Avalanche Forecast

Cold, Arctic air and north winds take the reins

Sunday night: Mostly clear, no new snow expected, light northeast winds increasing to moderate in the alpine, treeline low temperatures near -25 C.

Monday: Mix of sun and cloud, no new snow expected, winds becoming northwest and increasing to moderate, treeline high temperatures near -18 C.

Tuesday: Mostly clear, no new snow expected, moderate northwest winds increasing to strong in the alpine, treeline high temperatures near -12 C. 

Wednesday: Increasing cloudiness, no new snow expected, moderate northwest winds increasing to strong in the alpine, treeline high temperatures near -14 C.

Wind slab avalanches will likely be sensitive to triggering on Monday, especially near ridge crests and roll-overs. Over the past few days, operators have reported numerous small to large (up to size 2.5) explosive-triggered avalanches releasing in the storm snow on a variety of aspects. 

Cornices are large and looming and have the potential to trigger large avalanches on slopes below. Several large (up to size 2) cornices have been both human-triggered and explosive-triggered this week.

It remains possible to human-trigger large persistent slab avalanches, particularly in shallow snowpack areas at treeline and low alpine elevations. On Friday, a large (size 2.5) persistent slab avalanche was skier-triggered in the backcountry near Blackcomb. It released 110 cm deep on the early December crust layer on a northwest facing slope around 2100 m in a shallow rocky start zone. 

Since Friday, 20-35 cm of low density snow has fallen a variety of surfaces, including well-settled snow, wind-packed or wind-scoured surfaces, and a possible surface hoar or rime crust layer. 

Northerly outflow winds have an ample supply of light, cold snow to drift into reactive slabs on leeward slopes. Watch for unusual cross-loading or reverse-loading patterns in wind-exposed areas, and anticipate reactive wind slabs on a variety of aspects. Sensitivity to triggering will be greatest near ridge crests and roll-overs. Monitor for changing slab conditions as you move into wind-exposed terrain, and give cornices a wide berth.

A concerning weak layer of facets (sugary snow) can be found over a widespread crust that formed in early December (down 100-200 cm). This layer has been most reactive at treeline and low alpine elevations, between 1500-2100 m. Large (size 2-3) avalanches have been reported recently on this layer. This problem is particularly hard to predict and tricky to manage. Get more details and photos in our forecaster blog. 

• Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
• Recent wind has varied in direction so watch for wind slabs on all aspects.
• If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
• Be especially cautious near rock outcroppings, on steep convexities and anywhere the snowpack feels thinner than average.
• Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.