New snow and wind will sustain wind slab development. Expect to find a more reactive snowpack in areas with heavier snowfall rates. And in areas where more than 20 cm fresh snow accumulates, avalanche hazard will be Considerable.
New snow and wind will further wind slab development in lee features at alpine and treeline elevations. Recent winds have varied in direction so wind slabs can be found on a variety of aspects. Be mindful that wind slab avalanches can serve as triggers for deeper weak layers, resulting in large and destructive avalanches.
FRIDAY NIGHT: Cloudy with scattered flurries, 5-10 cm. Alpine low temperature -9 C. Southwest wind 15 gusting to 45 km/hr. Freezing level 600 m.
SATURDAY: Cloudy with isolated flurries, 5-15 cm with up to 20 cm accumulation around the Coquihalla and south to Allison Pass. Alpine high temperature -5 C. Southwest wind 15 gusting to 45 km/hr. Freezing level rising to 1100 m.
SUNDAY: Mix of sun and cloud with isolated flurries, up to 5 cm. Alpine high temperature -9 C. West wind 15 gusting to 40 km/hr. Freezing level 800 m.
MONDAY: Mix of sun and cloud. Alpine high temperature -9 C. Northwest wind 15-25 km/hr. Freezing level 900 m.
Natural wind slab avalanches up to size 2 were observed on steep, north to east facing alpine terrain on Tuesday.
On Wednesday, two cases of wind slab avalanches stepping down to deep persistent layers were reported: one was skier triggered from a thin spot in an aggressive north facing alpine feature (link to MIN report), the other a natural size 2.5 on a convex southeast aspect in an open area around treeline. In the neighbouring Sea to Sky region, a very large (size 3.5) avalanche occurred on Sunday near Whistler on a steep north face at 2400 m. These avalanches are suspected to have failed on a layer of facets on a crust from late November. These events demonstrate the ongoing need for caution in aggressive terrain, particularly in areas where deep instabilities remain.
New snow and wind will further wind slab development in lee features at alpine and upper treeline elevations. Prior to the overnight flurries, recent winds redistributed recent snow producing windslab in the alpine and upper treeline, up to 20 cm less dense snow in more sheltered terrain, and a thin suncrust on solar aspects. This older snow overlies a couple of crusts deeper in the snowpack, down 30-40 cm and 60-110, over a settled mid-pack.
In the north part of the region (ie. Goldbridge/Duffey/Hurley), a few deep instabilities exist in the snowpack, including a weak basal facet crust complex. Sporadic avalanche activity on these layers keep them on our radar. In the south of the region, including the Coquihalla and Manning areas, we currently have no concerns about deeply buried weak layers.
