Northern Gallatin Range

Weak snow near the base of the snowpack may result in human-triggered avalanches, especially at higher elevations. Follow safe travel practices, select lower-consequence terrain that was sheltered from recent wind-loading, and evaluate the snowpack for instability from buried weak layers using extended column tests.

Glance at the avalanche dangers on the map, and you’ll see a lot of yellow, or MODERATE danger, but dig into the details, and there are some critical differences.

The southern portion of the forecast area, including the S. Madison and S. Gallatin Ranges, and the Lionhead, Island Park, and Cooke City areas, has only gone one day without a large, tree-snapping, persistent slab avalanche. On Monday, snowmobilers triggered a large slide north of Cooke City; they escaped (details and media), and an avalanche broke widely across Airplane Bowl in the Lionhead area. For weeks straight, avalanches regularly broke 300 feet to a quarter-mile wide and 2 to 6 feet deep (avalanche activity list). While persistent slab activity has focused on the south half of the advisory area, recent slides on Buck Ridge and Lone Lake Cirque in the Northern Madison Range demonstrate that the problem extends further north, but with smaller avalanche size and lower frequency.

Slabs of wind-drifted snow are stabilizing with time and warm temperatures. Watch for isolated instability indicated by shooting cracks and note that persistent slab avalanches are most likely on slopes with the added weight of wind-loaded snow.

While the likelihood of triggering an avalanche has come down in the Southern Madison and Southern Gallatin Ranges and the Cooke City, Island Park, and Lionhead areas, the consequences of getting caught have not (video). The snowpack is generally too deep for a stability test to provide reliable information and avoiding slopes steeper than 30 degrees remains prudent. If your choices lead to steeper areas, select smaller, less steep slopes that are sheltered from wind loading and free of terrain traps. Carry and practice with rescue gear, watch your partners closely, and do not expose more than one person to the avalanche hazard at a time. The danger is rated MODERATE at all elevations.

At upper-elevations in the Bridger Range, and middle- and upper-elevations in the Northern Madison and Northern Gallatin Ranges, the avalanche danger is MODERATE. Follow safe travel practices, select lower-consequence terrain, and evaluate the snowpack for instability from buried weak layers using an extended column test. In the Bridger Range, temperatures in the 40s F may lead to small, wet loose avalanches. These will be relatively harmless to skiers and riders except in steep, confined terrain.

Weak layers are gaining strength at lower- and middle-elevations in the Bridger Range, as well as at low elevations in the Northern Gallatin and Northern Madison Ranges, where the danger is currently LOW, and avalanches are unlikely (video).