Good morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Forecast on Sunday, April 2nd at 7:00 a.m. This information is sponsored by Grizzly Outfitters and Gallatin County Sheriff Search and Rescue. This forecast does not apply to operating ski areas.
Since yesterday morning, near West Yellowstone and Cooke City received 10-11” of heavy new snow, and 3-4” fell near Bozeman and Big Sky. Wind has been out of the southwest-west at 15-30 mph with gusts of 40-85 mph. Temperatures are singles to teens F and will reach 20s F today. Wind will continue at 15-30 mph out of the west with gusts to 40 mph. Snow showers will deliver 3-5” near Cooke City and Taylor Fork with 1-3” near Big Sky and West Yellowstone, and maybe 1” near Bozeman by tomorrow morning.
Heavy new snow and strong wind are creating very dangerous avalanche conditions on wind-loaded slopes. Human-triggered and natural avalanches are likely where wind is drifting the new snow into thicker slabs and overloading buried weak layers. Avalanches breaking in the new and wind-drifted snow will be large enough to be potentially deadly, and very large avalanches could break several feet deep on weak layers that were buried months ago.
Since late February we have seen huge human-triggered and natural avalanches that broke deep in the snowpack. The most recent were just over a week ago near Cooke City, triggered by snowmobilers (Daisy Pass, Henderson Mtn.). Similar slides are likely today. On non-wind loaded slopes the likelihood is lower, but dangerous avalanches can be triggered on any slopes steeper than 30 degrees. Avoid riding across and underneath steep slopes. Avalanche danger is HIGH on wind-loaded slopes and CONSIDERABLE on non-wind loaded slopes.
The mountains near Bozeman and Big Sky received less snow, but plenty of wind over the last 24 hours. On wind-loaded slopes, human-triggered avalanches are likely. Fresh drifts of snow will be easy to trigger, and avalanches could break on weak layers buried below last week’s heavy snowfall or deeper on weak layers that were buried in January.
On Thursday in the Lone Lake Cirque near Big Sky resort, a snowboarder took a ride over huge cliffs in a slide that broke at least 2-4 feet deep (photo). On Friday, a fresh natural wind slab was seen on Cedar Mountain (photo), and in Portal Creek riders triggered a 2-3 ft deep avalanche from 100 ft away (details and photos). The slide in Portal Creek likely broke below last week’s snow on weak faceted snow that has remained unstable. Yesterday in the northern Bridger Range, skiers saw a recent very large natural avalanche that broke several feet deep and 500 feet wide (details and photos).
Plan to avoid steep wind-loaded slopes. Before traveling across any steep slopes carefully assess the snowpack for recent wind-loading and buried weak layers, and choose slopes with minimal hazards like trees or cliffs in the runout zone. The avalanche danger is CONSIDERABLE on wind-loaded slopes and MODERATE on non-wind loaded slopes.
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Heavy new snow and strong wind are creating very dangerous avalanche conditions on wind-loaded slopes. Human-triggered and natural avalanches are likely where wind is drifting the new snow into thicker slabs and overloading buried weak layers. Avalanches breaking in the new and wind-drifted snow will be large enough to be potentially deadly, and very large avalanches could break several feet deep on weak layers that were buried months ago. Avoid riding across and underneath slopes steeper than 30 degrees.
Hyalite Canyon road is closed for motorized use until May 16.