Avalanche Forecast

Issued: Feb 26th, 2012 9:12AM

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

pgoddard, Avalanche Canada

South Columbia.

Local areas receiving direct sunshine may spike to HIGH danger.

Summary

Confidence

Good

Weather Forecast

Monday: Mainly clear and sunny, with valley cloud. No precipitation. Light westerly winds. Freezing level valley floor. Tuesday/Wednesday: Flurries possible on western slopes. Light-moderate south-westerly winds. Becoming slightly milder.

Avalanche Summary

Many large natural and human-triggered avalanches have been reported each day since Wednesday. Natural activity (up to size 3.5) spiked following the heaviest snowfalls on Tuesday night and Friday night. Skiers have been triggering avalanches (mostly size 1-2.5) accidentally and remotely. These are running on storm snow instabilities or persistent weaknesses in the upper snowpack. There have been some lucky escapes. Conditions will remain ripe for human-triggering after the more obvious signs of instability (like new snowfall, wind-loading and natural activity) die down.

Snowpack Summary

Deep wind slabs exist on many aspects at all elevations. Storm snow totals range from about 60-140cm above the Feb 16. surface hoar layer and the Feb. 8 interface. The Feb. 8 interface is a combination of weak layers: in most locations it marks a widespread surface hoar layer. On steep south- and west -facing aspects, a sun crust that formed during the drought was also buried on Feb. 8th. This crust probably has a bit of faceting below it too, meaning that most terrain in the region has a weak layer in the upper snowpack. Recent remote and natural triggering indicates the touchy nature of these weaknesses. Large cornices threaten many slopes.

Problems

Persistent Slabs

Several weaknesses exist in the upper snowpack, now buried by about 1m of snow. These layers are very sensitive to triggers and pose the threat of large, destructive avalanches which could be triggered by the weight of a person.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

2 - 6

Wind Slabs

Wind slabs have grown large on many slopes. Persistent weak layers are buried beneath these slabs, meaning they could be touchy and create very large avalanches. Large cornices also threaten many slopes.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Valid until: Feb 27th, 2012 8:00AM