It's not a trustworthy snowpack. Fresh surface instabilities and deeply buried weak layers have combined to create dangerous avalanche conditions.
Round after round of moderate to heavy snowfall and strong to extreme wind has formed new and recent wind slabs of varying reactivity. Large wind slab releases may step down to deeper weak layers to create very destructive avalanches.
Buried weak layers are most concerning at treeline elevations. Small avalanches may step down to this layer resulting in very large destructive avalanches. These avalanches may also be triggered remotely.
Bouts of sunshine on steep sun-exposed slopes could quickly initiate wet loose avalanche activity on Wednesday.
Mondays reports included several size 2 to 2.5 wind slabs controlled with explosives in the Whistler area. These were 60 - 90 cm deep and propagated widely. More sheltered terrain produced 20 cm storm slabs with ski cutting.
Numerous size 2 slab avalanches were triggered by riders in the Whistler area on Sunday with crown depths of 40 to 80 cm. Explosive control also produced a few very large (size 3 to 4) avalanches that failed on the early February persistent weak layer.
20-40 cm of new snow in the early week overlies previous wind slabs, low density snow in sheltered areas, and, in the Whistler area, a thin crust at treeline. It also brought 4-day storm totals in the region to 80 - 160 cm. Strong to extreme winds have continued to redistribute loose surface snow into thick slabs.
A weak layer composed of facets on a crust is buried beneath the recent snow, in wind-loaded areas now 150 to 250 cm deep. This layer remains sensitive to both human and natural triggers and is capable of producing very large, very destructive avalanches.
The snowpack below this interface is generally well settled and strong.
Tuesday night
Cloudy with isolated flurries and a trace of new snow. 10 - 15 km/h west ridgetop wind. Freezing level remaining near 1000 m.
Wednesday
Mainly cloudy. 10 - 15 km/hr west or northwest ridgetop wind. Treeline temperature -4 °C with freezing level rising to 1300 m.
Thursday
Mainly sunny. 20 - 30 km/hr northwest ridgetop wind. Treeline temperature +5 °C with freezing level shooting to 3300 m.
Friday
Sunny. 15 - 25 km/h northwest ridgetop wind. Treeline temperature +10 °C with freezing level to 3500 m.
More details can be found in the Mountain Weather Forecast.
