Archived

Avalanche Forecast

Jan 8th, 2017–Jan 9th, 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

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

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: Purcells.

A complex set of avalanche problems is affecting the region. Old and new wind slabs on a variety of aspects as well as persistent slabs all demand your careful evaluation.

Confidence

Moderate - Forecast snowfall amounts are uncertain on Monday

Weather Forecast

Sunday night: Flurries delivering 5-10 cm of new snow with moderate southwest winds.Monday: Flurries bringing another 5-10 cm of new snow. Winds moderate gusting to strong from the west. Freezing level to 1000 metres with alpine temperatures around -7.Tuesday: A mix of sun and cloud with isolated flurries bringing up to 5 cm of new snow. Winds light to moderate from the northwest. Freezing level returning to valley bottom and alpine temperatures around -14.Wednesday: A mix of sun and cloud with no new snow. Winds light from the northwest. Alpine temperatures around -17.

Avalanche Summary

Recent reports include a Size 2 natural cornice fall that was observed on Friday in the Bugaboos area. The cornice released from a northeast-facing feature in the alpine and its failure to trigger any slab below might be attributed to recent scouring of snow from that aspect. No new avalanche activity was reported on Saturday, but new snow over Sunday and Monday is expected to form touchy slabs in lee terrain.

Snowpack Summary

A trace of new snow has covered a layer of surface hoar that was growing on the surface before January 6. Below the surface, recent cold temperatures have been promoting faceting of the upper snowpack. In exposed areas at all elevations, recent winds have scoured windward slopes and formed hard wind slabs in unusual places as the winds shifted from west to northeast. Continued moderate variable winds have been keeping wind slabs fresh and touchy in some areas. The layer of facets and surface hoar that was buried mid-December has been giving hard and broken results or non-results in snowpack tests where it is found around a metre below the surface. Snowpack tests in shallower areas, however, have yielded moderate sudden planar results on this persistent weakness, suggesting the primary concern for persistent slab avalanches is in shallow snowpack areas. With that said, the potential for a wind slab avalanche to step down to this weak layer remains a concern where it lies deeper in the snowpack. The lower snowpack is well bonded and features a thick rain crust near the ground.

Avalanche Problems

Wind Slabs

New snow and wind over Sunday and Monday will build fresh wind slabs in lee terrain, but pre-existing wind slabs can already be found on a wide range of aspects. Be sure to consider both current and previous wind loading patterns as you travel.

Be cautious as you transition into wind affected terrain.Use ridges or ribs to avoid pockets of wind loaded snow.Be alert to conditions that change with aspect and elevation.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2

Persistent Slabs

The surface hoar and facets buried mid-December formed a weak layer that remains a concern in shallow snowpack areas. Remember that a smaller wind slab avalanche may provide enough of a trigger to 'step down' to this deeper weakness.

Be aware of the potential for large avalanches due to the presence of buried weak layers.Dig down to find and test weak layers before committing to a line.Avoid convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Unlikely - Possible

Expected Size: 1 - 3