Avalanche Forecast

Issued: Feb 12th, 2013 3:00PM

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

Avalanche Canada pmarshall, Avalanche Canada

Summary

Confidence

Good

Weather Forecast

Wednesday: Light snow early then a mix of sun and cloud. The freezing level is around 1200 m. Winds are light to moderate from the northwest. Thursday: A mix of sun and cloud. The freezing level is near valley bottom. Winds are light from the northwest. Friday: A mix of sun and cloud. The freezing level could jump as high as 1400 m. Winds are light to moderate from the southwest.

Avalanche Summary

On Monday there were also a few natural and rider triggered slab avalanches up to size 2 from recently wind loaded features in the alpine (NE-SE aspects). There were also a few reports of natural cornice failures that triggered slab avalanches up to size 2. There was one report of a remotely triggered size 1.5-2 avalanche from the Monashees. It was actually 2 avalanches. Both were triggered from flat terrain. One released above and one released below the group but no one was involved.

Snowpack Summary

The snow surface consists of new wind slab in exposed alpine terrain, a sun crust on solar aspects, and surface hoar and/or facets on shady slopes. Below this 20-40 cm of settled storms snow sits on a surface hoar and sun crust layer that developed at the beginning of February. This layer continues to be reactive to rider triggers. Deeper down (between 40-80 cm) sits an old sun crust and well preserved surface hoar that was buried on January 23rd. This persistent slab has been reactive and easily triggered over the past few days, especially from solar aspects and at treeline and below treeline over steeper convex slopes. During recent snowpack testing this layer has shown moderate compression results with sudden planar to resistent planar characteristics. This layer is getting stronger over time and less likely to trigger, but if triggered it will still produce a significant avalanche. The mid-pack is generally well settled and strong.

Problems

Wind Slabs

An icon showing Wind Slabs
Wind slabs exist on lee slopes and behind terrain features like ribs and ridges. Be cautious in steep unsupported terrain near ridge top.
Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
Persistent slabs are 40-80 cm thick and continue to be reactive above variable sliding surfaces comprising of surface hoar, crusts and facets. They may be triggered by the weight of a skier or a machine.
Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Feb 13th, 2013 2:00PM

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