Avalanche Forecast

Issued: Jan 17th, 2013 8:56AM

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.

pgoddard, Avalanche Canada

South Columbia.

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Friday: Moderate to strong NW winds. Alpine temperature near -2. No snow.Saturday: Moderate to strong W winds. Alpine temperature near -2. No snow.Sunday: Light to moderate W winds. Alpine temperature near -2. No snow.

Avalanche Summary

A natural and human-triggered cycle of wind slabs to size 2 was observed on Tuesday. Solar-triggered loose snow avalanches also failed on steep sun-exposed slopes. Occasional skier-triggered avalanches have been failing on persistent weak layers from early January over the last week. These have mostly been on steep south-facing slopes or sheltered slopes below treeline.

Snowpack Summary

Strong NW through SW winds have left wind slabs in many areas, even at treeline. Around 40-60 cm settled snow sits above surface hoar (found especially at and below treeline in sheltered areas), a sun crust (on steep S to SW -facing slopes) and facets. The distribution of these weaknesses is patchy, but where they exist, it may still be possible to trigger a large avalanche with the weight of a person or snowmobile. Test results on these interfaces vary from no result to moderate, sudden results. A strong mid-pack overlies a weak facet/crust layer near the base of the snowpack, which is now considered inactive.

Problems

Wind Slabs

Wind slabs may be found behind terrain breaks such as ridges and ribs. It may be possible for a wind slab to step down to a deeper instability.

Travel on ridgetops to avoid wind slabs on 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

Likely

Expected Size

1 - 4

Persistent Slabs

Persistent weaknesses are variable in their distribution but may still be triggered by the weight of a person or snowmobile.

Be cautious on steep southerly aspects, where a facet/crust layer may be most reactive.>Be wary of open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

1 - 5

Valid until: Jan 18th, 2013 2:00PM