Kootenay Boundary

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.

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 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.

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.

• 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.