heavy snow amounts during this event included 10 inches on the Camas Prairie, 12.5 inches in Orofino, 14.8 inches located west-northwest of Orofino, and 18.5 inches in Woodland. Multiple trees fell onto US-12 between Orofino and Kamiah which halted plowing operations and damaged power lines. Besides a plethora of power outages, there were area-wide school closures and delays.
A large avalanche, more than 10 feet deep and up to 40 feet wide was triggered by heavy snow near milepost 136 on US-12. This along with treefall caused the highway to be closed for 3 days. The last time an avalanche crossed US-12 was in 2008. The date and time of the avalanche is a coarse estimate.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2022Every state in 2022This day in weather historyWarnings in Idaho, January 2022
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: 1004381, 1005436, 1004380, 1004361, 1004347, 1004377, 1004370.