Avalanche Forecast

Issued: Apr 4th, 2014 4:47PM

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

Lisa Paulson, Parks Canada

Banff Yoho Kootenay.

Cornices have grown and are touchy - Several natural failures observed in past 2 days with snow volumes up to size 2. Keep an eye on overhead hazard. Best skiing on due North aspects. Avoid thinner snowpacks where basal facets can be triggered.

Summary

Weather Forecast

Mainly cloudy along the Continental Divide and mix of sun and cloud East of the Divide. Winds to remain moderate with strong gusts from the West.Â Freezing levels to remain at valley bottom, but start to rise Monday night.Â Watch for solar related avalanche activity or cornice failures, especially on Sunday.

Snowpack Summary

New wind slabs 15-25 cm thick in the immediate lees. Western areas such as Emerald and Field have a deep and stable snowpack. Contrast this with the Lake Louise, Hwy 93 N, & Sunshine areas, where a there is a weaker snowpack with sudden collapse very easy compression results on the basal depth hoar. A crust exists on all but N aspects.

Avalanche Summary

Everyday for the past week, there have been avalanches, size 2-3 or large whumphs failing on the facets at the base of the snowpack. They were triggered by cornice, explosive, skier, or prolonged periods of sun. These observations were in the Lake Louise, Hwy 93N, and shallow areas in KNP. Several cornice failures to size 2 observed in past 2 days.

Confidence

Problems

Deep Persistent Slabs

Very low confidence in this basal layer of depth hoar as daily avalanches size 2-3 and large whumphs continue to be reported. Mainly a problem on the East side of the Continental Divide or in shallower snowpacks in Kootenay Park.

Avoid shallow snowpack areas where triggering is more likely.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Wind Slabs

Wind slabs 15-25 cm thick were found in immediate lee terrain and failed easily in snowpack tests.

Use caution in lee areas. Recent wind loading have created wind slabs.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Apr 5th, 2014 4:00PM