I visited the crown of the avalanche in Nellie that was skier-triggered on Wednesday, adjacent to the Telluride Ski Resort. Last night's modest snowfall of 2-3 inches has already been blown by the wind and filled in much of the crown. After some digging around, I found that the crown ranged from around 40 to 80cm thick in the upper start zone, which released in deeper wind-drifted snow. The avalanche released below an old wind slab that was buried by the President's Day weekend snowfall. This knife-hard wind slab sat above a 5cm-thick layer of fist-minus facets (~2mm in size) with another knife-hard wind slab below it. This structure formed the textbook slab-facet sandwich, with the top wind slab collapsing and crushing the weak layer and sliding on the hard wind slab below. The bed surface of the avalanche was that firm old wind slab, which required hard front-pointing in ski boots to maintain purchase. At the crown where I dug, the old wind slab that fractured was about 8cm thick and knife hard, but the thickness of that layer varied. It's likely the skier found a thinner part of this hard slab and that's where the collapse occurred and crack initiated. With a relatively thin hard slab over a well developed persistent weak layer, the crack propagated far upslope from the skier's trigger point.

Upper Bear Creek

Nellie

Avalanche previously coded in this observation: https://avalanche.state.co.us/report/dc50c2d3-a4e6-4bfb-987e-3255146d4fa9