From interaction at the gas station:
“We were riding out from Island Park. We saw dramatic, collapses, and shooting cracks. I side-hilled a small slope and triggered it 1.5 to 2 feet deep. I have never seen such unstable snow.”
The avalanche likely failed on a layer of surface hoar widespread in the Lionhead and Island Park areas. The avalanche buried part of the groomed road that crosses below this slope.