Avalanche Forecast

Issued: Jan 1st, 2017 4:34PM

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

shorton, Avalanche Canada

Purcells.

Watch for wind slabs in unusual places as we head into a clear cold week. Be extra cautious in thin snowpack areas where it may be possible to trigger deeper weak layers.

Summary

Confidence

Moderate - Wind speed and direction is uncertain

Weather Forecast

MONDAY: Mix of sun and cloud, light east winds, alpine temperatures around -20.TUESDAY: Sunny, light northeast winds, alpine temperatures around -18.WEDNESDAY: Mix of sun and cloud, 20-40 km/h north winds, alpine temperatures around -16.

Avalanche Summary

On Saturday, explosive avalanche control produced several size 1-2 slab avalanches on wind loaded features and some larger natural avalanches were observed on steep south facing slopes. MIN reports from the past few days suggest the recent snow is still reactive to rider triggers, including a report from the Kicking Horse area of a skier caught in a small slide on a southwest aspect and another report from from west of Kimberly where a ski cut in a cutblock resulted in a size 2 persistent slab avalanche.Looking ahead to Monday, expect wind slabs to remain reactive to human triggers. The additional load may also make the persistent slab over the mid-December interface more reactive in thin snowpack areas.

Snowpack Summary

The region received 40-60 cm of new snow between Christmas and New Years. This snow has been redistributed by strong winds that have come from a variety of directions and loaded leeward and cross-loaded features. Sunny skies will promote settlement of the snow on open south-facing slopes. The mid-December facet/surface hoar interface can be found buried 40-80 cm deep. This layer has shown signs of being poorly bonded to the overlying slab in snowpack tests, and has produced intermittent avalanche activity in shallow snowpack areas. The lower snowpack is well bonded and features a thick rain crust near the ground that appears to be dormant.

Problems

Wind Slabs

With recent winds coming from a variety of directions watch for signs of stiff or slabby snow on less commonly loaded slopes. Denser slabs found on south aspect slopes could be made more unstable by the sun.

Use ridges or ribs to avoid pockets of wind loaded snow.Avoid travelling in areas that have been reverse loaded by winds.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

40-80 cm of snow sits above a weak layer of facets from mid-December and has recently been reactive in parts of the region with thin snowpacks. Winds slabs may also step down and trigger this layer.

Dig down to find and test weak layers before committing to a line.Avoid lingering in runout zones.Be aware of the potential for large avalanches due to the presence of buried weak layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Jan 2nd, 2017 2:00PM