Bridger Range

Buckle up, all of a sudden, avalanche season is in full swing. Avalanches are breaking under the new snow on weak layers in the pre-Thanksgiving old snow and could also break within the new snow itself (with or without wind drifting). Enough new snow has piled up that all steep slopes are suspect. Avoid any slopes steeper than 30 degrees that have a cohesive slab thicker than 10”.

During the storm on Thursday night, a large natural avalanche broke on The Fin, on Mt. Republic, near Cooke City (photo). This slide broke 1000+ ft wide, across the whole face. Skiers also triggered a slide in the Midways in the Bridger Bowl Ski Area (which is not yet operating or conducting avalanche mitigation) and were caught and carried approximately 100 ft  (observation and photos). Both of these Persistent Slab avalanches broke 1.5-2 ft deep on weak layers that developed in the snow that fell before Thanksgiving. A small natural avalanche also broke down to old snow along the Beehive-Middle Basin ridgeline, near Big Sky (photo). 

Any slope that held onto snow through the pre-Thanksgiving dry spell is suspect. Dig down to look for old snow and check its stability before committing to any steep slope. Higher elevation and shadier slopes are more likely to hold this old snow.

Last night’s new snow fell at warmer temperatures and is denser than the snow from the day before. This means the new snow is “upside down” and in areas with more than 10” of recent snow you could trigger dangerous Storm Slab avalanches even on non-wind-loaded slopes. This doesn’t mean you should forget about wind loading. Winds have been howling and wind-loaded slopes will have substantially thicker, denser, slabs and be even touchier and more dangerous. This video of a skier-triggered slide from last week in the northern Bridgers is a good reminder of the power of a relatively small slide and that it only takes a couple inches of new snow combined with wind drifting to create a dangerous slab (video). Avoid slopes steeper than 30 degrees that have a cohesive slab thicker than 10”, whether that slab formed from windloading or storm snow density changes.

The concerns are the same across the advisory area, but with more new snow and more on the way today, avalanches of all sorts will be larger, easier to trigger, and more widespread in the Bridger, N. Madison and N. Gallatin Ranges and Cooke City area. The avalanche danger is CONSIDERABLE in these areas.

With less new snow, concerns are mostly limited to wind-loaded slopes and the avalanche danger is MODERATE in the S. Madison and S. Gallatin Ranges, as well as the Lionhead and Island Park areas.