Northern Gallatin Range

Strong winds on Tuesday ripped across many slopes forming wind slabs and also extra loading to make triggering a persistent slab avalanche more likely mostly at upper elevations. Conditions are tricky. The easiest option is to go to slopes less than 30 degrees in steepness that aren’t steep enough to slide.

The Island Park and West Yellowstone/Lionhead areas and the Southern Madison and Gallatin Ranges (including Taylor Fork, Cabin Creek, and Teepee areas) have tons of fresh powder, great skiing and riding, and also a widespread weak layer buried 2-3’ deep making dangerous avalanche conditions.

Ian’s observations (video & ob) yesterday on Lionhead near West Yellowstone sum up conditions really well:

• If he hadn’t been looking for recent avalanches (which he did see), the snowpack gave him no signs of instability like collapsing or shooting cracks. This can lead you to believe conditions are stable when they aren’t.
• There were many storm slab and wind slab avalanches, some hundreds of feet wide.
• When he went to check out a recent shallow avalanche, he triggered a much deeper persistent slab avalanche about 2’ deep on sugary facets from the January dry spell on the same slope.
• A rider was partially buried but uninjured in a slide in that area on Tuesday.

This mirrors what Dave and I found on Sawtell and Reas Peak near Island Park on Tuesday when a rider triggered an avalanche from low on a slope (complete ob with the avalanches we found, and video). The snowpack was not “talking to us” to let us know of dangerous avalanche conditions.

In Island Park and West Yellowstone/LIonhead areas as well as the Southern Madison and Gallatin Ranges, the avalanche danger is CONSIDERABLE. It will take a while for things to settle down.  The best option for now is to ride slopes less than 30 degrees in steepness that aren’t steep enough to slide and avoid being under steeper slopes.

In other parts of the forecast area near Big Sky, Bozeman, and Cooke City, the skiing and riding are also great with fresh, cold snow. These areas also have a widespread weak layer from the January dry spell that is creating dangerous avalanche conditions.

A big persistent slab avalanche  in the Lone Lake Cirque on Lone Mountain at Big Sky is a great example of what’s possible. These avalanches will be most likely at higher elevations where strong south winds on Tuesday left few slopes untouched creating both wind slabs and additional loading to make the persistent slab problem more sensitive. 

Just south of Cooke City on Tuesday, Alex experienced shooting cracks on facets now buried about foot deep. In that area today, the danger is CONSIDERABLE at mid and upper elevations mostly on wind loaded slopes, but that wind effect will be camouflaged by 4” of snow that fell yesterday.

For today in the Northern Madison and Gallatin Ranges and the Bridger Range, the danger is CONSIDERABLE on previously wind loaded slopes at higher elevations. To decrease your odds of triggering a slide aim for wind sheltered slopes at mid and lower elevations. Or to totally remove the risk of avalanches opt for great riding on slopes less than 30 degrees in steepness.