Avalanche Forecast

Issued: Dec 22nd, 2015 7:54AM

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.

Conditions are expected to improve over the forecast period. Make observations continually as you travel.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

A benign yet cool weather pattern has set up and will continue for the forecast period. For each day, expect a mix of sun and cloud with isolated flurries, although slightly higher accumulations are possible in the far south of the region. Ridgetop winds are expected to remain light while alpine temperatures should remain between -12 and -16.

Avalanche Summary

Evidence of a few natural wind slab avalanches to size 2 was observed in lee alpine terrain on Monday and Tuesday. The avalanches occurred in response to new snow and wind on the weekend.

Snowpack Summary

Throughout last weekend there was up to 20cm of new snow. Strong southerly winds have redistributed much of this snow into soft wind slabs in exposed lee features in the alpine and at treeline. 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.

Problems

Wind Slabs

Recently formed wind slabs have become less likely to trigger. That said, I'd remain cautious in high elevation lee terrain where wind slabs may still be sensitive to light inputs such as skiers or riders.

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.

Likelihood

Possible

Expected Size

1 - 2

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 are greatly improved, but be mindful that persistent weak layers are still present.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Dec 23rd, 2015 2:00PM