Avalanche Forecast
Issued: Dec 13th, 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
We continue to receive reports of large natural and human-triggered avalanches on the persistent weak layer. Keep your terrain choices conservative and be prepared to back off quickly if you find signs of instability; whumpfing and shooting cracks.
Read our featured blog to learn more about how to manage a persistent slab problem when traveling in the backcountry.
Summary
Confidence
Moderate
Avalanche Summary
On Monday, several, size 2.5 natural persistent slab avalanches were observed in the Kaslo region. Explosives control throughout the Selkirks triggered size 2.5 avalanches on the mid-Niovember weak layer.
On Sunday, numerous surprise human-triggered avalanches were reported on the persistent weak layer 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.
Backcountry users throughout the region continue to report signs of instability: whumpfing and shooting cracks.
Snowpack Summary
5 - 10mm surface hoar is forming on a 30 - 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
Tuesday Night
Mainly cloudy. Isolated flurries for the Purcells, trace accumulation. Northerly ridge wind 20 - 30 km/hr. Alpine temperatures, low of -10. Freezing levels valley bottom.
Wednesday
Sunny with cloudy periods. Isolated flurries for the Purcells, 2-5 cm accumulation. Northerly ridge wind 20 - 40 km/hr. Alpine temperatures, high of -6. Freezing levels valley bottom.
Thursday
Partly cloudy skies. Northwesterly ridge winds 20 - 30 km/hr. Alpine temperatures, high of -7. Freezing levels valley bottom.
Friday
Partly cloudy skies. Northwesterly ridge winds 40 - 60 km/hr. Alpine temperatures, high of -8. Freezing levels valley bottom.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
- Don't let the desire for deep powder pull you into high consequence terrain.
- Give the new snow several days to settle and stabilize before pushing into bigger 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 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.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Storm Slabs
30 - 40 cm of storm snow has settled into a cohesive 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 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 14th, 2022 4:00PM
