Avalanche Forecast

Issued: Dec 22nd, 2016 5:03PM

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

jfloyer, Avalanche Canada

Northwest Inland.

Attention sledders: Be particularly careful pushing into new areas that have not been heavily ridden. Lower layers are triggerable, particulary on convex features and where hard wind slabs have formed.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Friday: Dry and sunny. Winds mostly light northeasterly. Alpine temperatures around -16C. Saturday: Dry and sunny. Winds mostly light from the northeast. Alpine temperatures around -17C. Sunday: Increasing cloud. Winds increasing through the day to 40km/h southwesterly by the afternoon. Temperatures around -17C.

Avalanche Summary

A widespread natural storm cycle up to size 3 was reported that ended on Wednesday. Human triggering remains likely, especially in terrain that has not been heavily ridden.

Snowpack Summary

Up to 50 cm new storm snow now sits over a highly variable interface comprising of wind-scoured surfaces, hard wind slabs, faceted (sugary) snow, and maybe some feathery surface hoar in sheltered areas. The new appears to have bonded poorly to this interface. The winds were extreme through much of the storm, and hard wind slabs now exist behind exposed terrain features. The snowpack is still shallow throughout the region and widespread faceting of the entire snowpack is likely in most areas. A thick rain crust that formed in early November is probably near the bottom of the snowpack and is probably surrounded by sugary facets. Basal facets and depth hoar (more sugary crystals) right at the bottom of the snowpack are reportedly widespread.

Problems

Wind Slabs

Up to 50 cm recent storm snow has fallen, accompanied by strong winds. Storm slabs are likely on steep terrain, particularly unsupported terrain; wind slabs are likely in exposed lee areas.

Be aware of the potential for wide propagations due to the presence of hard windslabs.The new snow buries a weak layer which may increase the reactivity of new slabs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

A substantial amount of new snow has loaded two layers of weak, faceted snow: one is buried around 50 cm and one near the base of the snowpack. Likely trigger points are unsupported (convex) slopes in shallower snowpack areas.

Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.Avoid unsupported slopes.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Dec 23rd, 2016 2:00PM