Avalanche Forecast

Issued: Feb 12th, 2018 5:31PM

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

Wind slab and cornice hazards remain a real concern. Careful evaluation of terrain, overhead hazards, and wind loading patterns is essential to safe travel.

Summary

Confidence

High -

Weather Forecast

Tuesday: Cloudy with light flurries increasing over the day and bringing 5-10 cm of new snow by Wednesday morning. Mainly light southwest winds becoming strong at higher elevations. Freezing level returning to the surface as the alpine temperature inversion breaks down. Alpine high temperatures around -2.Wednesday: A mix of sun and cloud. Light north winds. Freezing level rising to 700 metres with alpine temperatures of -7.Thursday: Mainly cloudy with light flurries increasing over the day and bringing 10-15 cm of new snow by Friday morning. Light southwest winds increasing overnight. Freezing level to 500 metres with alpine high temperatures of -8.

Avalanche Summary

We have a preliminary report of a snowmobiler that was fatally involved in a cornice failure in the Callaghan area on Saturday. Our understanding is that the individual was parked on or near the cornice when it failed beneath them. This failure resulted in a long fall from ridgetop and the partial burial of the individual in the debris.Reports from Sunday included one observation of a recent natural size 2 cornice release in the Spearhead Range as well as one explosives-triggered size 2 cornice. Warm temperatures and solar exposure caused one natural size 2 loose wet avalanche on a steep alpine slope in the Whistler area.On Saturday, two skier-triggered wind slabs were reported: a size 1.5 wind slab from a cross-loaded feature on a northwest aspect at 1900 m, and a size 2 on a north aspect at 2350 m, both near Whistler.On Friday, evidence of a natural cycle which likely occurred near the end of the warming period earlier in the week was reported, with storm slab activity up to size 3 observed on north to east aspects in the Mt Currie area.

Snowpack Summary

Highly variable snow surfaces exist. On south-facing alpine slopes, you're likely to find scoured crusty surfaces, while reactive wind slabs have built on lee slopes facing roughly north. More recent northerly winds have expanded wind slab formation to a range of other aspects. A melt-freeze crust has formed up to about 1900 m.On average, 180 cm of settled snow now sits on the mid-January crust which generally shows signs of bonding to the overlying snow; however, it has the potential to wake up with a large trigger such as a cornice fall. Below this, the snowpack is thought to be generally strong and well-settled.

Problems

Wind Slabs

An icon showing Wind Slabs
Wind slabs remain reactive to human triggers, especially on leeward slopes and cross-loaded terrain features. Recent shifting winds have been building wind slabs on a wide range of aspects.
Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Use ridges or ribs to avoid steep pockets of wind loaded snow.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Cornices

An icon showing Cornices
Large looming cornices exist along ridgelines. They require respect and discipline. Give them an extra wide berth from above and below. Stiff cornices can easily pull back into flat terrain at ridgetop if they fail.
Falling cornices may trigger large avalanches on the slopes below.Give cornices a wide berth when travelling on or below ridges.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Feb 13th, 2018 2:00PM

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