Avalanche Forecast

Issued: Dec 10th, 2012 9:15AM

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

pgoddard, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain for the entire period

Weather Forecast

Monday night: Expect winds of up to 100 km/h from the SW and about 20 cm of snow overnight. Alpine temp -5.Tuesday: Westerly winds dropping to moderate. Alpine temp -6. Light snow. Freezing level 800 m, dropping to surface overnight.Wed: Light westerly winds. Alpine temp -7. Freezing level 100 m. Light snow.Thurs: Moderate SW winds. Alpine temp -3. Freezing level 800 m. 5 cm snow.

Avalanche Summary

On Sunday, natural activity to size 2.5 occurred in response to very strong winds, new snow and warming. This cycle is expected to continue through Monday and Tuesday.

Snowpack Summary

Storm snow is being redistributed by very strong winds, creating wind slabs on a variety of slopes. In sheltered areas below treeline, loose sluff may be encountered. New wind slabs may be sitting above widespread surface hoar, making a touchy combination. The surface hoar was particularly noticeable in the Shames backcountry on Saturday. In general the mid-pack is gaining strength. A November facet/crust layer can be found near the base of the snowpack. Observations of this layer are limited, however recent explosives testing suggests it may be more problematic in the north of the region than in the south. Above about 1000 m, the snowpack is 150-200 cm deep. Below 1000 m, the snowpack is only just reaching threshold.

Problems

Wind Slabs

Widespread wind slabs are likely to be found on alpine slopes and behind ridges and ribs at treeline and below.

Avoid freshly wind loaded features.>Be aware of the potential for wide propagations due to the presence of hard windslabs.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Deep Persistent Slabs

A deeply buried facet/crust weakness exists. While the likelihood of triggering it is low, the consequences could be a very large and destructive avalanche.

Avoid shallow snowpack areas where triggering is more likely.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 7

Valid until: Dec 11th, 2012 2:00PM