Bridger Range

Wind slabs can easily be triggered at upper elevations today. Also at upper elevations and at mid elevation northerly facing slopes is weak snow near the ground that may cause persistent slab avalanches. These larger slides haven’t happened since early December, but we know the potential exists just not exactly when it may happen. This layer generally doesn’t exist on mid elevation southerly facing slopes where you might find good powder in wind sheltered terrain.

Even though snowfall has stopped, there is tons of fresh snow that will be transported by increased SW winds today. Wind loading adds snow and weight up to 10 times faster than snowfall from the sky.

Snowfall has pummeled the Cooke City area where the avalanche danger is HIGH and an AVALANCHE WARNING continues today. In the last 6 days, snow containing 7 inches of water has fallen which is a huge load. Riders triggered a large wind slab avalanche yesterday on Henderson Mountain. With loading like this, avalanches of all types and sizes are very likely today, some breaking in recent storm layers, others breaking near the ground. Avoid all avalanche terrain and stay far away from avalanche runout zones.

Near Island Park & West Yellowstone as well as the southern Gallatin Range and the entire Madison Range (near Big Sky) - The avalanche danger is also HIGH at upper elevations where SW winds will transport all the fresh powder causing wind slab avalanches or much larger persistent slab avalanches over 3 feet deep breaking near the ground. See Ian’s video from Buck Ridge yesterday and Dave’s video from the Taylor Fk area on Sunday. 

Here’s the problem: I don’t think you’ll see any signs of instability like collapsing or shooting cracks. Layers of snow in the middle of the snowpack became very dense, cohesive, and supportable from very warm weather and hurricane force winds last week. These layers hide very weak, faceted snow lurking near the ground. Wind loading today could push that layer to it’s breaking point. The best option is to avoid avalanche terrain and ride slopes less than 30 degrees in steepness.

The northern Gallatin Range (Hyalite Canyon) has very similar conditions, but has received less snow (6 inches snow, 0.6 inches water in the last 48 hours). Wind loading today will make the danger CONSIDERABLE at upper elevations. At low elevations, minimal new snow means a minimal hazard. 

In the Bridger Range, the Bridger Bowl Ski Patrol easily triggered storm slab avalanches yesterday. A group ascending the Ramp just to the north wisely avoided avalanche terrain based on activity in the ski area. Today the danger will remain CONSIDERABLE at upper elevations where winds are the strongest and wind slabs can be triggered. Storm slabs should be much less reactive today. The question for the Bridger Range (on big wind loaded slopes at upper elevations like Saddle Peak), will weak facets near the ground produce large persistent slab avalnches? We haven’t seen avalanches on them yet, but we know that weak layer is there (Dave’s video from Dec 15). I’m not ready to trust them.