Island Park

Dangerous persistent slab avalanches are likely, and wind slab avalanches are possible. Assessment of the persistent slab problem is tricky, so careful terrain selection is essential. Slopes steeper than 30 degrees should be avoided, as well as flatter terrain directly below steep slopes.

On Saturday 4-11” of low density snow fell, and yesterday moderate to strong winds drifted that snow into thicker slabs. These wind slabs might still be unstable today, and can crack and avalanche under the weight of a person.

In the Bridger Range, steady winds blew at all elevations yesterday, and you can expect to find fresh drifts on mid-slope rollovers or other less commonly wind-loaded features, as well as near upper elevation ridgelines. 

Elsewhere, gusty winds were mostly confined to higher ridgelines, so fresh wind slabs are less widespread. However, a more serious persistent slab avalanche problem exists deep in the snowpack. 

Weak layers near the bottom of the snowpack have been causing persistent slab avalanches large enough to easily bury or injure a person (Taylor Fork avalanches). These can be 2-6 feet deep in areas with shallower snow depths, and up to 8-15 feet in deeper areas. Where more snow has fallen over the last couple weeks, like near Cooke City and the southern Madison Range, some slides were destructive enough to snap mature trees (avalanche on Scotch Bonnet earlier in the week). Dangerous persistent slab avalanches are more likely in the southern half of our forecast area, but remain possible elsewhere (avalanche on Buck Ridge, Lone Lake Cirque), and deserve careful consideration if you plan to cross on or underneath steep slopes. 

Assessment of the persistent slab problem is tricky, so careful terrain selection is essential. Yesterday Dave rode in the southern Madison Range and witnessed a couple recent big avalanches (Dave’s obs. from Tepee). For areas that received more snow over the last couple weeks, he highlighted the best strategy is to avoid crossing on or underneath slopes steeper than 30 degrees (Dave’s video from Tepee).

Near Cooke City, West Yellowstone, Island Park, and in the Southern Madison and Southern Gallatin Ranges avalanche danger is CONSIDERABLE and slopes steeper than 30 degrees should be avoided. 

In the Bridger Range, Northern Madison Range and Northern Gallatin Range the avalanche danger is MODERATE. Watch for cracking on the snow surface as a sign fresh drifts could break. If you plan to cross steep slopes, carefully assess the snowpack for buried weak layers, and choose smaller slopes without terrain traps like trees, gullies or cliffs in order to minimize potential size and consequences of an avalanche.