Avalanche Forecast
Issued: Dec 19th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
zryan,
Avalanche Canada
Conditions are more complicated than meets the eye. Wind-drifted snow and buried weak layers warrant a cautious approach and diligent decision making.
Summary
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
Sunday Overnight: High pressure will continue to strengthen into the evening. Light northerly winds and clear skies. Temperatures dropping to -15 C in the alpine.Â
Monday: Clear skies with alpine temperatures around -15 C. Light southwest winds at ridgetop.
Tuesday: Mainly clear with moderate west winds at ridgetop. Temperatures rising with an alpine high of -8 C.Â
Wednesday: Mainly cloudy with flurries, 3-15 cm accumulation. Moderate to strong southwest winds at ridgetop. Alpine temperatures around -8 C.
Avalanche Summary
On Sunday, operators reported ski cutting and explosive storm slab results to size 1 in the alpine and treeline.
On Saturday, operators reported reactive wind slabs developing throughout the day.
On Friday, operators in the eastern Purcells triggered several size 2-2.5 deep persistent avalanche with explosives on N and NW aspects in the alpine.
Snowpack Summary
Saturday's storm brought 20-50cm of new snow to the region. This new snow was accompanied by moderate to strong southwest winds which have formed wind slabs in the alpine and treeline.
Below this new snow, 40-60cm of consolidated snow sits over a substantial crust that formed in early December. This crust is 10-30 cm thick and can be found down 60-120 cm. It is present across aspects below 2300m. A thin layer of weak facets (sugary snow) can found above this crust that has demonstrated reactivity in snowpack tests. This problem is particularly hard to predict and tricky to manage. For this reason wide, conservative terrain margins and disciplined backcountry travel techniques will be very important. Get more details and photos in our forecaster blog.Â
A late October facet/crust layer of concern sits at the bottom of the snowpack above 1900m. Although this layer has been trending less reactive, it remains on our radar.
The snowpack depth at treeline is around 115-200 cm. The deepest snowpack can be found near the Bugaboos.Â
Terrain and Travel
- Be careful as you transition into wind affected terrain.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
- Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.
Problems
Wind Slabs
In wind-drifted areas, wind slabs in the alpine and treeline may remain reactive to human triggering. If the winds pick up today, there is a lot of snow available for transport which will create fresh, reactive wind slabs.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A layer of weak facets (sugary snow) can be found down 50-100 cm over a crust that formed in early December. This layer is starting to produce avalanches across the province and as we assess the additional load on this layer from the storm, it will be critical to employ good travel habits and diligent decision making.
At the base of the snowpack above 2200 m, a layer of depth hoar lingers. Avalanches-in-motion have the potential to step down to this layer.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 20th, 2021 4:00PM
