One of the most significant winter storms of the season will slam into East Idaho late Monday night, bringing heavy mountain snow, dangerous winds and treacherous travel conditions through Thursday morning after months of unusually mild winter conditions.
The National Weather Service has issued a winter storm warning for the Emigration Summit area and Bear River mountain range — which spans parts of Bear Lake, Franklin and Caribou counties — one of the few such warnings issued in East Idaho this winter. Forecasters expect a staggering 20 to 30 inches of snow above 7,000 feet and 12 to 18 inches below that elevation from Monday night through early Thursday in those areas.
"Travel could be very difficult to impossible," the weather service warned about areas under the winter storm warning.
The storm's reach extends far beyond Idaho's borders. Winter weather warnings are in effect across all states surrounding Idaho, and winter weather advisories blanket most of the Gem State, including much of East Idaho.
While mountain areas will bear the brunt of the storm, population centers in the Snake River Plain — including Pocatello, Chubbuck, Blackfoot, Idaho Falls, Ammon and Rexburg — will see less snow but still face hazardous conditions from powerful winds and icy roads.
The winds will compound the danger across the region. A wind advisory covers much of East Idaho from 11 p.m. Monday to 9 a.m. Tuesday, with southwest winds of 20 to 30 mph and gusts up to 50 mph bearing down on Idaho Falls, Ammon, Pocatello, Chubbuck, Blackfoot, Rigby, Shelley, Firth, Rexburg, St. Anthony, American Falls, Aberdeen, Atomic City, Idaho National Laboratory, Craters of the Moon, Fort Hall, Rockland, Arbon, Holbrook, Malta, Declo, Raft River, Rupert, Heyburn, Paul and Burley.
East Idaho's mountain areas will also face fierce wind conditions, with gusts reaching 55 mph on Emigration Summit and in the Bear River range and 45 mph in other highland areas, making for extremely hazardous driving conditions via the blowing and drifting snow.
"Gusty winds could make driving difficult, especially for high profile vehicles," forecasters warned. "Unsecured objects may be blown around."
The storm will pummel the region in two punishing rounds.
Round one begins Monday evening in the central mountains, including Sun Valley, Stanley and the Frank Church Wilderness, where four to eight inches of snow are expected below 7,500 feet and eight to 12 inches above that elevation between 8 p.m. Monday and 5 p.m. Tuesday. Galena Summit has a 40 percent chance of being buried under at least 10 inches.
Snow will spread to East Idaho's highlands around 11 p.m. Monday, hammering the mountains with two to six inches below 7,000 feet and six to 10 inches above that elevation. Monida Pass has a 60 percent chance of receiving 12 inches.
East Idaho's lowlands, including Pocatello, Chubbuck, Blackfoot, Idaho Falls, Ammon and Rexburg, could see an inch of snow during the first round.
"The hazardous conditions could impact the Tuesday morning and evening commutes," the weather service said.
A brief reprieve arrives late Tuesday morning through Tuesday afternoon before round two moves into East Idaho Tuesday evening.
The second round will deliver lighter snowfall to the central mountains — three to six inches — but similar or heavier amounts to East Idaho's highlands. The Emigration Summit area and Bear River Range will bear the brunt with another 10 to 14 inches of snow, pushing storm totals there to as much as 30 inches.
East Idaho's lowlands, including the Pocatello, Chubbuck, Blackfoot, Idaho Falls, Ammon and Rexburg areas, could see one to three inches of accumulating snow Tuesday night through Wednesday morning — enough to create treacherous roads during the Wednesday morning commute.
Wind gusts in East Idaho will remain breezy at 25 to 35 mph through Tuesday afternoon, ease overnight, then roar back Wednesday afternoon at the same intensity.
The heaviest snow across East Idaho should taper off by 5 a.m. Thursday, though light snow showers will linger on and off through Friday.
The National Weather Service is urging anyone who must travel to pack an extra flashlight, food and water in their vehicle in case of emergency. For the latest road conditions, call 511 or visit 511.idaho.gov.
The storm marks a dramatic change to a winter season that up until now has been drier and warmer than normal across East Idaho.