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Backcountry Avalanche Advisory

As of Tuesday, Dec. 22


Alpine: Considerable through Thursday

Treeline: Moderate through Thursday

Below Treeline: Low through Thursday

Travel Advisory : A total of approximately 75 cm of snow has fallen in the alpine during the storm cycle ending Monday evening. Winds accompanying the snowfall were moderate to strong from the SE and temperatures remained mild. Some natural avalanche activity was observed to have occurred during the storm. Although the windslab was easily triggered yesterday, it is expected to be somewhat less sensitive as a result of overnight cooling. The Nov. 30 th facet/crust weakness is still very much a concern and it is possible that a new snow avalanche could step down to this layer in some slide paths. Travel with caution, as large avalanches could begin to threaten the valley safe routes. The storm snow is very thick and moving through it is a bit of a chore. Give it a few days to settle before heading out into the backcountry.

Avalanche Activity: Explosive and ski testing carried out during the storm cycle produced numerous storm snow avalanches to size 2.5 that were running very easily and propagating widely. Alpine and treeline terrain proved to be particularly reactive. Cornices have grown and they are fragile, pulling back onto the flats in some areas. Earlier in the week we were seeing slabs stepping down to the crust layer resulting with crown lines up to about 120 cm in depth. Heli bombing this morning also produced one deep slab off the Peak in an area that performs very infrequently that is also suspected to have run to the crust/facet layer.

Snowpack: Temperatures have fluctuated during this recent storm giving us variable conditions within the new storm snow, with several softer layers surrounded by denser layers. Moderate to strong winds have made for significant loading in lee alpine terrain, and some ridges are still scoured down to the crust. This week's storm snow is sitting on a mix of crusts and facetted crystals that formed during the cold weather early in December. As previously mentioned, some slabs are failing on this crust layer and a surface slab in motion has the potential to step down to it. This weakness will become increasingly difficult to predict as it gets buried lower within the snowpack, but below 1,600 metres it appears to have been moistened enough to no longer be a factor.

Weather: A building ridge of high pressure is forecast to bring mainly sunny skies and cool temperatures for the duration of the week.

Conditions may vary and can change rapidly. Check for the most current conditions before heading out into the backcountry. Daily updates for the areas adjacent to Whistler Blackcomb are available at 604-938-7676, or surf to where there is also a link to the CAA public avalanche bulletin, or call 1-800-667-1105.

- Whistler Mountain Snow Safety



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