Widespread Wind and Storm Slab Activity on Andesite

In near and above treeline terrain exposed to wind-loading, ski cuts and kicks in lower angle terrain near or above test slopes triggered widespread wind slab avalanches on Andesite Peak today. Cornices above wind-loaded slopes also easily broke from small ski kicks. The smaller pieces of cornices triggered wind slab avalanches on the slopes below. The wind slab avalanches propagated across entire slopes and wrapped around corners. One wind slab avalanche propagated across a 300 to 400 ft. slope from a ski kick on a nearby low angle slope. Most of these wind slabs measured 8 to 16 inches in depth and failed on a weakness within the upper part of the storm snow, but the largest of them did step down to a lower storm snow weakness just after the primary slide reached the bottom of the slope. This secondary release had a 3 to 4 ft. crown and likely failed on a lower storm snow weakness. We did not investigate the bed surface due to the amount of hangfire remaining on the slope, but snowpit tests on the side of a nearby test slope revealed a weakness within the storm snow at about the same depth that produced unstable results (ECTP) even though a smaller avalanche had already occurred on the test slope.

In more sheltered below treeline terrain, widespread skier triggered cracking occurred. Ski cuts on test slopes in below treeline terrain caused some slopes to fracture and crack but as they slide downhill the softer storm slabs quickly broke apart. Most of these failed on a weakness about 6 to 10 inches down in the most recent storm snow. Ski cuts on one lower angle test slope did produce shooting cracks that propogated about 150 ft away and caused a storm slab avalanche on a connected steeper slope. This storm slab started as a 6 to 8 inch crown and then stepped down to a lower storm snow weakness about 18 to 24 inches below the surface similar to the wind slab mentioned above. As more snow accumulated during the day signs of storm slab instability became more widespread. A skier triggered whumpf also occurred on a low angle WSW aspect as a weakness within the storm snow collapsed. Ski cuts on steep sheltered slopes also triggered loose dry sluffs. 

Snowfall continued throughout the tour with snowfall rates of 2 to 3 inches per hour. In exposed near and above treeline terrain wind-loading also continued throughout the tour.