Avalanche Forecast

Issued: Mar 6th, 2014 5:28PM

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

jon stuart-smith, Parks Canada

Waterton Lakes.

Skiing has improved and warm temps are helping settle the snowpack. More snow, winds and a rise in freezing level are forecast for Sunday. Avalanche danger will increase with these changing conditions so use conservative terrain choices.

Summary

Weather Forecast

Isolated flurries are forecast for Fri and Sat with the freezing level around the 1700m mark. Another system is forecast to arrive on Sun that could bring another 10-15cm with the freezing level rising to 2000m. Winds will increase from moderate on Fri to strong, gusting over 100km/hr Sun.

Snowpack Summary

Rain to 1800m yesterday with cold air moving in from valley bottom. 35-55cm now sits on a buried crust on solar aspects and isolated windslabs found at treeline and above. Between 70 and 150cm now buries the weak February facet layer. Large avalanches will result if this layer is triggered given the demonstrated ability of this slab to propagate.

Avalanche Summary

A loose wet avalanche occurred on Wednesday during the rain event. Numerous sz 2 avalanches have been reported in this weeks storm snow in the surrounding areas. Rapid loading from the forecast wind and snow on Sunday along with freezing level forecast to reach 2000m may result in significant avalanche activity.

Confidence

Intensity of incoming weather systems is uncertain

Problems

Storm Slabs

Up to 55cm of new snow has arrived over the last week. Warm temperatures are helping it settle but it is siting on a variety of sun crust, old windslab or facets. Warm temps on Sun could provide a trigger for this layer.

The new snow will require several days to settle and stabilize.Pay attention to overhead hazards like cornices.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Wind Slabs

Moderate to strong westerly winds have been building windslabs on lee slopes below ridge crests in the alpine and at treeline. These will continue to build over the next few days. Expect to encounter slabs as you enter open terrain.

Use caution in lee areas. Recent wind loading have created wind slabs.Avoid freshly wind loaded features.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

These slabs became less sensitive with the increasing snowpack depth. As temperatures warm to ridgetop for Sun limit your exposure to significant slopes. Do not get taken by surprise. Long propagations may still be possible.

Dig down to find and test weak layers before committing to a line.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely

Expected Size

1 - 3

Valid until: Mar 9th, 2014 5:00PM