Cooke City

Winds yesterday have been the main factor in creating dangerous avalanche conditions, and they spared few slopes. Any wind loaded or wind affected slope is likely to produce an avalanche 1-2 feet deep. Sheltered terrain has a widespread weak layer of facets under the new snow, especially on more northerly facing slopes where persistent slab avalanches are possible.

Despite varied snowfall amounts, strong winds drifted snow in all areas producing natural and human triggered avalanches:

• Dave and I rolled up just after a rider remotely triggered a slide (not caught) off the north side of Reas Peak near Island Park. We triggered a small wind slab and spotted about 5 others.
• A rider near West Yellowstone under Lionhead Ridge triggered a slide from below a steep slope and was caught but not injured.
• In Hyalite Canyon, a skier spotted a natural avalanche 1-2 feet deep and ~200 ft wide near Maid of the Mist Mtn.
• In the backcountry terrain near Big Sky in Lone Lake Cirque a large natural avalanche over 300 feet wide happened. 
• Just south of Cooke City, Alex experienced shooting cracks on wind loaded slopes.
• On Monday, north of Cooke City near Wolverine Peak, guides spotted one natural avalanche and triggered another. 
• On Monday, a natural avalanche just north of Bridger Bowl was spotted.
• On Monday, along Buck Ridge just south of Big Sky a wind slab resting on facets on a small slope broke over a surprisingly far distance (video).

Any slope touched by yesterday’s howling winds (which is almost every open slope) will likely produce an avalanche 1-2 feet deep today. A wide spread layer of facets underneath the recent snow and wind drifted snow will allow avalanches to break over much wider areas and be triggered remotely. Snow falling today may camouflage visual signs of wind effect on slopes.

Where it gets tricky is on the few sheltered slopes that were untouched by yesterday’s winds. Persistent slab avalanches can be triggered on these sheltered slopes mostly in places that received the most snow near West Yellowstone, Island Park, Southern Gallatin and Madison Ranges. Popular areas like Bacon Rind and Trapper Creek near Hebgen Lake will be especially sensitive as they produced slides (like this one last week) and collapsing/cracking prior this snowfall. 

Today throughout the forecast area the avalanche danger is CONSIDERABLE. It’s a great time to get out and enjoy the fresh snow, but these are dangerous avalanche conditions requiring careful route finding and terrain selection. There are almost no steep slopes I’d feel comfortable riding today, and the safest option is to choose slopes less than 30 degrees in steepness with nothing steep above you.