Backcountry Avalanche Advisory 

As of Wednesday, Jan. 7

Alpine: Extreme, trending High with cooling

Treeline: Extreme, trending High with cooling

Below Treeline: High, trending Moderate with cooling

Travel Advisory: The current avalanche conditions are unusual for the coast. The skiable lines that have finally filled in are often where the avalanche hazard is at its worst. Ongoing snowfall combined with strong winds and recent rising freezing levels has loaded a variable series of hard and soft slabs over the weak lower snow pack. The underlying weaknesses are becoming very reactive and sometimes failing with light loads. Avalanches are being remotely triggered from a distance and some lower angle areas are settling or "whumphing" repeatedly. In some cases these slopes are reacting after being tested with explosives. Travel in avalanche terrain should be avoided and travel confined to low angle terrain well away from avalanche path runouts.

Avalanche Activity: Explosive testing and ski cutting carried out during the past week has produced numerous slab avalanches up to two metres in depth. They have been failing in the storm snow and in the facets above the Dec. 6th crust. Some slopes at treeline elevations have run on a layer of depth hoar in the rocks and on the heather. Many settlement whumphs have also been heard. Rising freezing levels and heavy snowfall overnight resulted in natural avalanche activity up to one metre in depth on some treeline slopes, with numerous slopes running within the storm snow. At lower elevations rainfall produced widespread loose sluffing and snowballing, with some steep creek beds and drainages producing nasty debris piles in the deposition zones.

Snowpack: We are currently experiencing a snowpack that is not typical for the West Coast. The previously shallow snowpack that was exposed to prolonged cold temperatures became weak and faceted, with depth hoar forming in shallow rocky terrain. Compounding this problem is the underlying Dec. 6 raincrust. Shallow areas have thin surface weaknesses over depth hoar crystals. The buried facets and depth hoar above and below the Dec. 6 crust are weak layers and very likely the cause of the settlement whumphs. The crust/facet combo is now buried up to 200 cm below the surface on some lee slopes. Not all start zones are running on the crust, but you can expect more widespread activity as the load above it grows. Rocky terrain is very rotten and will be particularly prone to deeper releases in the future. Below treeline terrain has a weak layer on the ground. This terrain has recently been getting filled in and has been producing avalanche activity this week, with increased activity observed with the recent rainfall.

Weather: The heavy snowfall in the alpine and rainfall at lower elevations today will taper off overnight tonight and tomorrow with freezing levels falling to around 1,200 m tonight. Sunny breaks on Friday will give way to another system on Friday night or 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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