Avalanche Forecast

Issued: Dec 19th, 2015 8:36AM

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

jlammers, Avalanche Canada

Purcells.

New snow and strong winds on Sunday will keep the Avalanche Danger elevated. Watch for new wind slabs.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Sunday

Weather Forecast

Between 5 and 15cm of new snow and strong to extreme southwest ridgetop winds are expected on Sunday. Continued light flurries and moderate southwest winds will persist for Monday and Tuesday. Freezing levels should sit at valley bottom for all 3 days. For a more detailed weather overview, check out our Mountain Weather Forecast at avalanche.ca/weather.

Avalanche Summary

Observations were limited on Saturday; however, an explosive-controlled size 2 wind slab was observed on a north-facing alpine slope. Continued strong winds and new snow will likely be the driver for continued 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

Even if new snow amounts are modest in your riding area, there's plenty of loose snow on the ground for redistribution by forecast strong winds on Sunday. Watch for new wind slab development at treeline and in the alpine.

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

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

A layer of buried surface hoar can be found between 1400m and 1800m. Use increased caution on steep roles on cut-blocks and in open glades below treeline.

Avoid open slopes, convex rolls, burns, cutblocks and terrain traps when traveling below tree-line. This is where buried surface hoar is best preserved and most volatile.>Conditions have improved, but be mindful that buried persistent weaknesses are still present.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Dec 20th, 2015 2:00PM