Wind slabs could step down to deeper persistent weak layers.
Start with conservative terrain and gather information before committing to slopes.
Wind slabs may remain sensitive to human-triggering. Slabs could step down to deeper layers, resulting in larger than expected avalanches.
A crust / facet layer from mid-November is buried 60 to 100 cm deep. Several recent large to very large avalanches in the region have failed on this layer.
On Thursday, several size 2-2.5 explosive-triggered slabs occurred in the Duffey area. They were suspected of having stepped down to the mid-November persistent weak layer.
On Tuesday, a deep and large slab (size 2.5-3) was observed on Matier’s East Ridge. (See photo below) This slab was also suspected of having failed on the persistent weak layer.
Observations in the aea are very limited. Please consider sharing your observations on the MIN.
In the alpine, strong southerly winds scoured windward slopes, while building slabs in leeward and crossloaded terrain. A surface crust may be present up to 1800 m.
Several layers, including surface hoar, facets, and a thin crust, can be found 40 to 65 cm below the surface.
A crust with facets, formed in early November, is buried 50 to 100 cm at alpine and treeline elevations. This persistent weak layer has been the failure plane of several recent large avalanches in the region.
Snowpack height averages around 100 cm at treeline and decreases rapidly below 1500 m.
Friday Night
Cloudy. 1 to 5 cm of snow at treeline. 30 km/h southwest ridgetop wind. Treeline temperature -3 °C. Freezing level 1000 m.
Saturday
Mostly cloudy. 1 to 2 mm of precipitation as snow or rain at treeline. 40 km/h southwest ridgetop wind. Treeline temperature 1 °C. Freezing level rising to 2200 m.
Sunday
Mostly cloudy. 10 to 25 mm of precipitation as snow or rain at treeline. 40 km/h southwest ridgetop wind. Treeline temperature 0 °C. Freezing level 1700 m.
Monday
Mostly cloudy. 15 to 30 mm of rain at treeline. 40 km/h south ridgetop wind. Treeline temperature 2 °C. Freezing level 2200 m.
More details can be found in the Mountain Weather Forecast.
