Avalanche Forecast

Issued: Dec 20th, 2016 4:38PM

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

Avalanche Canada jlammers, Avalanche Canada

Continued strong winds will keep the avalanche danger elevated. Be alert to conditions that change with elevation.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Wednesday: Overcast skies / Extreme southwest winds / Freezing level at valley bottomThursday: Mix of sun and cloud / Extreme southwest winds / Freezing level at 1200Friday: Mix of sun and cloud / Extreme southwest winds / Freezing level at valley bottom

Avalanche Summary

Numerous storm slab avalanches (mostly in the size 2 range), were observed failing naturally on Tuesday. The avalanches formed in response to heavy storm loading and failed mostly on north to northeast facing terrain at treeline and in the alpine. Looking forward, continued extreme southwest winds are expected to promote ongoing wind slab activity. There is a bit of uncertainty regarding how the new snow will bond to old surfaces which formed during last week's cold snap. Due to these potentially persistent weak layers, recently formed storm slabs may remain sensitive to human triggering for some time.

Snowpack Summary

Since Sunday up to 60cm of low-density snow has fallen with the highest amounts accumulating in the Lizard Range. Strong winds and slight warming have added cohesion to the new snow and reactive storm slabs exist in wind-exposed terrain. The new snow buries a variable surface that developed over the last week of cold, dry, and windy conditions. This interface consists of scoured surfaces and wind slabs in wind exposed terrain, widespread faceting of the upper snowpack, and surface hoar up to 20 mm in sheltered areas. In sheltered areas, you may find another layer of surface hoar in the mid to upper snowpack which was buried around December 10. The mid pack is generally well settled. The thick crust from mid-November is near the bottom of the snowpack and reports suggest that the crust is currently well bonded to the surrounding snow.

Problems

Storm Slabs

An icon showing Storm Slabs
Wind and warming have added cohesion to the recent storm snow, and storm slabs may be ripe for triggering. Use extra caution in steeper, wind-exposed terrain.
Be cautious as you transition into wind affected terrain.The new snow will require several days to settle and stabilize.Be alert to conditions that change with elevation.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Dec 21st, 2016 2:00PM