Avalanche Forecast

Issued: Jan 12th, 2015 4:00PM

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

tim haggarty, Parks Canada

Waterton Lakes.

With surface faceting softening the upper snowpack, some surprisingly good skiing can be found if you can avoid surface crusts. Remember to keep terrain choices conservative as triggering the Persistent Weak Layer remains a possibility for travelers

Summary

Weather Forecast

We will remain under the influence of the SW flow for the period with warm moist air trying to override the cooler air on the prairies. Clouds and trace precip are likely near the divide. By Friday a warm front associated with a low approaching the coast will bring an increase in the freezing level, stronger winds and potentially some precipitation

Snowpack Summary

Generally, with the current drought conditions the upper snowpack is faceting. Windslabs overlying softer snow are the primary surface concern. In the midpack, the Dec 13 crust is now 60 to 120cm deep and remains a serious concern as it produces planar shears within the facets above the crust. Surface crusts affect ski quality.

Avalanche Summary

Despite seeing very little activity over the last few days we observed a significant slab about 40m wide, 80 to 100 cm deep on steep north facing cliffy terrain near ridge top. This slab likely failed on the Dec 13 persistent weak layer although it may have been triggered by a smaller slab and illustrates the need for care with this layer.

Confidence

Problems

Wind Slabs

Windslabs can easily be found in most open areas over low density snow. In isolated locations these are significant: hard and thick. Test these surface slabs often with your ski poles and modify your route to manage your exposure should they fail.

If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

Continue to watch for this layer which has proven to be extremely variable. Areas where these slabs are thin should raise added concern.

Dig down to find and test weak layers before committing to a line.Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Valid until: Jan 15th, 2015 4:00PM