Avalanche Forecast

Issued: Feb 27th, 2017 4:43PM

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

Avalanche Canada swerner, Avalanche Canada

Cranking winds accompanied by 5-10 cm will likely build new and reactive wind slabs at upper elevations. Deeper slabs may exist on leeward slopes.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

A change in the weather pattern is upon us as the jet shifts to a westerly flow allowing a series of Pacific frontal systems to track across the Interior Coastal Region.Tuesday: Mix of sun and cloud with a trace of new snow 5-8 cm. Alpine temperatures near -9 and ridgetop winds moderate with strong gusts from the SW. Wednesday: Cloudy with scattered flurries. Alpine temperatures near -10 and ridgetop winds moderate with strong gusts from the SW. Thursday: Mostly cloudy with a trace of new snow. Alpine temperatures high of -4 and ridgetop winds moderate-strong from the West. Freezing levels rising to 1000m.

Avalanche Summary

On Sunday, numerous natural wind slabs were reported up to size 1.5 which were triggered by the recent wind event. Previously, there was a report of a size 2.5 natural avalanche in the northern part of the region. This may have happened in the last 5 days and possibly failed on a persistent weak layer buried early february on a NW aspect in the alpine.

Snowpack Summary

Up to 20 cm of storm snow accumulating in the last week has been transported by the wind, and now sits on a variety of old surface conditions including isolated wind slabs, pockets of soft snow (5 to 10 cm deep), sun crusts, and surface hoar. A supportive rain crust exists below 1000 m. A layer of surface hoar that was buried on February 10th may exist 30 to 60 cm below the surface, but there's a fair bit of uncertainty regarding the reactivity and distribution of this layer. A stiff mid pack sits above weak sugary snow near the ground. Although possibly dormant, this basal weakness has the potential to produce very large destructive avalanches.

Problems

Wind Slabs

An icon showing Wind Slabs
Changing wind directions may form new wind slabs on N-NE aspects. Old wind slabs may continue to linger on southerly aspects due to the recent outflow winds.
Be cautious as you transition into wind affected terrain.Use ridges or ribs to avoid pockets of wind loaded snow.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
A lingering weakness at the bottom of the snowpack may remain sensitive to human triggering, especially in shallow snowpack areas. Surface avalanches in motion also have the potential to step down and trigger deep persistent slabs.
Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 4

Valid until: Feb 28th, 2017 2:00PM

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