Reactive wind slabs may exist in wind-loaded terrain, but our primary concern rests with the potential for large deep persistent slab avalanches.
Conservative, low-consequence terrain selection continues to be your best defence.
Recent storm snow and ongoing strong southwesterly winds are creating wind slabs in lee areas in the alpine and treeline. These slabs may remain reactive to human-triggering and have the potential to step down to deeply buried weak layers, resulting in large and consequential avalanches.
A layer of large and weak facets sits near the base of the snowpack. This layer is most prominent in upper treeline and alpine elevations. Wind slab avalanches could step down to this layer initiating very large avalanches. Riders are most likely to trigger an avalanche on this layer in steep, shallow terrain.
No new avalanches have been reported, but field information is very limited in this region.
We suspect recent storm snow and wind have created wind slabs in the alpine and treeline that may remain reactive to human triggering.
Our greatest concern lies with the potential for large natural and human-triggered deep persistent slabs. Your best defence is to stay diligent in choosing low-consequence terrain away from overhead exposure. See more on the potential of triggering deeper weak layers in our latest Forecasters' Blog.
Stormy weather over the past week has brought 20 cm of new snow to the region. This new snow was accompanied by strong southerly winds that have stripped exposed windward areas and deposited pockets of wind slabs in lee areas. The recent storm snow sits on previously wind-affected snow. Below this, a melt-freeze crust is found on sun-exposed slopes and everywhere below 1600 m.
Several crust/facet/surface hoar layers exist in the upper and middle portions of the snowpack. The most concerning persistent weak layer is at the base of the snowpack from large and weak facets formed in November. This layer is widespread and most likely problematic in steep, rocky alpine terrain.
In general, the snowpack is weak and shallow in this area with an average snowpack depth of 100 cm at treeline.
Sunday Night
Mainly cloudy with clear periods and isolated flurries, trace accumulation. Alpine temperatures reach a low of -6 C. Ridge wind westerly 30-50 km/h. Freezing levels fell from 1500 m to 500 m.
Monday
A mix of sun and cloud with isolated flurries in the afternoon, 2-5 cm accumulation. Alpine temperatures rise to -4 C. Ridge wind southwest 40-60 km/h. Freezing level rises to 1500 meters.
Tuesday
A mix of sun and cloud with isolated flurries, trace accumulation. Alpine temperatures drop to -6 C. Ridge wind west 10-30 km/h. Freezing level drops to 1000 meters.
Wednesday
A mix of sun and cloud with isolated flurries, trace accumulation. Alpine temperatures rise to -7 C. Ridge wind southwest 40-60 km/h. Freezing level rises to 800 meters.
More details can be found in the Mountain Weather Forecast.
