Avalanche Forecast

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack. Uncertainty is due to the fact that persistent slabs are particularly difficult to 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.