Backcountry Advisory 

As of Wednesday, Dec. 5

Things have settled down nicely since the weekend, allowing us to catch our breath and enjoy some mighty fine powder conditions. Last weekend’s storm cycle dominates the big picture for the past week’s events as we received up to 80 cm of new snow, with some ferociously strong winds and nice cold temperatures. This dramatically transformed the mountains into a much more seasonal top-to-bottom play ground. Since Sunday, temperatures have remained cold, with a further 10 cm of nice light new snow. All in all a hell of a good start to the season.

Generally our local snowpack is looking quite strong and consolidated for this early in the season but a few features are worth noting. New snow instabilities developed rapidly through the storm period, although much of the alpine was generally inaccessible due to high winds. On Sunday numerous soft slab avalanches occurred with explosive control and ski triggers. The slabs ranged from 20 cm to close to a metre in thickness and mostly appeared to be shearing within the storm snow layers. These new snow weaknesses have been steadily gaining strength as the new snow layers settle and sinter, but they may still be ski triggerable in some extreme terrain.

A few slabs were noted shearing deeper on the November rain crust mentioned in last week’s advisory. This crust had been weakened due to a strong temperature gradient prior to the storm cycle. The resultant faceted crystals above and below the crust are most evident in areas which were shallow snow pack areas prior to the storm, such as steep rocky start zones which have not fattened up yet, or typically wind-affected areas such as west and south aspects. More recently a layer of surface hoar formed everywhere but above tree line and now lies under 10 cm of new snow. Both the surface hoar and faceted crust weaknesses are known as persistent weaknesses and thus should be watched for carefully as we receive further loading.

The forecast calls for a series of frontal systems to nail us once again. The first, on Thursday, should stay cool and may give us only 5 to 10 cm of snow. The next arrives Friday with perhaps more precipitation but also the likelihood of freezing levels rising half way up the mountains. Currently the Avalanche Hazard is rated as MODERATE and will likely increase to CONSIDERABLE toward the weekend.

For daily avalanche assessments call 604-938-7676 for areas adjacent to Whistler and Blackcomb mountain. If travelling further call 604-290-9333 or www.avalanche.ca for bulletins covering most of Western Canada

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