Frisby Avalanche Observation

Dug a pit on a North Aspect at treeline on Frisby today. Goal was to observe new storm snow interfaces and mid November rain crust. CTH1 Sudden drop down 118 on facets. ECT BRK with no propagation.

Group observed a slab avalanche. Visibility was obscured but we believe it was naturally triggered. We could not see any snowmobile/skier tracks. Crown varied in depth from 40-120 cm on the NE aspect at treeline, 1800m. It looked like it was triggered 12-24 hours ago. Group noted wind loading on NE aspects. Suspect weak layer was mid November rain crust with facets. We did not touch/feel the bed surface/weak layer first hand.