Intended to ride Lyle glacier. Due to helicopter traffic, was forced onto steeper and wind affected east face of maple pass. 2pm, third rider in party triggered a slab avalanche approximately 3’ deep and 200’ wide running approx 400.’ Third rider was swept the entire way. Resurfaced as debris fanned out, unharmed. 1st and 2nd rider posted up in small treed island further away were affected by snow impact including partial burial. 4th in party watched from above maintaining safe distance. No injuries, safe ride out.
Lessons: remote localized snowpack variances necessitate conservative route choice. Include a large margin for safety of onlookers- close enough to help, far enough for safety. Avalanche was larger and thus traveled much faster and farther than expected.