BACKCOUNTRY AVALANCHE ADVISORY 

As of Wednesday, Dec. 27

The Boxing Day storm left us with 37 cm of new snow by the time skies cleared on Dec. 27. Temperatures during the snowfall reached as high as +1.0 C. at 1,835m. Winds were moderate to strong from both the SE and SW. The resulting slab was of the "upsidedown" variety – a relatively stiff windslab overlying a layer of unsettled stellars that fell when the cool temperatures were still prevailing. As one might expect, avalanches were running easily on this layer. During the storm there was widespread natural activity and ski testing produced easy results. On Dec. 27 temperatures cooled. The slab tightened slightly, but was still very reactive to ski testing and explosives. One interesting result on Whistler Mountain was triggered in the storm snow, but pulled down into the November layer of facets. This particular start zone was very rocky and had a shallow snowpack. N and NE aspects seemed to be the most loaded, but we were also seeing some activity on W and NW aspects. A critical variable was whether a slope had the shape that would promote loading from a variety of directions.

You should be aware that a variety of terrain in the backcountry now has the critical load that it hasn’t yet had all season. Rocky terrain at alpine elevations may now begin reacting on the layer of facets. At treeline and below (areas where the surface hoar and facets grew even larger), the storm snow may be the load needed to overstress the weak layers.

Give the snow a chance to settle out. Stay away from rocky, gullied terrain. Watch for wind loaded pockets. The transition from a scoured surface to an ugly windslab can arrive with little warning. Remember that there are still numerous obstacles sticking out of the snowpack. Even a small avalanche can cause very serious traumatic injuries.

The long range forecast is calling for a mix of sun and cloud for the weekend. If you choose to head out into the backcountry, take the cautious lines and be prepared for self rescue.

The backcountry avalanche danger is rated CONSIDERABLE as of Dec. 27. Contact your local ski patrol for the most current information or call 938-7676.

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