Avalanche Forecast

Issued: Dec 21st, 2016 4:22PM

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

jfloyer, Avalanche Canada

Northwest Inland.

In the come-down after the storm, watch for wind slabs in all exposed terrain and the potential for triggering deeper layers on unsupported (convex) terrain features.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

Thursday: Cloudy but mostly dry. Winds diminishing to around 30 km/h from the northwest. Alpine temperatures around -7C.Friday: Dry with some sunny breaks. Winds light southeasterly. Alpine temperatures around -12C.Saturday: Dry and sunny. Winds light northeasterly. Alpine temperatures around -20C.

Avalanche Summary

Storm slab avalanches were reported from the region on Wednesday with few details, and we previously had reports of two small avalanches on north facing terrain on Sunday.

Snowpack Summary

Up to 60 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 snow is expected to bond poorly to this interface, but observations to confirm this are hard to come by. The winds have been cranking, and the new snow has been blowing into wind slabs 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. Reports from the Ningunsaw Pass area and the far north of the region suggest that depth hoar is developing in shallow snowpack areas.

Problems

Storm 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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Valid until: Dec 22nd, 2016 2:00PM