Avalanche Forecast

Issued: Dec 25th, 2014 8:40AM

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

swerner, Avalanche Canada

South Columbia.

Conservative decision making and terrain use is the name of the game when these tricky avalanche conditions persist. Check out the new Forecaster Blog @ avalanche.ca.

Summary

Confidence

Good

Weather Forecast

A ridge of high pressure is strengthening a predominant northwesterly flow which will invade the Interior regions. This will bring relatively dry cool air. Ridgetop winds will blow light-moderate from the northwest and alpine temperatures will hover near -12. Skies will likely remain cloudy with some sunny periods Friday and Sunday. Light precipitation is expected Saturday.

Avalanche Summary

On Wednesday, several natural avalanches up to size 2 were reported and results up to size 3.5 were seen with the use of explosives. The buried surface hoar layer remains very touchy to skier/ rider triggers and numerous avalanches size 1-2.5 were reported. I don't expect things to improve over the holiday period and suspect this layer is primed for human triggers.

Snowpack Summary

New snow 10-30 cm fell Tuesday night. In some parts of the region the new snow is sitting on a thin breakable rime crust, but most concerning is the thick persistent slab (40-90 cm) which is sitting on a very touchy surface hoar layer buried mid-December. Below 2100 m this slab sits on a thick, solid crust that has been acting as a perfect sliding layer. Persistent slabs will be very touchy to the weight of a skier and rider, especially in wind effected areas where the slab is stiffer. A hard rain crust with facets from early November is buried over 1 m down and is currently unreactive but triggering from shallow rocky, unsupported terrain remains a concern.

Problems

Persistent Slabs

A very touchy surface hoar layer is buried by a 40-90 cm thick persistent slab. This layer is widespread, and is easily triggered by skiers and riders. Remote triggering with wide propagation is a concern.

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

Deep Persistent Slabs

A hard rain crust buried 1-1.5 m down seems to be unreactive, however; likely trigger spots are thin rocky and unsupported terrain, or from shallow snowpack areas.

Avoid shallow snowpack areas where triggering is more likely.>Be aware of thin areas that may propogate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

3 - 6

Valid until: Dec 26th, 2014 2:00PM