Avalanche Forecast

Issued: Dec 20th, 2015 8:20AM

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

jlammers, Avalanche Canada

Purcells.

Extensive wind effect has likely occurred at higher elevations. The best (and safest) riding may be found on sheltered slopes at treeline and below.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Light flurries (no more than 3 cm each day) are expected for all 3 days of the forecast period. Moderate southwest ridgetop winds forecast for Monday and Tuesday will ease to light and westerly by Wednesday. The freezing level should sit at valley bottom for the foreseeable future. For a more detailed weather discussion, please check-out our Mountain Weather Forecast at: avalanche.ca/weather.

Avalanche Summary

Observations were limited on Saturday and Sunday; however, an explosive-controlled size 2 wind slab was observed on a north-facing alpine slope. Continued strong winds and new snow from Sunday will likely be the driver for human-triggered wind slab avalanche activity over the next few days.

Snowpack Summary

Recently formed wind slabs can be found at treeline and in the alpine. Between 40 and 80cm below the surface you'll likely find a layer of weak buried surface hoar which is most prominent between 1400m and 1800m although it may extend higher in the mountains south of Invermere. Snow pit tests suggest that human triggering of this interface is becoming unlikely, although a release at this interface could be destructive in nature. Below this, the snowpack is thought to be mainly well settled.

Problems

Wind Slabs

Recently formed wind slabs may still be sensitive to human triggering. The best and safest skiing may be on sheltered slopes at lower elevations.

Be cautious as you transition into wind affected terrain.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

A layer of buried surface hoar can be found between 1400m and 1800m. Although this layer has become less likely to trigger, I'd remain cautious on steep roles in cut-blocks and open glades below treeline.

Conditions have improved, but be mindful that buried persistent weaknesses are still present.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Dec 21st, 2015 2:00PM