Avalanche Forecast
Issued: Dec 12th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Storm Slabs.
lbaker,
Avalanche Canada
Numerous persistent slab avalanches caught both professionals and recreationalist off guard over the last few days. Use extra caution at treeline where triggering a persistent slab is more likely.
Read our featured blog on understanding how to manage a persistent slab problem when traveling in the backcountry.
Summary
Confidence
Avalanche Summary
On Sunday numerous surprise human-triggered persistent slab avalanches were reported between 2200 and 1700 m. The spookiest reports on this layer are of a skier remote avalanche, size 3, at Kokanee Glacier and a skier sympathetic avalanche, size 2.5 in the Kaslo region. These avalanches either failed on the November weak layers or 'stepped down' from a smaller avalanches onto these deeper instabilities.
Storm slabs continued to be reactive during explovie control to size 1.5.
Almost every report from professional and recreational backcountry users notes signs of instability: whumpfing and shooting cracks.
Snowpack Summary
With warm temperatures storm snow has settled into a 20 - 40 cm soft slab. In the alpine snow has been redistributed by southerly winds into deep pockets. At treeline and below surface slab overlies a small layer of surface hoar in sheltered and shaded terrain and a sun crust on sunny south-facing slopes.
A weak layer of large surface hoar crystals, facets and a melt freeze crust sits 50-80 cm deep, buried in mid November. This layer has been very reactive at treeline between 1700-2200 m, on all aspects producing large remotely triggered avalanches. This layer will likely continue to be reactive through the week as northerly winds build wind slabs adding additional load to the weak layer.
Snowpack depths average 80-160 cm in the alpine.
Weather Summary
Monday Night
Clear skies with northerly ridge winds 20 km/hr. Alpine temperatures, low of -5. Freezing levels valley bottom.
Tuesday
Sunny with cloudy periods. Northerly ridge wind 25 - 40 km/hr. Alpine temperatures, high of -6. Freezing levels 500m.
Wednesday
A mix of sun and cloud. Northwesterly ridge winds 30 - 50 km/hr. Alpine temperatures, high of -6. Freezing levels valley bottom.
Thursday
Clear skies. Northwesterly ridge winds 40 - 60 km/hr. Alpine temperatures, high of -7. Freezing levels valley bottom.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Give the new snow several days to settle and stabilize before pushing into bigger terrain.
- Don't let the desire for deep powder pull you into high consequence terrain.
- Avoid lee and cross-loaded slopes at and above treeline.
Problems
Persistent Slabs
A weak layer of surface hoar and facets from mid November is buried down 50 to 80cm in the region.
This weak layer continues to catch professionals and recreationists off guard with numerous large, surprise, human-triggered avalanches. Use extra caution at treeline where this layer is more prominent and look for signs of instability like shooting cracks, whumpfing and recent avalanches.
Read our newest blog to learn more about this concerning layer and how to manage it.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Storm Slabs
Warm temperatures and 30 - 40 cm of storm snow have settled into a soft slab. In the alpine southwest winds have drifted snow in some areas and built deep pockets in lees. As winds begin to blow from the north Tuesday watch for reverse loading and cross-loading.
Don't forget that storm slabs could step down to deeper layers resulting in larger and more destructive avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 13th, 2022 4:00PM
