Avalanche Forecast

Issued: Mar 23rd, 2016 4:00PM

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

Lisa Paulson, Parks Canada

Banff Yoho Kootenay.

Although the danger is rated MODERATE - this means that natural avalanches are not expected, but HUMAN TRIGGERED AVALANCHES ARE POSSIBLE. Conditions remain tricky despite seeing less avalanches happening. The ones that do happen are huge!

Summary

Weather Forecast

Overcast skies and light snow forecast for Thursday with temperatures remaining in the -2 to -7 range as long as the sun doesn't come out, and light winds. This time of year it only takes a short burst of strong sun to have an influence on the snowpack - but right now it looks like Thursday will be a pretty benign day in the mountains.

Snowpack Summary

Surface crusts exist in most locations except shaded terrain above 1850 m. Shallow snowpack areas remain weak with our focus on facets in the lower snowpack overlain by a stiff slab. Tests on these facets produce easy, sudden collapses. Buried crusts in the upper meter are also a concern, and have been producing avalanches within the past week

Avalanche Summary

Over the past week there have been reports large avalanches triggered by cornice failure, explosive or human. Of note was the large human triggered avalanche in Kananaskis Country last Sunday involving a thick hard slab over weak depth hoar. Similar results can be expected in the our region, which is adjacent. Human triggering remains possible.

Confidence

Due to the quality of field observations

Problems

Deep Persistent Slabs

Deep facet layers remain very weak, especially in thin or rocky areas. Avoid large open slopes, steep slopes (>30 degrees) and be wary that you can trigger this problem from a long distance away - the slab is stiff and it propagates far.

Avoid steep convexities or areas with a thin or variable snowpack.Watch for signs of instability such as whumpfing, or cracking.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Persistent Slabs

Avalanches on buried crusts with facets have been seen on sun exposed slopes within the last few days. Presently there are several crusts buried with 40-100 cm overlying them.

Dig down to find and test weak layers before committing to a line.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Cornices

Cornices are large, and warm temperatures make them weak. Ensure you give them a wide berth on ridge crests, as they can pull back a long way when they fail and may trigger avalanches below. If you need to travel under cornices - move quickly.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3

Valid until: Mar 24th, 2016 4:00PM