Avalanche Forecast

Issued: Feb 13th, 2018 5:14PM

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

Avalanche Canada cgarritty, Avalanche Canada

Stay disciplined while avalanche danger is heightened. Wind slabs remain reactive to human triggering and will be building with new snow and wind over Tuesday night

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

Tuesday: Flurries bringing around 4-8 cm of new snow. Moderate to strong west winds.Wednesday: Mainly cloudy with isolated flurries and a trace of new snow. Moderate north winds. Alpine high temperatures of -9 in the north of the region, closer to -3 in the south.Thursday: A mix of sun and cloud with cloud and light flurries building over the day. Light southwest winds. Alpine high temperatures of -12 in the north of the region, closer to -6 in the southFriday: A mix of sun and cloud with isolated flurries and a trace of new snow. Moderate northwest winds. Alpine high temperatures of -10 in the north of the region, closer to -3 in the south.

Avalanche Summary

Reports from Sunday included observations of numerous small wind slabs releasing with skier traffic and ski cutting on steep treeline and alpine features in the north of the region. This was after a bout of intense wind loading from strong to extreme northerly winds. One natural size 2.5 wind slab release was also observed on a southeast aspect.On Saturday, skiers triggered a size 2 wind slab on a north east aspect near 2000m in the Duffey zone. See the MIN report for more details. Friday there were isolated reports of natural cornice triggered and wind slab activity up to size 2.5, as well as evidence of an older large, natural size 3.5, in high alpine terrain in the Duffey Lake area.On Thursday, the southern part of the region reported a natural slab avalanche size 3.5 from a NE-SE aspect near 1800 m and numerous wet slabs up to size 2.5. An avalanche control mission using explosives in the northern part of the region saw wind slab results up to size 1.5, only running in the surface snow and not stepping down deeper.

Snowpack Summary

5-10 cm of new snow is expected to fall by Wednesday morning. The new snow is accumulating above unconsolidated recent storm snow in wind-sheltered, shaded areas at upper elevations as well as variably scoured and wind loaded slopes in exposed areas. The recent storm snow amounts to roughly 60 cm in the south of the region and about half this amount in the north of the region. Below about 1800 metres, the new snow will accumulate above a rain crust.About 80-150 cm down in the mid snowpack sits the mid-January crust. It generally shows signs of bonding to the overlying snow but will likely remain sensitive to large triggers - especially in thinner snowpack areas. Large, looming cornices exist, they are fragile, and they demand respect. Cornice falls are very effective triggers for avalanches on the slopes below them.

Problems

Wind Slabs

An icon showing Wind Slabs
Reactive wind slabs exist, especially around ridge crests where more wind loading has occurred. Recent shifting wind patterns have formed slabs on a wide range of aspects. New snow and wind will add to this problem on Tuesday night.
Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Don't let human factors push you into the wrong terrain while avalanche danger is elevated.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Cornices

An icon showing Cornices
Large, looming cornices have formed along ridgelines. They need to be given an extra wide berth from above and below. A large cornice collapse in the north of the region may have the ability to trigger a deeply buried weak layer.
Firm cornices can pull back into flat terrain at ridgetop if they fail.Falling cornices may trigger large avalanches on slopes below.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1.5 - 3.5

Valid until: Feb 14th, 2018 2:00PM