Persistent Slab Avalanche on Castle Peak

An unintentional cornice fall released a large persistent slab avalanche on the north side of Castle Peak today at approximately 11am.  The cornice piece that was collapsed by an individual walking along the ridge was the size of a small car.  The crown was mostly in the 4' to 6' range with some areas up to 8' deep.  The avalanche was 200' wide and ran 800' full path down to the flats.  Avalanche size was D2.5 pushing D3. There were ski, snowboard, and snowmobile tracks made today all over the north side Castle Peak on this slope and on the immediately adjacent slopes. The slope that avalanched held several tracks prior to the avalanche event.

The location of the crown prevented a safe and full investigation.  The bed surface of the avalanche appeared to be old snow with a thin crust on the surface.  The failure layer is thought to be the facet/crust combo that was buried before the 1/5-1/7 storm cycle.   We were unable to get down into the crown or onto the bed surface, but by throwing rocks and snow we could determine that the bed surface was a crust which would indicate the facet/crust combo that was deeply buried by the 1/5-1/7 storm.