Archived

Avalanche Forecast

Mar 21st, 2017–Mar 22nd, 2017

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Regions: Banff Yoho Kootenay.

Large explosive triggered avalanche occurred today. The potential for very large human triggered avalanches on the weak facets remains high. Avoid exposure to overhead hazard and stick to moderate angled supported terrain to enjoy the new snow.

Weather Forecast

Flurries with warmer temperatures and freezing levels around 1900 m will continue for Wednesday before a cooling trend returns. Alpine temperatures should remain below freezing. Winds will be moderate out of the SW.

Snowpack Summary

40 to 80 cm of storm snow with SW winds in the last two weeks has helped create a thick supportive slab over the deep weak basal facet layer. Rain to 2000m on Saturday created a surface rain crust which is now frozen and covered by new snow, and saturated the lower elevation snow. Sudden collapse results in the basal facets continue in test pits.

Avalanche Summary

Natural activity to size 3+ was observed Monday in Yoho and Banff. Explosive control work today and over the last several days has produced massive results in the Lake Louise and Yoho regions with impressive propagation. Many large avalanches have run to the bottom of their run outs snapping trees and entraining moist snow at lower elevations.

Confidence

Due to the number and quality of field observations

Avalanche Problems

Deep Persistent Slabs

The entire snowpack is built upon a structurally weak base of facets. Large avalanches are reaching historical run outs and crossing valley bottom trails. Avoid exposure to overhead hazard and stick to moderate angled supported terrain.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 2 - 4

Wind Slabs

Wind slabs over 1m deep exist at higher elevations, and on ridges near tree line. This slab is still reactive in tests and can produce avalanches. Cornices have also grown significantly and are fragile. Avoid all areas with recent wind effect.

If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 2 - 3