Avalanche Forecast

Issued: Jan 6th, 2012 9:43AM

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

Jlammers, Avalanche Canada

South Rockies.

Summary

Confidence

Fair - Freezing levels are uncertain

Weather Forecast

Saturday: Mostly clear skies / no precipitation / moderate southwest winds / freezing levels at surfaceSunday: Light flurries / moderate southwest winds / freezing level at 1000mMonday: Light flurries / moderate southwest winds / a possibility of freezing levels climbing as high as 2000m

Avalanche Summary

A size 2 natural was reported from the Sparwood area yesterday on a northeast aspect at 1910m. A natural size 2 avalanche was reported on Mt. Fernie yesterday at 1950m. The crown depth was 30-50cms, the width was 100m, and the running length was 500m. There were also a few relevant skier-triggered avalanches up to size 2 during the past week at least one of which ran on the weak mid-december surface hoar/facet interface.Please visit our incident report database or our regional discussion forums on our website for more details.

Snowpack Summary

The average HS (height of snow) in the Crowsnest North is 120cms and the Crowsnest South has 150cms. In the alpine and exposed slopes at treeline the windward aspects have been stripped of snow, and the lee slopes have widespread stiff wind slabs. As we move further West into the Elk Valley North the HS is an average of 130cms. The Elk Valley South sits at 170cms. Weak buried surface hoar layers can be found on North-NE slopes at treeline and below down approx. 30-40cms. In the Flathead the avg. HS is 170cms. This area also sees buried surface hoar on N-NE slopes. All snow depths indicated are at a 2000m elevation. The CAC Field team headed to Harvey Pass on Tuesday and completed a fracture line profile on a skier triggered avalanche. A stiff wind slab was triggered and stepped down 55cms to the mid-December surface hoar/facet layer. Compression tests done showed easy results with sudden planar characteristics. This shows this layer is still touchy to human triggers. The mid pack is generally well consolidated. At the bottom of the snowpack a variable facet/ crust/ facet sandwich is located with depth hoar up to size 5 below the crust, and facets size 2 above.

Problems

Wind Slabs

Wind slabs can be found on North through Southeast aspects. Cross-loading is possible on open slopes oriented parallel to the wind. You may find wind slabs further down the slope or on open wind exposed areas below treeline.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

A cohesive slab sits over a touchy surface hoar weakness buried in mid-December. This layer is still touchy and susceptible to rider triggers. Avalanches on this layer will be large, destructive and more difficult to predict.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Jan 7th, 2012 8:00AM