Avalanche Forecast

Issued: Feb 21st, 2016 5:43PM

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

tim haggarty, Parks Canada

Banff Yoho Kootenay.

Despite the fact that temps have dropped the structure of the snowpack is so poor that human triggering still remains likely. Stay in conservative terrain and minimize your exposure to large avalanche terrain.

Summary

Weather Forecast

After a cooler day Sunday and some strong solar input, two weak fronts will reach the divide Monday bringing trace amounts of precip. Winds should remain light westerly. Overnight Monday a strong ridge will start to move into the area, skies will clear by midday Tuesday and winds shift to the North. Temperatures will drop but the sun will be strong

Snowpack Summary

Fresh windslabs and cornice growth in the alpine with 30 to 50 cm since the warming a week ago. A 50-100 cm slab overlies the January 6th weak layer of surface hoar, facets and sun crust and snowpack tests indicate an unstable bond between the two. The lower snowpack is facetted and quite weak in thinner areas but is more settled in thicker areas.

Avalanche Summary

A lot of human triggered activity occurred yesterday with a size 3 triggered form the South ridge of Bow Peak being the most eye catching. This event had a crown up to 1.5 m deep,450m wide failing below the cornice at 2600m on the E aspect. An upper slab ran about 250m but one flank continued 1.1km stopping at 1900m. The persistent slab in action..

Confidence

Problems

Persistent Slabs

50-100 cm of snow overlies the Jan 6th layer of surface hoar, facets and sun crust. Numerous avalanches triggered on this Saturday. In thinner areas, many of these avalanches have scrubbed through the facets to the ground.

Avoid paths that have not avalanched recently.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3

Wind Slabs

Be mindful of cross loaded features and the lees of ridges where moderate to strong W winds have recently formed windslabs 10-40+ cm thick and developed fragile cornices. Failures of these have stepped down to the persistent weak layer and ground.

Use caution in lee areas. Recent wind loading has created wind slabs.Minimize exposure to overhead avalanche terrain, large avalanches may reach run out zones.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Feb 22nd, 2016 4:00PM