Avalanche Forecast

Issued: Feb 13th, 2018 5:11PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate. 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 forecast new snow is not expected to bond well to the weak surfaces that developed during the clear period.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

Tuesday night: Flurries bringing around 6-12 cm of new snow. Light to moderate southwest winds. Wednesday: Mainly sunny. Light to moderate northeast winds. Freezing level to 1000 metres with alpine high temperatures around -7.Thursday: A mix of sun and cloud with increasing cloud and light flurries over the day. Light southwest winds. Freezing levels down to 500 metres with alpine high temperatures of - 11.Friday: A mix of sun and cloud. Light northwest winds. Freezing level to 800 metres with alpine high temperatures around -7.

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. Please see this MIN report for details.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

Increasing flurries are expected to bring about 15 cm of new snow to the region by Wednesday morning. Beneath the new snow, highly variable snow surfaces exist. From scoured crusty surfaces on south-facing alpine slopes to reactive wind slabs on lee slopes facing roughly north. More recent northerly winds have expanded wind slab formation to a range of other aspects and melt-freeze crust exists 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
Light new snow and moderate winds over Tuesday night will contribute to an active wind slab problem. Wind orientation continues to be variable, so expect new and old wind slabs to be distributed across a wide range of aspects.
Use ridges or ribs to avoid pockets of wind loaded snow.Don't let human factors push you into the wrong terrain while avalanche danger is elevated.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very 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 wrong location may have the ability to trigger a deeply buried weak layer.
Stiff cornices can easily pull back into flat terrain at ridgetop if they fail.Falling cornices may trigger large avalanches on the slopes below.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

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