Backcountry avalanche advisory 

As of 2 p.m. Wednesday, Dec. 05

Alpine:  Considerable trending Moderate

Treeline: Moderate trending Low

Below Treeline:  Moderate trending Low

Travel Advisory: A significant change in the weather and snow pack has occurred during the past several days. Strong winds and heavy snowfall on Sunday night gave way to extreme winds and rapidly rising freezing levels on Monday. The light density snow that was out there was covered by a variable layer of deep stiff windslab that has been failing naturally with the rising freezing levels, as well as with explosive and ski testing. They have been propagating far and wide.

Avalanche Activity: Avalanche control conducted during the past few days has resulted in up to size 2.0 avalanche activity within the storm snow layers. Rising freezing levels on Monday saw a widespread natural avalanche cycle begin at all elevations. Several of our alpine slide paths ran full path to size 3.5. While poor visibility has hampered any observations in the backcountry, it is expected that many slide paths have had large slab avalanches run naturally and scour down to the old snow interface. Any slide paths that have already run have been reloading with the continued snowfall.

Snowpack: Heavy wet snow and rain on Monday rapidly increased the load over the assortment of weak layers in the snowpack. Areas exposed to the wind at 2,100 metres and below have a supportive rain crust on the surface. On Tuesday afternoon 30 cm of moist snow was observed to be shearing easily at the underlying interface on lee slopes at this elevation. On Wednesday morning only the top 10-30 cm of new snow was reactive to explosive and ski testing. A gradual cooling trend began last night and will continue over the next 24 hours as the freezing level falls to the valley floor. This will tighten in the snowpack in most areas. However, any areas in the high alpine that did not run during the storm may still have the potential for large slab avalanche activity to occur.

W eather: Periods of flurries today will taper off overnight. Freezing levels currently at 1,200 metres will gradually fall to the valley bottom on Thursday. A ridge of high pressure is expected to develop bringing a mix of sun and cloud on Thursday, with mainly sunny skies and cool temperatures on Friday and Saturday.

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 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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