Avalanche Forecast

Issued: Jan 16th, 2013 9:17AM

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

Thursday: Light W winds. Alpine temperature near -2. Freezing level is at valley bottom, with alpine inversions possible (parcels of warm air which could bring relatively warm alpine temperatures). No snow.Friday: Light NW winds. Alpine temperature near -9. No snow.Saturday: Light to moderate SW winds. Alpine temperature near -1. 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 north to north-westerly winds have left wind slabs in many areas, even at treeline. Settled storm 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. 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.

Be cautious as you transition into wind affected terrain.>Be aware of the potential for wide propagations due to the presence of hard windslabs.>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 can still be triggered by the weight of a person or snowmobile.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Be cautious on steep southerly aspects, where a buried crust/facet layer may be most reactive.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 5

Valid until: Jan 17th, 2013 2:00PM