North Columbia

Be aware that if triggered, avalanches may step down to deeper layers resulting in large, destructive avalanches. Use extra caution at treeline where weak layers are more prominent and be prepared to back off quickly if you find signs of instability like whumpfing and shooting cracks.

Avalanche reports continued Wednesday. Skiers triggered several size 1-2 slab avalanches in the Selkirks, including a couple of size 1.5 avalanches remotely triggered in treeline openings around 1900-2000 m.

On Tuesday in the northern Monashees, a vehicle remote-triggered a size 2.5 persistent slab avalanche on the mid-November layer. Explosives control produced several size 3 and a size 3.5 persistent slab avalanches.

MIN reports from Monday outside the RMR area boundary document 2 large avalanches triggered by skiers, reported crown depths were 80 cm (Montana1, Montana2).

Several natural storm slab avalanches were reported, up to size 2, every day this week. Several natural persistent slab avalanches, up to size 3, were also reported. These larger avalanches may have been triggered small, solar-triggered avalanches in the afternoon stepping down to deeper instabilities.

Snowpack depths are highly variable and range from 90 cm at treeline to 200 cm in the alpine in wind-affected locations.

Surface: 5-8 mm surface hoar has formed in sheltered areas on the surface of the snowpack. A sun crust is found on steep solar slopes above 2000 m. Northerly winds are creating wind slabs in lees and cross-loading features at higher elevations.

Upper-pack: 40-50 cm settling snow overlies a weak layer of 5 mm surface hoar in sheltered and shaded terrain and a sun crust on sunny south-facing slopes.

Mid-pack: Buried 60-90 cm deep, is a persistent weak layer of surface hoar, crust, and faceted crystals. This layer has been most reactive at treeline between 1700-2200 m, but it was also observed as low as 1450 m and on all aspects.

Lower-pack: Below the mid-November layer is a generally weak, faceted snowpack.

Thursday night

Mostly cloudy and increasing winds. Northwest ridge winds 10-25 km/h. Overnight alpine low temperature -16 C. Freezing levels valley bottom.

Friday

Clear skies with cloud cover increasing later in the day, and possible isolated flurries. Northwesterly ridge winds 10-25 km/h. Alpine high temperature -8 C.

Saturday

Cloudy skies and isolated flurries, trace accumulation. Northwest ridge winds 20 km/h.  Alpine high temperature -10 C.

Sunday

Cloudy skies. Light flurries, up to 5 cm. Northwest ridge winds up to 20 km/h.  Alpine high temperature -16 C.

More details can be found in the Mountain Weather Forecast.

• Be aware of the potential for large, destructive avalanches due to the presence of deeply buried weak layers.
• Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
• Be especially cautious as you transition into wind affected terrain.