Video clips of avalanche incidents which is available on-line. Also check archives of local television news stories (stations in Western states and Provinces) regarding avalanche incidents and fatalities.
Sawtooth National Forest Avalanche Center (Idaho)
Gallatin National Forest Avalanche Center (Montana)
Northwest Avalanche Center
Utah Avalanche Center
Stability tests, non-standard – https://utahavalanchecenter.org/education
‘A Dozen More Turns’
A powerful documentary; while ski-based, the backcountry decision-making lessons are also pertinent to snowmobiling.