Avalanche Forecast

Issued: Jan 19th, 2015 4:12PM

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

ian jackson, Parks Canada

Banff Yoho Kootenay.

Parks Canada is planning Avalanche Control on Mt. Dennis for Tuesday January 20. No ice climbing or travel in this area please. TH

Summary

Weather Forecast

Temperatures should cool, and skies should clear as the winds shift to the NW Tuesday under the influence of a high pressure system. A series of lows will be pushed well North as a result of this high but clouds should return mid day Wednesday with increasing winds, a chance of light snow arriving overnight, and temperatures rising into Thursday.Â

Snowpack Summary

At Treeline and above, 15 to 25cm of recent snow with west winds has created slabs on facets, surface hoar, sun crust on steep South slopes and hard windslabs along ridge crests Treeline and above. In general the snowpack is weak with well developed faceting at the Dec 18 interface down 35 to 50cm and depth hoar commonly seen in the bottom 30cm.

Avalanche Summary

On an avalanche control flight today to the Sunshine road, 8 of 9 shots produced significant avalanches and 3 natural avalanches were observed. Most of these initiated in the recent storm slabs 20 cm deep but several also stepped down to the Dec 18 interface to a depth of 50cm. Crowns were as wide as 150m and several events ran up to 1km.

Confidence

Problems

Wind Slabs

New windslabs 20 to 40cm deep can be found in almost any lee areas including crossloaded features. These slabs are easily triggered and some the resulting avalanches have been stepping down to the Dec 18 persistent slabs.

Avoid freshly wind loaded features.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 2

Persistent Slabs

In shallower snowpack areas this layer has been facetting out however in deeper areas where a stronger slab exists above, this layer remains more of a concern.

Watch for whumpfing, hollow sounds, and shooting cracks.Minimize exposure to overhead avalanche terrain, large avalanches may reach run out zones.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Deep Persistent Slabs

In shallower snowpack areas (most of the region) the weak base of the snowpack persists and could be triggered in steep, rocky terrain features. This problem will persist for some time, give it careful consideration before entering serious terrain.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Avoid thin, rocky or sparsely-treed slopes.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Jan 20th, 2015 4:00PM