Good morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Forecast on Monday, March 27th at 7:00 a.m. This information is sponsored by Grizzly Outfitters and Cooke City Super 8/Bearclaw Bob’s. This forecast does not apply to operating ski areas.
Near Bozeman and Big Sky received 4-8” of new snow since yesterday morning, and 1-2” fell near West Yellowstone and Cooke City. Temperatures are singles to teens F. Wind has been out of the northwest-northeast at 5-10 mph with gusts of 15-30 mph. Today temperatures will reach low 20s F with westerly wind at 5-15 mph. Snow showers tapered off overnight, and today near Cooke City could get 1” of snow with no snow expected elsewhere.
Human-triggered avalanches are likely and natural avalanches are possible where new snow is drifted into denser slabs. Since Friday evening the mountains near Bozeman, Big Sky and West Yellowstone received 12-28” of snow equal to 0.9-1.8” of snow water equivalent (SWE), and we heard reports of 40” of low density snow in spots. Yesterday in the northern Gallatin Range, riders reported avalanches that broke up to a foot deep in the new snow (photos and details), and skiers on Mt Ellis saw a recent skier triggered slide that broke up to 3 feet deep which was relatively large on a very small slope. This slide appeared to have partially buried a skier who self-extricated (details and photos).
Avalanches breaking within the new and wind-drifted snow are most likely, but larger slides breaking several feet deep on old persistent weak layers are possible and have large consequences. A slide that broke 8-10 ft deep earlier this week on Elephant Mtn. in Hyalite is an example of huge avalanches that could be triggered or break naturally today (details and photos). See our avalanche activity list and recent videos for more examples of recent big slides.
You can reduce the risk of being caught in any type of avalanche by avoiding wind-loaded slopes steeper than 30 degrees. Choose small, simple terrain that is not exposed to trees, cliffs or confined gullies. Before traveling across or below any steep slope, carefully assess stability of the new snow and consider the possibility of deeper buried weak layers. If you suspect either could cause an avalanche, stick to slopes less than 30 degrees altogether. Avalanche danger is CONSIDERABLE on wind-loaded slopes and MODERATE on non-wind loaded slopes.
In the mountains near Cooke City the main concern is triggering avalanches that break several feet deep on weak layers that were buried two months ago. On Thursday near Daisy Pass a snowmobiler triggered avalanche broke 4 feet deep, caught two riders, and one of them suffered a broken femur (details and photos, video). Additionally, a person can trigger avalanches of recent wind-drifted snow. If you plan to travel on or below steep slopes, choose smaller slopes that have not been wind-loaded and do not have large consequences such as trees, gullies or cliffs below. See Dave’s video from yesterday in Cooke City for tips about terrain selection. Human-triggered avalanches are possible and the avalanche danger is MODERATE.
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Human-triggered avalanches are likely and natural avalanches are possible where new snow is drifted into denser slabs. Larger slides several feet deep on old weak layers are possible. Avoid wind-loaded slopes steeper than 30 degrees. Choose small, simple terrain that is not exposed to trees, cliffs or confined gullies. If you suspect buried weak layers or recent snow could cause an avalanche, stick to slopes less than 30 degrees altogether.
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On Wednesday, March 22nd, a snowmobiler was killed in an avalanche in central Idaho. This brings the total number of avalanche fatalities in March to 8 people across the U.S. More info on each event is available at the Avalanche.org Accidents Page.