Avalanche Forecast

Issued: Dec 13th, 2016 4:03PM

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

jsmith, Avalanche Canada

Northwest Coastal.

A weak layer of surface hoar that is now buried around a metre deep is creating a low likelihood, high consequence scenario. Continue to investigate this layer carefully.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Wednesday: Sunny / Light northeasterly winds / Average temperature at treeline -8 C.Thursday: Sunny / Moderate northeasterly winds / Average temperature at treeline -15 C. Friday: Mix of sun and cloud / Light northwesterly winds / Average temperature at treeline -13 C.

Avalanche Summary

No recent avalanches have been reported in this region.

Snowpack Summary

Clear skies and strong outflow winds have created a variety of snow surfaces including scouring and hard slabs in exposed areas and up to 12 mm surface hoar formation in sheltered areas. Strong easterly winds over the past week have created wind slabs on aspects you may not expect them. Wind slabs could be present on all aspects in open areas at treeline and above. A layer of surface hoar which was buried mid-November is down 60-120 cm in many parts of the region. This layer may be reactive to human triggers in isolated locations or could be triggered by a smaller slab that 'steps-down' to this layer. Treeline snow depths are around 140-200 cm in the Terrace and Stewart areas, but substantially less further north. Concerns in the north are basal weaknesses that may exist in the shallower snowpack areas especially on smooth alpine features like glaciers.

Problems

Persistent Slabs

A persistent weak layer of surface hoar is buried 60-120 cm deep throughout the region, and may be reactive to human triggers in isolated locations. Smaller wind slabs may step-down to this layer resulting in large avalanches.

Be aware of the potential for large avalanches due to the presence of buried surface hoar.Dig down to find and test weak layers before committing to a line.Avoid slopes where buried surface hoar is preserved.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Wind Slabs

Lingering wind slabs may be present on many aspects and elevations due to strong and highly variable wind directions.

Be aware of the potential for wide propagations due to the presence of hard windslabs.Avoid areas where the snow feels stiff or 'slabby'.Use ridges or ribs to avoid pockets of wind loaded snow.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 14th, 2016 2:00PM