Avalanche Forecast

Issued: Dec 20th, 2014 7:23AM

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

pgoddard, Avalanche Canada

South Columbia.

New snow, strong winds and rising temperatures make a good recipe for rising avalanche danger.

Summary

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

Light to locally moderate snow is expected in pulses from Sunday to Tuesday. The heaviest snowfall is expected overnight Saturday/Sunday (15-40 cm) and should be accompanied by moderate to strong westerly winds. Freezing levels are expected to be around 1500m on Sunday, gradually dropping to near 800m by Tuesday.

Avalanche Summary

In areas which have already received 30 cm or more of storm snow above the surface hoar/crust interface, skiers were easily triggering slabs to size 1.5 on Friday (including one remote trigger with a partial burial). Other parts of the region may be slightly below the 'tipping point' today, but should have reached it by Sunday. I expect very touchy conditions on Sunday, with natural activity likely overnight Saturday and skier triggering of storm slabs likely on Sunday.

Snowpack Summary

Storm snow and wind slabs are building up. These are bonding poorly to a layer of large surface hoar crystals. Below around 2100m, this surface hoar sits on a hard rain crust. Above 2100m the surface hoar sits on well settled and faceted snow. A thick rain crust with facets from early November is buried over 1 m down and may still be reactive in isolated areas.

Problems

Storm Slabs

Avalanche activity has already begun in some parts of the region as storm snow builds up over a touchy weak layer. Winds are likely to concentrate slabs on lee slopes in wind-exposed areas.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Be cautious of sluffing in steep terrain.>Avoid freshly wind loaded features by sticking to ridges and ribs.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Deep Persistent Slabs

There is still the potential to trigger a deeply buried weak layer, resulting in a surprisingly large avalanche.

Avoid shallow snowpack areas where triggering is more likely.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 6

Valid until: Dec 21st, 2014 2:00PM