Continued snowfall and wind have created dangerous avalanche conditions, especially around wind-loaded slopes. Sheltered terrain will likely offer the best and safest riding.
Uncertainty is best managed through conservative terrain choices at this time.
Recent large persistent slab avalanche observations are strong evidence that these layers are still an active concern in this region. Numerous problematic weak layers exist in the top meter of the snowpack. Be cautious around steep openings within and near treeline elevations as active loading continues.
As storm snow continues to accumulate the snowpack is struggling to adjust to the heavy load from this week. In all exposed areas, new snow and strong southwesterly winds have built deep pockets in less that remain reactive to natural and human triggers.
If triggered storm slab avalanches may step-down to deeper weak layers and initiate large and destructive avalanches.
A layer of large and weak facets sits near the base of the snowpack. This layer is most prominent in upper treeline and lower alpine elevations. Storm 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.
On Monday, a natural wind slab avalanche, size 2 was observed on a northerly aspect at 1900 m.
On Sunday, three very large natural avalanches were observed up to size 4. Two were size 3 persistent slab avalanches on steep north-facing aspects with 750 m wide crowns. A size 3.5-4 deep persistent slab avalanche was also observed. It is suspected this avalanche failed in depth hoar at the base of the snowpack.
On Saturday, explosives control produced several size 2 to 3 wind slab avalanches in cross-loaded alpine start zones.
See more on the potential of triggering deeper weak layers in our latest Forecasters' Blog.
An additional 10 cm of snowfall throughout the region, 23 cm in Kakwa, brings storm snow totals to 60-110 cm. The storm snow sits on previously wind-affected surfaces. 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 and upper treeline terrain.
Tuesday Night
Mainly cloudy with isolated flurries, 5-10 cm accumulation. Alpine temperatures drop to -10 C. Ridge wind southwest 40-60 km/h. Freezing levels fall to valley bottom.
Wednesday
Mainly cloudy with isolated flurries, 2-5 cm accumulation. Alpine temperatures -10 C. Light west ridge wind westerly increase to 40-50 km/h in the evening. Freezing level 800 meters.
Thursday
Partly cloudy with isolated flurries, 5-10 cm accumulation. Alpine temperatures rise to -3 C. Moderate ridge wind from the southwest picks up to 50-70 km/h in the evening. Freezing level 1500 meters.
Friday
Partly cloudy with isolated flurries, 5 cm accumulation. Alpine temperatures rise to -2 C. Ridge wind southwest 40-60 km/h. Freezing level 1200 meters.
More details can be found in the Mountain Weather Forecast.
