Avalanche Forecast

Issued: Feb 15th, 2012 9:00AM

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

Avalanche Canada istorm, Avalanche Canada

Summary

Confidence

Good

Weather Forecast

The general pattern of a dominating high pressure ridge with weak disturbances passing through continues. Thursday should see strong NW or W winds, and a few cm of snow late in the day. Friday should be sunny & warm in the afternoon, well below freezing overnight. Saturday another disturbance is expected with a few more cm of snow and freezing level around 1000m.

Avalanche Summary

Only small avalanches were observed, mostly loose snow in steep terrain (I'm guessing solar triggered) and small slabs lee of ridges (but these are likely a day or two old). Loose surface snow may be susceptible to sluffing on steep slopes but shouldn't be too destructive unless terrain traps are in the runout. Deep persistent slab avalanches remain possible with heavy triggers in shallow rocky snowpack areas on unsupported slopes.

Snowpack Summary

On sunny slopes (SE, S, or around toward W facing slopes) Wednesday's sun created a crust. On shady slopes a new layer of surface hoar formed overnight Tuesday. Also on shady slopes immediately below the surface (hoar) is 5 to 10 cm of recent snow sitting on a second surface hoar layer, which in turn sits on sugary facetted snow. One report showed the feathery crystals of surface hoar around 4 cm long. All the crusts and surface hoar will need watching once it snows. Below these upper layers a well settled and strong snowpack sits on weak basal facets and depth hoar, which seem to be fairly widespread throughout the region. This deep persistent weakness was recently activated by warm temperatures, but cooler temperatures have once again reduced the sensitivity to triggers. Highly unpredictable glide cracks are also opening up, primarily on slopes with smooth ground cover. These full-depth gaping 'crevasses' could release without warning or act as a significant terrain trap.

Problems

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Deep and destructive persistent slab avalanches are unlikely, but a large trigger may activate this weakness on a steep, rocky & unsupported area with a shallow snowpack.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely

Expected Size

3 - 6

Wind Slabs

An icon showing Wind Slabs
Although thin, fresh wind slabs could quickly become twitchy where they devolop above a suncrust.

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Cornices

An icon showing Cornices
Cornices are large, unsupported and may be a trigger for a large avalanche on the slope below.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Valid until: Feb 16th, 2012 9:00AM