Backcountry Advisory 

Take caution on lee slopes

Forecast of Avalanche Danger as of Tuesday Dec. 27, 2005

Alpine: CONSIDERABLE

Treeline: MODERATE

Below Treeline: Below threshold

Travel Advisory : We have received 24 cm of new snow in the alpine during the past 24 hours, accompanied by moderate and at times strong winds from the South and Southeasterly directions. Caution is advised on any lee slopes as a surface slab in motion has the potential to step down deeper within the storm snow layers. On Saturday rain fell up to the mountaintops. You will still find some moist layers below the storm snow in the alpine and at treeline elevations. Below treeline a thin covering of storm snow overlies the moist, isothermal old snow layers. These layers will not support the weight of a person and will make traveling very difficult. Restrict your travel to the upper elevation terrain or you may find yourself wallowing through knee-deep slop.

Avalanche Activity : A large natural avalanche cycle was observed to have occurred in the backcountry when rain fell up to the mountaintops last Saturday. Strong winds over the past 48 hours have resulted in large stiff cornice development, many of which have failed easily during the past few days. Although the light density snow that fell overnight resulted in soft slab formation with only limited propagation, a stiff windslab was observed yesterday on North aspects. This windslab was very reactive to both explosive and ski testing, propagating easily over long distances. In some areas this surface slab in motion stepped down to the moist underlying layers.

Snowpack : The old faceted layers have been moistened by the rain and will hopefully stabilize as cooler temperatures slowly permeate through the snowpack. On North aspects in the high alpine up to 70 cm of storm snow is on top of the underlying rain-moistened snowpack. As you get closer to treeline the snowpack has become isothermal and lost all of its strength. It will take a while for the colder temperatures to permeate down and solidify the rain-soaked layers of snow.

Weather: The extended outlook is calling for a series of systems from the West to bring us periods of snowfall throughout the week and into the weekend, with freezing levels fluctuating between 1,000 metres and 1,500 metres.

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 at www.whistler-blackcomb.com/weather where there is also a link to the CAA public avalanche bulletin, or call 1-800-667-1105.

— Whistler Mtn. Snow Safety

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