Avalanche Forecast

Issued: Dec 27th, 2014 8:11AM

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

Avalanche Canada triley, Avalanche Canada

A persistent weak layer of buried surface hoar is the sliding layer for human triggered avalanches. This problem results in the avalanche danger staying up at Considerable for the forecast period.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

5-10 cm of dry light snow is expected overnight combined with light Northwest winds, alpine temperatures around -12 and freezing levels at valley bottoms. Another 5-10 cm of light snow is expected during the day on Sunday combined with light Northerly winds and alpine temperatures around -15. Gradual clearing during the day on Monday as the ridge of High pressure builds and arctic air descends from the North resulting in alpine temperatures around -20. Continued clear and cold on Tuesday.

Avalanche Summary

A skier remotely triggered a size 1.5 avalanche in the Southern Monashees that released on the mid-December buried surface hoar. A snowcat remotely triggered two large avalanches that were about 50 cm deep on Northeast aspects at treeline in the Selkirks. There was also one natural size 2.0 in the Selkirks reported that appeared to have released on the mid-December surface hoar. This activity was from Friday. An early report from one operator on Saturday described remotely triggering several avalanches up to size 2.5 that were releasing down 45-60 cm on the buried surface hoar between 2200-2450 metres elevation.

Snowpack Summary

5-15 cm of light dry new snow has been added to the recent storm slab. In some parts of the region a thin breakable rime crust exists between the new snow and the storm slab. The upper 40-90 cm of storm snow is slowly consolidating into a slab above a touchy surface hoar layer buried mid-December. Below 2100 m this slab sits on a thick, solid crust/ surface hoar combo and acting as a perfect sliding layer. Persistent slabs will be touchy to the weight of a skier and rider, especially in wind effected areas where the slab is stiffer. Deeper in the snowpack is a hard rain crust with facets from early November. This is buried over 1 m down and is currently unreactive but triggering from shallow rocky, unsupported terrain remains a concern.

Problems

Persistent Slabs

An icon showing Persistent Slabs
The 50-70 cm deep slab continues to be triggered from steep convex rolls and adjacent terrain. The forecast cooling is expected to help preserve the buried weak layer, resulting in this problem persisting through the Holidays.
Use conservative route selection, dig down and test weak layers before committing to anything.>Stick to simple terrain, small features with limited consequence and be aware of what is above you at all times.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 5

Valid until: Dec 28th, 2014 2:00PM