Avalanche Forecast

Issued: Jan 12th, 2013 8:38AM

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

Avalanche Canada pmarshall, Avalanche Canada

Summary

Confidence

Good

Weather Forecast

Sunday: Mainly sunny with cloudy periods in the afternoon. Temperatures should remain cool with alpine highs near -6. Winds are moderate from the northwest. Monday: Mainly sunny with possible valley fog. An above freezing level develops through the day between 1500 and 2500 m. Winds are moderate to strong from the northwest. Tuesday: Mainly sunny with possible valley fog. The above freezing layer strengthens with alpine temperatures rising to +5. Winds are moderate to strong from the northwest.  

Avalanche Summary

There was a size 2 accidentally triggered slab avalanche in the Spearhead Range on Thursday. A thin wind slab was triggered near ridge top on a relatively low-angle slope, which then stepped down to a weak layer approximately 100 cm deep lower on the slope. This avalanche is suspected to have released on the early January surface hoar layer.

Snowpack Summary

The snow surface consists of thin new wind slabs, a sun crust, dry snow, or feathery surface hoar depending on aspects and elevation. Below this 40-70 cm of storm snow sits on a weak layer of surface hoar, facetted snow, and/or a crust. Snowpack tests on Wednesday continued to yield easy to moderate sudden planar, or "pops", results on this interface. No significant weaknesses have been reported recently below this in the mid snowpack layers. Near the base of the snowpack, a crust/facet layer exists, which is now unlikely to be triggered, except perhaps by heavy triggers in steep, shallow, rocky terrain where more facetting has taken place.

Problems

Persistent Slabs

An icon showing Persistent Slabs
It may be possible to trigger avalanches that release on a weak layer of surface hoar or facetted snow down 40-70 cm.
Be wary of slopes that did not previously avalanche - even on low angle terrain.>Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Choose conservative lines and watch for clues of instability.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 5

Wind Slabs

An icon showing Wind Slabs
Northerly winds have created thin pockets of wind slabs in lee and cross-loaded terrain features, while older buried wind slabs exist on exposed north facing slopes.
Avoid freshly wind loaded features.>Highmark or enter your line well below ridge crests to avoid wind loaded pillows.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

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

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