Archived

Avalanche Forecast

Jan 9th, 2017–Jan 10th, 2017

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

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

2: Moderate

The avalanche danger rating below treeline will be moderate

Regions: Northwest Inland.

Weak, sugary snow at the bottom of the snowpack remains a primary concern. This is especially true in large, steep, and rocky alpine features with variable snowpack depths.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Tuesday: Clear skies / Moderate to strong northerly winds / Alpine temperatures of -15Wednesday: Clear skies / Moderate northerly winds / Alpine temperatures of -5Thursday: Light flurries / Extreme westerly winds / Alpine temperatures of -12

Avalanche Summary

A large natural slab avalanche was reported from the Babine Range on Sunday. The slab, which ran approximately 200m, was reported to be 50m wide and 50cm deep. The weak layer associated with this avalanche is unknown. Thanks to the individual who submitted the observation via the Mountain Information Network.

Snowpack Summary

10-20 cm of new snow fell last weekend. Observations have been limited, although I suspect these accumulations have likely been shifted into wind slabs at treeline and in alpine. Snow depth at treeline varies from about 1 m in most areas to 2 m in deeper snowpack areas in the south and west of the region, and up to 250 cm in the alpine. The shallow snowpack areas mostly consist of weak facetted or sugary grains beneath hard slabs. These hard slabs may produce surprisingly long fractures resulting in large avalanches, and in some instances they may step down to weak snow crystals near or at the ground. In addition to the facets, a thick layer of buried surface hoar may be found 30-40 cm below the surface. There is another persistent weakness that formed during the early December cold snap which is now about 50-70 cm deep. A crust from mid-November may be lurking close to the ground nestled in amongst the facets.

Avalanche Problems

Deep Persistent Slabs

In most areas this is a lower probability, high consequence scenario and requires a conservative approach to larger terrain features. Avoid likely trigger spots such as steep and rocky areas with a shallow snowpack.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2 - 3

Wind Slabs

Forecast strong to extreme winds may redistribute any remaining loose surface snow into fresh wind slabs, adding to an ongoing wind slab problem. Wind slabs may step down to deeper weak layers resulting in surprisingly large avalanches.

Use ridges or ribs to avoid pockets of wind loaded snow.Be cautious as you transition into wind affected terrain.Avoid areas where the snow feels stiff or slabby.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2