Quartz Backcountry Ski cut Avalanche

Ski cut top of slope before entering. Planar results on new storm snow that stepped down 40-60cm to December17 interface. Avalanche ran about half path and stopped on bench in trees. Line was previously ridden 2 weeks ago with good stability. Once storm slab failed the avalanche stepped down to layer beneath that which was previously skied on. (December 17 interface). Group was able to ride debris and trees and exit safely. Instabilities and cracking noticed throughout tree riding for remainder of run.