Professional Observation

Observation Details

Signs of Unstable Snow

Key Points

My AIARE L1 field group today took me on a tour around the North end of the Sherwin Ridge, in order to view start zones and natural avalanche activity in complex terrain, to sample a variety of aspects in the BTL elevation and to look for isolated wind slabs that may exist on specific terrain features at this elevation.

• Wind effect was windspread, in normally sheltered treed glades there was a noticeable zipper crust. Trees remained coated in a heavy snow/ice shellac, evidence of how wet the storm came in yesterday in spite of the strong and extreme winds over the past 24 hrs.
• Most ridge top start zones along Sherwin Ridge from Mammoth Rock Bowl to the Fingers had had crown lines, Natural trigger, Size D2-R2/3. Other steep panels below the Mineshaft and wrapping aorund the ridge also had run naturally.
• Panorama Dome NE was heavily wind affected down into the trees, with the upper slope being stripped down to water ice in some spots. We used a steep (38 deg) test slope and intentionally triggered a Size 1 wind slab that cracked 20+ feet off my ski tips. We performed a profile adjacent to the crown here and identified the 1F+ wind slab (CT11 SP and ECTP down 22cm on PPs. With an HS of 220cm at this site we could feel the facets by probing but were not motivated to dig down far enough to look at them in our pit.
• Overall a great day out with some soft turns in sheltered trees with plenty to look at and consider on our tour day.
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