Avalanche Forecast
Issued: Dec 15th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs.
dsaly,
Avalanche Canada
Be aware that if triggered, avalanches may step down to deeper layers resulting in large, destructive avalanches. Keep your terrain choices conservative and be prepared to back off quickly if you find signs of instability like whumpfing and shooting cracks.
Summary
Confidence
Avalanche Summary
On Wednesday, a few skier-triggered avalanches to size 1 were reported along with ongoing whumpfs and reactive snowpack test results.
On Tuesday, explosives control in the Monashees produced a few avalanches below treeline up to size 2.
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-November weak layer.
On Sunday, numerous surprise human-triggered avalanches were reported on the persistent weak layer between 2200 and 1700 m. The spookiest reports were a very large size 3 avalanche remotely triggered by skiers near Kokanee Glacier, and a size 2.5 avalanche failing sympathetically with a smaller avalanche near Kaslo. These avalanches either failed on the November weak layers or started as smaller avalanches and stepped down to these deeper instabilities.
Snowpack Summary
Snowpack depths average 80-160 cm in the alpine.
Surface: 5-10 mm surface hoar has formed on the surface of the snowpack. A sun crust is found on steep solar slopes. Previous southerly winds have created wind slabs in exposed lees and cross-loaded features at higher elevations.
Upper-pack: A 30-40 cm soft slab overlies a small layer of surface hoar in sheltered and shaded terrain and a sun crust on sunny south-facing slopes.
Mid-pack: 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.
Lower-pack: Below the mid-November layer is a generally weak, faceted snowpack.
Weather Summary
Thursday night
Scattered clouds. Northwest ridgetop winds 15-25 km/hr. Overnight alpine low temperature -14 C. Freezing level valley bottom.
Friday
Partly cloudy skies. Northwesterly ridge winds 10-20 km/h. Alpine high temperature -8 C.
Saturday
Cloudy skies and isolated flurries, trace accumulation. Southwest ridge winds 15-25 km/h. Alpine high temperature -10 C.
Sunday
Cloudy and isolated flurries, up to 5 cm. Light south ridgetop wind. Alpine high temperature -14 C.
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.
- Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
Problems
Persistent Slabs
There are now two persistent weak layers within the snowpack.
A 30 - 40 cm soft slab sits above a weak layer of surface hoar on shaded aspects and crust on steep solar aspects. Although natural avalanche activity has tapered off on this layer, human-triggered avalanches are possible.
A second weak layer of surface hoar and facets from mid-November is buried down 50 to 80cm in the region. This layer continues to catch professionals and recreationists off guard with numerous large human-triggered avalanches.
Read our featured blog to learn more about how to manage a persistent slab problem when traveling in the backcountry.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 16th, 2022 4:00PM
