Avalanche danger will increase as storm slabs build through the day Sunday. Where new snow depths exceed 30 cm, avalanche danger will rise to HIGH at alpine and treeline elevations.
Heavy snowfall through the day Sunday will bring totals of 30-50 cm since Friday night. The new snow is not expected to be bonding well to old surfaces including surface facets, surface hoar and sun crusts. Storm slabs will be deepest in lee terrain features near ridges, as the snow is falling with strong southwest wind.
Saturday night: Light flurries bringing up to 5 cm new snow. Light to moderate southwest wind. Alpine low -7 C. Freezing level 900 m.
Sunday: 20 to 40 cm new snow with lighter accumulations around Whistler. Strong southwest wind. Alpine high -6 C. Freezing level 1000 m.
Monday: Mix of sun and cloud. Light to moderate northwest wind. Alpine high -4 C. Freezing level 700 m.
Tuesday: Mostly cloudy with isolated flurries. Light to moderate southwest wind. Alpine high -3 C. Freezing level 900 m.
The only reports of avalanche activity on Thursday or Friday were a few isolated skier triggered wind slabs to size 1 and cornice control work to size 2.
A widespread natural storm slab avalanche cycle is expected Sunday with significant new snow and wind.
20-40 cm of new snow is forecast to fall through the day Sunday. Forecast strong southwest winds are expected to redistribute the new snow at alpine and treeline elevations, loading deep deposits into lee features. These storm slabs may slide easily where they overly a layer of widespread surface facets, surface hoar in sheltered areas or sun crusts on solar aspects.
Faceted snow and crusts exist near the base of the snowpack in much of the region. This layer is dormant at the moment but appears to be most likely a problem on the eastern side of the region, in alpine terrain, and where there is relatively smooth ground (e.g., glaciers, scree slopes, rock slabs).
