Reverse wind-loading and a buried weak layer warrant careful terrain choices. Seek out softer conditions wind-sheltered areas.
Recent winds have shifted from south to north with an ample supply of light, cold snow to drift into reactive slabs. Watch for unusual cross-loading or reverse-loading patterns in wind-exposed areas, and anticipate reactive wind slabs on a variety of aspects.
A layer of weak facets (sugary snow) can be found down 70 - 150 cm near a crust that formed in early December. Cornice falls or wind slabs in motion may step down to this layer and trigger large destructive avalanches. It is more likely to human trigger this persistent slab in thin areas at tree line elevations.
Cold arctic air sits over the region with little change in weather conditions over the next few days.
MONDAY NIGHT: Mostly clear skies, no significant precipitation, moderate wind from the northwest, treeline temperatures around -22 C.
TUESDAY: Sunny with a few clouds, no precipitation, moderate wind from the northwest, treeline temperatures around -20 C.
WEDNESDAY: Sunny with a few clouds, no precipitation, moderate wind from the north with gusts to 60 km/h, treeline temperatures around -20 C.
THURSDAY: Cloudy, light flurries with 5 cm of low density snow, light to moderate wind from the northwest, treeline temperatures around -16 C.
There have been regular reports of small to large (size 1-2) wind slab avalanches in the Duffey Lakes area over the past few days. These included some natural avalanches on south aspects, that were the direct result of reverse loading. Based on this pattern we can expect to find reactive wind slabs in unusual locations over the upcoming days.
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 in the neighbouring Sea-to-Sky region.
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 in the Sea-to-Sky region. 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.
20-30 cm of low density snow can be found in many locations, although gusty conditions have been causing highly variable wind loading patterns. The current weather could quickly form reactive slabs on leeward slopes, including unusual cross-loading or reverse-loading patterns in wind-exposed areas. 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 layer of facets (sugary snow) can be found over a widespread crust that formed in early December (down 70-150 cm). This layer has been particularly reactive at treeline and low alpine elevations, between 1500-2100 m. Large (size 2-3) avalanches have been reported recently in the neighbouring Sea-to-Sky region. This problem is particularly hard to predict and tricky to manage. Get more details and photos in our forecaster blog.
