Avalanche Forecast

Issued: Jan 15th, 2013 9:33AM

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 weather conditions

Weather Forecast

Wednesday-Friday: Moderate to strong north-westerly winds. Freezing level is at valley bottom, with alpine inversions possible (parcels of warm air which could bring alpine temperatures close to 0). Light snow is possible on Wednesday.

Avalanche Summary

Avalanche activity has begun to slow, but occasional skier-triggered avalanches are still being reported, failing on persistent weak layers from early January. Many of these events were on SE through SW aspects, with the odd persistent slab on other aspects. Some solar-related and loose dry natural activity was observed on Monday.

Snowpack Summary

North to north-westerly winds have left wind slabs in the lee of terrain breaks such as ridges and ribs at alpine and treeline elevations. Recent storm snow is settling over old snow surfaces including 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 is still possible to trigger a large avalanche with the weight of a person or snowmobile. Watch out for rapid warming on alpine slopes over the next couple of days, which could weaken the slab above these interfaces. 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.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Use ridges or ribs to avoid pockets of wind loaded snow.>Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Persistent Slabs

Persistent weaknesses are variable in their distribution but can still be triggered by the weight of a person or snowmobile. Triggering persistent slabs will become more likely if the snowpack experiences rapid warming.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Avoid convexities or areas with a thin or variable snowpack.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 5

Valid until: Jan 16th, 2013 2:00PM