Archived

Avalanche Forecast

Feb 6th, 2020–Feb 7th, 2020

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

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

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: Banff Yoho Kootenay.

If committing to larger lines, understand you may be rolling the dice, the deeper weak layers are still being triggered by a skiers weight and producing large avalanches.

Size 2.5 Skier Accidental

Weather Forecast

Mix of sun and cloud with isolated flurries for the region on Friday. Temperature range of -3 to -12 with moderate SouthWest winds. 5-10cm of snow forecasted for Friday night into Saturday.

Snowpack Summary

Up to10cm of snow overnight brings the weekly total to 40-80cm. A rain crust up to1900m is now buried by 10-20cm of snow. Wind slabs exist in the alpine and at tree line. The Dec 31 layer of facets, surface hoar and sun crust is down 50-100cm. The deep persistent basal layer is ~30cm above the ground and is more developed in shallow snowpack areas.

Avalanche Summary

Skier triggered sz 2.5 in the Lipalian 3 in the Lake Louise backcountry, no injuries.

Explosive work at local ski areas has seen the deep persistent layer fail, up to sz 2, to ground under light loads (1kg explosive = human load).

Last weekends natural avalanche cycle saw large avalanches up to size 3.5 running to valley bottoms.

Confidence

Avalanche Problems

Wind Slabs

Recent moderate-strong winds have built wind slabs in the alpine down to tree line. These wind slabs could be quite thick in some spots and should be treated with caution, especially in alpine features.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2

Deep Persistent Slabs

Deep releases on the facets and depth hoar could be less likely but are hard to predict. Dealing with the uncertainty around this layer can be somewhat managed by avoiding large, committing terrain and areas with a thin snowpack.

Avoid shallow snowpack areas where triggering is more likely.
Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 2 - 3.5

Persistent Slabs

This layer of surface hoar, facets and crusts is down 50 to 100cm and produces variable results, many in the hard range or no result.

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

Aspects: All aspects.

Elevations: Treeline.

Likelihood: Possible

Expected Size: 1.5 - 3