Avalanche Forecast

Issued: Dec 29th, 2011 9:53AM

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

swerner, Avalanche Canada

South Rockies.

Summary

Confidence

Fair - Intensity of incoming weather is uncertain on Friday

Weather Forecast

Friday: Snow amounts 5-10cms. Ridgetop winds 75-100km/hr from the West. Freezing levels could rise to 1000m. Saturday/Sunday: A ridge of high pressure is expected to move into the region for the weekend. Mainly sunny skies, and light-moderate winds from the West. Temperatures at 1800m will be near -15.

Avalanche Summary

Natural activity reported today up to size 2 on steep N-NE facing slopes. Some natural low density sluffing in steep, rocky terrain features. Cornice fall on N-NE aspects initiating avalanches up to size 2.

Snowpack Summary

Strong westerly winds, up to 10cms of new snow and warmer temperatures continue forming wind slabs on lee locations. Windward aspects are being stripped, and scoured in the alpine and open treeline. A buried layer of surface hoar lies approximately 30-40cms below the snow surface. This layer is not widespread; it's quite spotty through the region. This layer may be found in isolated, sheltered locations at and below treeline and up to 30mm in size. The total snowpack depth around 1800m is 70cm. We're still dealing with a variable thin snowpack. Thin spot triggering down to the basal facets and depth hoar is still a concern. A well settled mid pack bridges over the basal weaknesses at the ground in deeper snowpack areas.

Problems

Wind Slabs

Wind slabs can be found on North-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.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

More of an issue in the northern parts of the region where the snowpack is deeper. The mid-December surface hoar layer was destroyed in wind exposed areas. I'd be suspicious of sheltered treeline locations where it may be more preserved.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 6

Valid until: Dec 30th, 2011 8:00AM