Continued snowfall and wind are causing dangerous avalanche conditions to persist. Human-triggered avalanches are very likely and natural avalanches continue on wind-loaded lee slopes.
Uncertainty is best managed through conservative terrain choices at this time.
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.
Overnight flurries continue to build on 50 - 100 cm of storm snow. In all exposed areas, new snow and strong southwesterly winds have built reactive storm slabs. The snowpack has not adjusted to this heavy new load and is 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.
In the Pine Pass area, heavy snowfall caused a natural avalanche cycle that started on Thursday and continued through the weekend. Reports from Thursday indicate storm slabs were very reactive to snowmobile traffic, producing many size 1 to 1.5 storm slab avalanches that propagated widely.
On Saturday, explosives control produced several size 2 to 3 wind slab avalanches in cross-loaded alpine start zones.
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 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.
See more on the potential of triggering deeper weak layers in our latest Forecasters' Blog.
Stormy weather over the past week has brought 50 to 100 cm of new snow to the region. Warm windy weather is causing storm snow to settle into reactive slabs. 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.
Monday Night
Cloudy with scattered flurries, 8-15 cm accumulation. Localized areas, particularly around Kakwa, may see higher accumulations with up to 25 cm. Alpine temperatures low of -3 C. Ridge wind southwest 60 km/h, 70-80 km/h over Kakwa. Freezing level slowly lower to 1000 m overnight.
Tuesday
Mix of sun and cloud with isolated flurries, 2-5 cm accumulation. Alpine temperatures drop to -6 C. Ridge wind southwest 40-60 km/h. Freezing level 1200 meters.
Wednesday
Mainly cloudy with sunny periods and isolated flurries, 2-5 cm accumulation. Alpine temperatures rise to -7 C. Ridge wind southwest 60 km/h easing in the afternoon. Freezing level 1000 meters.
Thursday
Mainly sunny with cloud increasing in the afternoon and isolated flurries, 2-10 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.
More details can be found in the Mountain Weather Forecast.
