Avalanche Forecast

Issued: Feb 27th, 2012 9:15AM

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.

Avalanche Canada pgoddard, Avalanche Canada

In your local area: Be wary of any slopes which are being warmed by direct sun, as this may weaken existing slabs and could cause natural avalanches.

Summary

Confidence

Good

Weather Forecast

Tuesday: Mainly sunny with valley cloud. Light southerly winds. Freezing level around 600m. Wednesday/Thursday: Cloud and flurries. Light south-west winds. Temperatures remain cool, except during sunny breaks, when some local solar warming may occur.

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

Recent storm snow totals of about 60-140cm sit above the Feb 16. surface hoar layer and the early Feb interface. The early Feb 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 was also buried at the same time, meaning that most terrain in the region has a weak layer in the upper snowpack. Deep wind slabs exist on many aspects and cornices are large. Upper snowpack persistent weak layers are still very touchy, as evidenced by scores of remote and human-triggered avalanches over the past several days. Cornice fall and solar warming are my top current picks for further natural triggering of these weak layers, while human/machine-triggering remains likely on a variety of slopes.

Problems

Persistent Slabs

An icon showing Persistent Slabs
Several weaknesses exist in the upper metre or so of the snowpack. These layers remain sensitive to triggers. Large, destructive avalanches could be triggered by the weight of a person, even from a distance.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

2 - 6

Wind Slabs

An icon showing 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

Expected Size

1 - 5

Valid until: Feb 28th, 2012 8:00AM