Several weak layers are active in the snowpack. Successfully managing their complexity is less about picking out the most problematic layer and more about sticking to diligent group management and more conservative terrain while the snowpack strengthens.
Several different weak layers can be found in the snowpack, they are now deeply buried, and they have produced large avalanches as recently as Monday. It remains prudent to assume these layers are present, reactive to human triggers, and capable of forming very large, destructive avalanches.
Wednesday night: Clear periods. Light variable winds.
Thursday: A mix of sun and cloud with cloud increasing over the day. Light to moderate southwest winds increasing over the day. Alpine high temperatures around -8.
Friday: Mainly cloudy. Light to moderate southwest winds shifting northwest. Alpine high temperatures around -8.
Saturday: Mainly cloudy. Light to moderate southwest winds. Alpine high temperatures around -10.
Several more large persistent slabs were triggered with explosives control in the Nelson area on Monday. These slabs featured crown depths of 15-120 cm, giving some evidence of wind loading. These avalanches are suspected to have released on our early November facet/crust layer, which exists below two other persistent weak layers of concern.
A widespread avalanche cycle occurred on Saturday, with observations of large artificially triggered avalanches continuing into Sunday. Many of these recent avalanches released within the storm snow, and large avalanches weren observed on all aspects, generally above 2000 m. Numerous other large to very large avalanches were also triggered by explosives on the late-November layer described in our Snowpack Summary.
The stormy period that ended early this week saw around 70 to 100 cm of snow deposited in the region, initially accompanied by strong west wind. This snow has loaded multiple weak layers, including:
There is uncertainty on which of these layers will emerge as our primary persistent slab problem. However, given extensive recent avalanche activity during and in the days after the storm, it remains prudent to make terrain decisions with the understanding that any one of these deeply buried layers could produce large and destructive avalanches with a human trigger.
