A very strong atmospheric river event brought very heavy snow to the southeast Idaho mountains and the Sun Valley region. Amounts of over 2 feet of snow were very common in the drawn out event.
Every event with a place to put it; 12 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 PIH wrote it up.
A very strong atmospheric river event brought very heavy snow to the southeast Idaho mountains and the Sun Valley region. Amounts of over 2 feet of snow were very common in the drawn out event. 51 inches of snow fell at Bald Mountain at the Sun Valley ski resort and the resort shut down January 29th after several avalanches and the death of a skier.
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 Pocatello, ID wrote its last area forecast discussion before the first event at Jan 27, 2:43 AM MST, 1 hour 17 minutes earlier.
Area Forecast Discussion National Weather Service Pocatello ID 243 AM MST Wed Jan 27 2021 .SHORT TERM...Today through Friday night. Our multiple day storm event is starting to unfold across central and eastern Idaho. As expected, we are seeing some lighter snow and slick spots across highlands along and east of I-15, as well as across portions of the Arco Desert and central mountains. What we are seeing is a bit more than forecast, but impacts are still on the lower end. Snow will increase during the day, with the biggest impact areas lying across portions of the central mountains, Island Park/Big Holes, the Magic Valley/Snake Plain from the Lava Beds north of Shoshone to north and east Idaho Falls/Rexburg. Those areas remain under Winter Storm Watches or Winter Weather Advisories through the duration of the storm. We also have a Winter Weather Advisory for the Caribou and Bear River Ranges, but impacts may end up being a little less than previously expected as snowfall farther south seems to be decreasing a bit overall. Stronger southerly winds will create some pockets of blowing and drifting. The south to southwest flow will still produce some downslope conditions and shadowing. We are still looking at much lower snow amounts once you get to the Stanley Basin and Challis area. Downslope is still a big concern along the 84/86 corridor, as well as along I-15 up through Idaho Falls. The models are still trying to paint some light snowfall in those areas, especially once you get around Pocatello northeast toward Idaho Falls and Rexburg. The biggest potential of that happening would be through tonight/Thursday morning, BUT the downslope will likely greatly limit snowfall once you get around Blackfoot and points south and west. The most likely scenario is that we MAY see snow falling, but melting or lightly accumulating on grassy areas. We would not be surprised if the downslope along the 84/86 corridor is strong enough to produce nothing more than sprinkles/flurries until the front arrives Friday. The Teton Valley north of Victor toward Driggs and Tetonia is another likely spot to see much lower snowfall due to south winds. The trend for Thursday is heavier snow continuing in our Warning/Advisory locations favored in south/southwest flow, with a secondary push across the southeast highlands. Elsewhere, precipitation decreases and temperatures warm up enough where it may actually be a mix or light rain across lower elevations. Confidence drops quite a bit Thursday night and Friday, as snow should continue in upslope areas farther north...but decrease for a short period until the front arrives later Friday. Some of the models and ensembles are significantly drier overall Friday while others remain on the wet side of the spectrum. The forecast is a blend of the two with an increasing chance of light precipitation Friday. Keyes .LONG TERM...Saturday through Wednesday. The weekend will represent the best chance at a break in slowly progressive deep pattern. There could be some light lingering precipitation both days over higher elevations in Central ID and the eastern highlands along the WY border, in areas where westerly orographics can help induce precipitation. Otherwise expect most areas to remain dry under influence of weak transitory ridge. Pattern shifts to deep and moist south flow again early in the week, with next Pacific low beginning to shift precipitation into East Idaho Monday night into Tuesday. Ensembles favor Tuesday and Tuesday night as the best chance for precipitation, but there is some wiggle room into Monday night and Wednesday for start and end. This pattern would again favor the same areas targeted with the current system, mainly the southern upslope regions of the central mountains, and the far northeast corner. Potential exists for another respectable snow-maker for these areas, though the system does not look to be a multi-day event as it is already exiting the region by late Wednesday in most ensemble members. Colder temperatures at onset may be more favorable for accumulations in lower elevations as well, but of course devil will be in the details as orographics are expected to once again play a significant role for some locations in either promoting or inhibiting precipitation potential. DMH && .AVIATION...Mix of conditions is now occurring across East Idaho as deep Pacific low is starting to shift into the region. To the south, pockets of light snow have developed across the southern highlands. The gusty south winds are contributing to low level wind shear concerns along the I-86/I-84 corridor, mainly KPIH and KBYI terminals. Further north, broad area of light snow from KSUN east to KIDA and KDIJ is producing MVFR ceilings and visibility. Expectations are for the MVFR conditions to continue through the day with periods of light to moderate snowfall, and each of those terminals may see occasional IFR conditions this afternoon and overnight. KBYI and KPIH may also see a brief period of snowfall this afternoon, but the strong southerly flow just off the surface will be a big inhibitor and is contributing to a lot of uncertainty at this time. Expectations are that conditions would remain MVFR or better, even if some snow can be realized today and tonight. DMH && .PIH WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 5 AM MST Friday for IDZ051>053-067- 068. Winter Storm Warning until 5 AM MST Friday for IDZ069-072>075. Winter Storm Warning until 11 PM MST Friday for IDZ064-066. Winter Weather Advisory until 11 PM MST Friday for IDZ060-063. &&
The national radar mosaic for the moment the first event began.
10 heavy snow, 1 avalanche, 1 winter weather. Local standard time, as filed.
Eleven inches of snow fell at the onset of the storm from the 27th into the 28th at Darlington as measured by a spotter. Butte County School District 111 was closed due to the heavy snow and hazardous travel conditions on the 28th.
Extremely heavy snow fell in the Wood River Foothills. The COOP observer in Bellevue measured 12 inches of snow the first two days of the event through the 28th. The Hailey region had several reports of between 25 and 40 inches of snow for the event.
Heavy snow fell in the Beaverhead and Lemhi Highlands region. The COOP observer at Dubois measured 12 inches and the COOP observer at Small measured 11 inches.
Estimated SNOTEL amounts were 42 inches at Hilt's Creek and 15 inches at Meadow Lake.
SNOTEL estimated snow totals were 35 inches at Bear Canyon, 24 inches at Garfield Ranger Station, 31 inches at Smiley Mountain, 18 inches at Stickney Mill, and 45 inches at Swede Peak.
During first day and a half of storm Craters of the Moon measured 15 inches of snow. Butte County School District 111 closed on the 28th due to the very heavy snow and hazardous travel conditions.
An estimated 40 inches of snow fell at the Vienna Mine SNOTEL site.
An atmospheric river event brought extreme snowfall amounts to the Sun Valley region over several days. 33.5 inches was measured by the COOP in Ketchum. Other amounts estimated at SNOTEL sites were: Chocolate Gulch 31 inches, Dollarhide Summit 42 inches, Galena 17 inches, Galena Summit 43 inches, Hyndman 21 inches, and Lost Wood Divide 29 inches. Bald Mountain at summit of Sun Valley ski resort measured 51 inches of snow. A 67 year old male died while skiing on January 29th in the extremely deep snow from asyphixiation after suffering an accident.
Estimated SNOTEL snow amounts were 25 inches at Crab Creek, 14 inches at Island Park, and 28 inches at White Elephant.
Estimated SNOTEL snowfall were 15 inches at Emigrant Summit and 13 inches at Franklin Basin.
Back country skiers triggered avalanches on the Warm Springs side of Bald Mountain. Skiing operations were shut down on the afternoon of the 29th due to avalanche mitigation at Sun Valley ski resort. Substantial debris from one of the avalanches caused debris on Warm Springs Road near Ketchum on the 29th. The debris buried two vehicles. Warm Springs Road was only open to residents.
Very strong winds caused extensive blowing and drifting of snow and whiteouts on Idaho route 32. It was closed around noon on the 30th from Ashton to Tetonia between Idaho 47 and Idaho 33.
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 |
|---|---|---|---|---|---|
| Heavy Snow, Sun Valley Region | 2021-01-29 | 67 | Male | Outside/Open Areas | Indirect |
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2021Every state in 2021This day in weather historyWarnings in Idaho, January 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: 937236, 937240, 937280, 937284, 937285, 937235, 937294, 937230, 937291, 937283, 937231, 937314.