Avalanche Forecast

Issued: Dec 10th, 2016 4:07PM

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

Avalanche Canada jsmith, Avalanche Canada

Recently formed wind slabs may remain reactive to human triggers for several days. Continue to investigate the layer of surface hoar down 60-120 cm.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Sunday: Mostly sunny / Light to moderate easterly winds / High of -19 C.Monday: Sunny / Light northeasterly winds / High of -15 C.Tuesday: Sunny / Light northeasterly winds / High of -15 C.

Avalanche Summary

Wind slab avalanches are a concern in all areas within the region, and could easily step down to the surface hoar layer below. This surface hoar layer may remain reactive to human triggers for a longer period than is common for this region because it is being well preserved my cold temperatures.

Snowpack Summary

Clear skies and strong outflow winds have created a variety of snow surfaces including scouring and hard wind slabs in exposed areas and up to 12 mm surface hoar formation in sheltered areas. Strong to extreme easterly winds over the past few days have created wind slabs on aspects you may not expect them. Wind slabs could be present on all aspects in exposed alpine, treeline, and even some below treeline locations. A layer of surface hoar which was buried around November 22nd is down 60-120 cm in many parts of the region. This layer is likely still reactive to human triggers. A thick rain crust exists 20-30 cm below the surface hoar layer, with isolated reports of weak facets (sugary snow) forming above the crust; however, that interface has not become a concern as of yet. 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

Wind Slabs

An icon showing Wind Slabs
Recently formed wind slabs may remain reactive to human triggers for several days after the winds die down. Wind slabs may be present on many aspects and elevations due to very strong and highly variable wind directions.
Use ridges or ribs to avoid pockets of wind loaded snow.Avoid areas where the snow feels stiff or 'slabby'.Be aware of the potential for wide propagations due to the presence of hard windslabs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
A persistent weak layer of touchy surface hoar is buried 60-120 cm deep throughout the region, and may be reactive to human triggers. Smaller wind slabs may step-down to this layer resulting in large avalanches.
Avoid slopes where buried surface hoar is preserved. Remote triggering from a distance is possible.Dig down to find and test weak layers before committing to a line.Be aware of the potential for large avalanches due to the presence of buried surface hoar.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3

Valid until: Dec 11th, 2016 2:00PM

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