Avalanche Forecast

Issued: Jan 7th, 2017 5:09PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Persistent Slabs.

Avalanche Canada cgarritty, Avalanche Canada

A bit of new snow combined with sustained winds will keep our wind slab problem alive and well. Even if the rating is still Moderate, stability will be decreasing as new snow accumulates.

Summary

Confidence

Moderate - Timing of incoming weather systems is uncertain on Sunday

Weather Forecast

Sunday: Cloudy with isolated flurries and a trace of new snow. Winds moderate from the south. Alpine temperatures around -9.Monday: Flurries bringing 5-15cm of new snow. Winds moderate gusting to strong from the southwest. Freezing level rising to 1000 metres and alpine temperatures around -5Tuesday: A mix of sun and cloud with isolated flurries and a trace of new snow. Winds light to moderate from the northwest. Freezing level back to valley bottom and alpine temperatures around -15, closer to -9 in the south of the region.

Avalanche Summary

A Size 2 natural cornice fall 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 other avalanche activity has been reported in the region, but wind slabs may remain reactive to human triggers in specific areas, such as the immediate lee of ridges.

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.

Problems

Wind Slabs

An icon showing Wind Slabs
Recent strong winds have created wind slabs on a wide range of aspects. Analyze each slope for patterns of wind loading and be especially cautious of thin trigger points. A small wind slab avalanche can trigger deeper weaknesses.
Avoid travelling in areas that have been reverse loaded by winds.Use ridges or ribs to avoid pockets of wind loaded snow.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
The surface hoar and facets buried mid-December formed a weak layer that remains a concern in shallow snowpack areas. Dig down and test this layer if you're considering a steeper line at treeline or higher.
Avoid convexities or areas with a thin or variable snowpack.Dig down to find and test weak layers before committing to a line.Be aware of the potential for large avalanches due to the presence of buried weak layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Valid until: Jan 8th, 2017 2:00PM

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