Avalanche Forecast

Issued: Feb 13th, 2015 8:43AM

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

Avalanche Canada ccampbell, Avalanche Canada

A Special Public Avalanche Warning is in effect for this region. The only worthwhile riding is likely on the least trustworthy slopes. Be circumspect on largeĀ  steep alpine slopes.

Summary

Confidence

Good

Weather Forecast

Saturday: Cloudy with possible light snow. The freezing level lowers to around 1800-2000 m. Winds are generally light from the W-NW. Sunday: Cloudy with light snow and occasional sunny breaks. The freezing level is around 1400-1500 m. Monday: Mainly sunny and dry with light winds and freezing levels around 1500 m.

Avalanche Summary

Reports from Thursday include isolated large explosive triggered persistent slab avalanches failing on the mid-January surface hoar on northeast facing treeline and alpine slopes. These slabs were 80-150 cm thick with some wind-loaded pockets as deep as 2 m. One avalanche was described as 'sluggish', but highly destructive, taking out mature timber on the way down.

Snowpack Summary

Recent warm temperatures have softened the upper snowpack, reawakening deep persistent weaknesses in isolated areas. As temperatures continue to fluctuate and stress the snowpack, expect an increased likelihood of triggering large destructive avalanches in isolated areas (e.g. thin spots) with heavy triggers (e.g. cornice falls, stuck sleds spinning tracks, or groups of people). Approximately 65-100 cm of recent storm snow is bonding well to a crust buried at the beginning of February; however, this bond is much weaker where surface hoar overlies the crust. Below that, recent snowpack tests gave moderate to hard but sudden collapse results on the mid-January surface hoar where it was found down 70-82 cm on a northeast facing treeline slope. This persistent weakness has been found as deep as 110 cm, or deeper on wind-loaded slopes. The mid-December crust/facet/surface hoar weakness may be persisting in the mid to lower snowpack at higher elevations.

Problems

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Deep persistent weaknesses recently woke up with the warm temperatures and should be treated with suspicion until after things freeze up again. Although likely to need a large trigger, the potential consequences are dire.
Be aware of thin areas that may propagate to deeper instabilities.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Storm Slabs

An icon showing Storm Slabs
Warm temperatures and sunshine could destabilize the recent snow resulting in isolated slab activity and loose wet sluffs, particulary on steep sun-exposed slopes.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 5

Cornices

An icon showing Cornices
Cornices will likely become unstable with fluctuating temperatures. Not only are they a hazard in themselves, but they are also large triggers for deep slab avalanches on the slope below.
Give cornices a wide berth when travelling on or below ridges.>Cornices become weak with daytime heating. >

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Feb 14th, 2015 2:00PM