Avalanche Forecast

Issued: Dec 30th, 2016 5:33PM

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

shorton, Avalanche Canada

Cariboos.

Slab avalanches in steep terrain are still likely following the recent large storm, especially in wind-affected terrain. Conservative terrain choices are recommended.

Summary

Confidence

Moderate - Due to the number and quality of field observations

Weather Forecast

SATURDAY: Flurries with accumulations of 5 cm, moderate north winds, alpine temperatures around -12.SUNDAY: A mix of sun and cloud, moderate northeast winds, alpine temperatures around -18.MONDAY: A mix of sun and cloud, light northeast winds, alpine temperatures around -20.

Avalanche Summary

On Friday, avalanche reports were limited to a single size 4 natural avalanche, with no details about the sliding layer. I suspect smaller (size 2) avalanches were relatively widespread during the storm on Thursday and into Friday morning.Expect storm slab activity to continue into the weekend and be extra touchy in wind affected terrain. Triggering persistent slab avalanches also remains possible in thin snowpack areas.

Snowpack Summary

Between 30 and 60 cm of new low density snow has fallen over the past week. In higher elevation terrain, moderate to strong winds have promoted slab formation on lee and cross-loaded features. In sheltered areas and lower elevations, the low density snow has only just begun to show signs of consolidation into soft slab. A mid-December interface can be found buried 65-100 cm deep and consists of faceted (sugary) crystals and/or surface hoar. Recent tests suggest the the new snow is generally well bonded to this interface in most areas, but since the layer has still been reactive in some snowpack tests it should be investigated before pushing into steeper terrain. The lower snowpack is well consolidated and features a thick rain crust near the ground.

Problems

Storm Slabs

Avalanche danger will increase as low-density storm snow settles into a slab. Watch for signs like cracks in the snow to tell you this is taking place and expect slab formation to be a step ahead of you in wind exposed areas.

Be cautious as you transition into wind affected terrain.Avoids areas where the surface snow feels stiff or slabby.Be alert to conditions that change with elevation.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

A mid-December weak layer has generated some isolated reports of large avalanches in the Columbia Mountains to the south. This layer exists in the Cariboos as well, and may be easier to trigger in thin snowpack areas on the eastern edge of the range.

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 persistent weak layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Dec 31st, 2016 2:00PM