Steep Creek basin

on a wsw facing slope we triggered a size 2 avalanche. One skier caught and paritially buried with airbag deployment. We were in steep creek basin today march 29th and the slide happened at 1400. we saw absolutely no signs of instability's on the aspect we were riding and It had been previously been skied. the slide ran the nearly full length of the path, caught the skier and took them to the bottom. The slide was triggered above the skier by another member of the group. The crown was 15-20cm thick and 100m in length. the snow was wind pressed in spots but otherwise felt ok. Did not go back up to look at what surface slid or what it slid on. We think it was the small wind skin sliding on the March​ 21 layer