Avalanche Forecast

Issued: Dec 19th, 2014 7:24AM

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

pgoddard, Avalanche Canada

Purcells.

New snow, strong winds and rising temperatures make a good recipe for rising avalanche danger over the next few days.

Summary

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

Expect light to locally moderate snow from Saturday to Monday. Temperatures rise towards 0 at 1500m by Saturday. Winds are expected to be moderate to strong from the west to south-west throughout the period.

Avalanche Summary

On Thursday and Friday, explosive control produced several size 1-2 slabs. These slabs were around 20cm thick. In the Dogtooth area, these failed on reloaded bed surfaces (early November rain crust/facet layer). A size 2.5 naturally-triggered slab was observed at 2600m on an east aspect on Friday.

Snowpack Summary

New snow sits on variable surfaces including wind-affected snow, surface hoar and a crust which exists below about 2200m. Winds are expected to shift new snow onto lee slopes over the next couple of days. A thick rain crust with facets from early November is buried over 1 m down and may still be reactive in isolated areas. A weak layer from the end of November sits in the middle of the snowpack and is still reactive in some areas.

Problems

Storm Slabs

Storm snow is expected to be shifted by winds into slabs on lee slopes. In more sheltered areas, loose snow avalanches may be encountered in steep terrain. The new snow sits above a weak layer of buried crystals in some locations.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Deep Persistent Slabs

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

Remote triggering is a concern, watch out for adjacent slopes.>Avoid common trigger zones including thin snowpack areas, near rocky outcrops, and steep alpine slopes.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Dec 20th, 2014 2:00PM