Partner fell at the top of a steep convex roll released a small storm slab. Carried for 50 ft but able to self arrest. Snow ran about ~200' vert. Moving at medium speed, not as slow as I have been seeing storm snow sluff moving the last few days. I had skied the roll minutes before, put some weighting cuts on the roll. Aspect was mostly west barely south. Guess it was about 38* but no mesure of slope angle. Snow was receiving solar warming. Partner was rattled so didn't take time to investigate the crown and weak layer that it broke on. Would think it is the interface between the most recent storm snow and the previous snow. I think the sun/warming had formed the new light snow into more of a slab. Was experiencing some short shooting cracks just before incident. Camera batteries dead so no pictures either.