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
