Archived

Avalanche Forecast

Jan 11th, 2015–Jan 12th, 2015

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: Kootenay Boundary.

Check out this great video blog post which describes conditions in the Nelson area: http://backcountryskiingcanada.com/forums/view/safety-talk/avalanche-conditions-report-video-1

Confidence

Good

Weather Forecast

A dry ridge of high pressure will dominate the region for the period. Valley cloud should develop for most days, although generally clear skies are expected at higher elevations. Winds are forecast to remain light from the northwest, while freezing levels should hover at (or near) valley bottom.

Avalanche Summary

On Saturday, skiers triggered numerous persistent slab avalanches to size 2 in the north of the region, in some cases remotely from a distance of 10m. With the stable weather pattern, recent storm instabilities should become much less reactive; however, I would expect ongoing skier-triggered avalanche activity on the December persistent weak layers.

Snowpack Summary

A dusting of low-density snow overlies well-developed surface hoar which sits above a melt-freeze crust. The crust is reported to exist on all aspects below about 1900m, and on steep solar aspects at higher elevations. Stubborn wind slabs are likely in exposed alpine and treeline terrain. The main snowpack concern is a buried surface hoar layer (down 60-120 cm), which is sitting on a hard rain crust in some places. This widespread persistent weakness, which formed in December, exists at all elevation bands and remains a concern for triggering.

Avalanche Problems

Persistent Slabs

Continued skier-triggered avalanche activity is a clear indication that weak layers, buried up to 120cm below the surface, have not gone away. I'd remain conservative in my terrain selection, and exercise cautious group management.

Choose conservative lines and watch for clues of instability.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 2 - 4

Wind Slabs

Storm accumulations from last week have likely gained considerable strength. That said, lingering wind slabs may still exist in the lee of ridge crests and terrain breaks.

Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 1 - 3