Watch for newly wind-loaded pockets in lee features like ridge crests and steep roll-overs at alpine and treeline elevations.
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. Where wind slabs sit over a crust, they may be more sensitive to triggering.
Wednesday night: Increasing cloud cover. Winds building to moderate southwest. Freezing level 600 m.
Thursday: 5-15 cm new snow. Winds moderate southwest. Freezing level 900 m.
Friday: 5-15 cm new snow. Winds moderate northwest. Freezing level 800 m.
Saturday: 5-15 cm new snow. Winds moderate southwest. Freezing level 1100 m.
Natural wind slab avalanches up to size 2 were observed on steep, north to east facing alpine terrain on Tuesday. A few skier triggered avalanches; wind slab size 1 and a cornice size 2 were reported on Monday and Tuesday. Most were triggered on north to east aspects in the alpine, but one slid on the rain crust on a south aspect at treeline.
A very large (size 3.5) avalanche was observed on Sunday near Whistler on a steep north face at 2400 m. It is suspected to have failed on a layer of facets on a crust from late November. This very large event demonstrates the ongoing need for caution in aggressive alpine terrain.
The new snow is falling on heavily wind-affected surfaces at alpine and treeline elevations. Recent winds have varied in direction so wind slabs can be found on a variety of aspects. A rain crust sits 30-50 cm below the surface at elevations below 2000 m. The bond at this interface appears to be reasonably strong.
While weak faceted grains and crusts near the base of the snowpack have mostly not been a problem recently, one large avalanche was observed on this layer on Saturday Feb 8. The problem appears isolated to very aggressive alpine terrain and is likely more prevalent in inland parts of the region.
