Archived

Avalanche Forecast

Dec 20th, 2015–Dec 21st, 2015

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

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

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

1: Low

The avalanche danger rating at treeline will be low

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Regions: South Columbia.

Extensive wind effect has likely occurred at higher elevations. The best (and safest) riding may be found on sheltered slopes at treeline and below.

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

Light flurries (no more than 3 cm each day) are expected for all 3 days of the forecast period. Moderate southwest ridgetop winds forecast for Monday and Tuesday will ease to light and westerly by Wednesday. The freezing level should sit at valley bottom for the foreseeable future. For a more detailed weather discussion, please check-out our Mountain Weather Forecast at: avalanche.ca/weather.

Avalanche Summary

Recently, natural and human-triggered wind slab avalanches in the size 1-1.5 range were observed in the alpine and at treeline. As the stormy weather tapers-off, so should natural avalanche activity. However, wind slab avalanches may remain sensitive to human-triggering for a few days.

Snowpack Summary

On Sunday there was up to 15cm of fresh snow bringing the 48 hour total to about 35cm in the deeper snowpack parts of the region. Strong to extreme southerly winds have likely redistributed much of this snow into much deeper wind slabs in exposed lee features in the alpine and at treeline. In more sheltered terrain, I would expect deep powder and really good riding. Between 80 and 120cm below the surface you'll likely find a weak layer of well-developed surface hoar. This layer is most widespread and reactive at lower elevations (between 1400m and 1800m.) Snow pit tests suggest that human triggering of this interface has become unlikely in most areas. That said, if it does fail the overlying slab is stiff enough to propagate over a wide distance. Below this layer, the snowpack is thought to be generally strong and well-settled.

Avalanche Problems

Wind Slabs

Intense wind transport was observed on Sunday, and new wind slabs were reported to exist at treeline and in the alpine. I'd head for sheltered, lower elevation terrain where the riding is probably the best (and safest).

Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Be alert to conditions that change with elevation.>The best powder will be found in sheltered locations at or below treeline.>

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 3

Persistent Slabs

A layer of buried surface hoar can be found between 1400m and 1800m. Although this layer has become less likely to trigger, I'd remain cautious on steep roles in cut-blocks and open glades below treeline.

Conditions are greatly improved, but be mindful that deep instabilities are still present below treeline.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood: Unlikely - Possible

Expected Size: 2 - 4