Avalanche Forecast

Issued: Dec 1st, 2018 4:29PM

The alpine rating is moderate, the treeline rating is low, and the below treeline rating is low. Known problems include Wind Slabs and Cornices.

Avalanche Canada cgarritty, Avalanche Canada

Conditions vary dramatically by elevation. Expect to find lingering cornice and wind slab problems as you reach the alpine.

Summary

Confidence

High -

Weather Forecast

Saturday night: Clear periods with decreasing cloud. Light northeast winds.Sunday: A mix of sun and cloud. Light northeast winds. Alpine high temperatures around -7.Monday: Mainly sunny. Light northeast winds. Alpine high temperatures around -6.Tuesday: Sunny. Light north winds. Alpine high temperatures rising to -2 as a temperature inversion establishes.

Avalanche Summary

Explosives control work in the Whistler area on Friday produced several size 1.5 cornice releases and one 20 cm deep size 1.5 storm slab. On Wednesday cornices were touchy; a size 1.5 cornice failure was initiated with a very light load. Control work produced storm slabs that averaged size 1.5 on a variety of aspects in the alpine. The outlier was a size 3 avalanche induced by control work on a south facing alpine feature which stepped down to the early November crust.Skies cleared Tuesday allowing some observation of avalanches that likely released at the height of the storm. A large (size 2.5) avalanche was reported on a northeast facing glacial feature between 2100 and 2200 m. The avalanche failed naturally with a crown up to 1 meter in depth. Another large natural avalanche (size 2) was reported from a north facing feature near 2000 m. Please submit any observations you have to the Mountain Information Network here,

Snowpack Summary

The storm from early last week brought intense precipitation that rain-soaked the existing snowpack up to about 1800 m and left 20 to 30 cm of wet snow in place up to 2000 m. Above 2000 m the storm produced around 60 cm of new snow. The upper 20 to 30 cm of snow is reportedly dry in the alpine. Strong to extreme wind during the storm formed storm slabs and cornices in high elevation alpine terrain. Above 2000 m, 50 to 200 cm of snow now sits on the early November melt-freeze crust. Little is known about the reactivity of this interface in the alpine. This crust may be associated with weak faceted crystals in some places where it lies close to the ground. This is most likely to cause problems in glaciated terrain or on smoother, high elevation slopes where the summer snow did not melt out.

Problems

Wind Slabs

An icon showing Wind Slabs
Soft slabs up to 30 cm in depth exist in the alpine. Cooling temperatures continue to reduce the slabs sensitivity to human triggering, however slabs in extreme terrain and immediately lee of ridgecrest will take the longest to stabilize.
If triggered, wind slabs may step down to deeper layers resulting in large avalanches.Be cautious around mid-slope terrain features like ridges and ribs where slabs may be deeper.Use caution in alpine lees. Recent snowfall mixed with wind loading has created slabs.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Cornices

An icon showing Cornices
Touchy cornices have formed on many alpine ridgelines. These cornices may be large and weak. Do not trust them and avoid travel on or underneath them.
Stay well back from cornices when traveling on ridgelines.Do not travel on slopes that are exposed to cornices overhead.Extra caution needed around cornices with current conditions.

Aspects: North, North East, East, West, North West.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 2nd, 2018 2:00PM