Avalanche Forecast

Issued: Jan 8th, 2018 5:03PM

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

mconlan, Avalanche Canada

Cariboos.

New snow is falling on numerous weak layers and will likely be reactive to natural and human triggers. Storm slabs have the potential to step down and trigger deeper persistent weak layers. Conservative terrain choices are recommended.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

TUESDAY: Cloudy with light flurries, accumulation 5-10 cm, light to moderate westerly winds, alpine temperature dropping to -10 C over the day, freezing level below valley bottom.WEDNESDAY: Partly cloudy with intermittent flurries, light to moderate southwesterly winds, alpine temperature near -14 C, freezing level below valley bottom.THURSDAY: Partly cloudy with intermittent flurries, light westerly winds, alpine temperature near -10 C, freezing level below valley bottom.

Avalanche Summary

Storm slab avalanches were reported on Saturday, being triggered naturally and by skier activity. The slabs were small to large (size 1 to 2) and generally observed around treeline and alpine terrain with depths of about 20 cm. One release occurred in a loaded lee slope near ridgetop.Please share your observations through the Mountain Information Network.

Snowpack Summary

20-40 cm of new snow fell on surface hoar in sheltered slopes and a sun crust on steep solar aspects and may not bond well to them. The snow also fell with moderate southwesterly winds in the alpine, which likely produced small wind slabs in lee features.The new snow could create a dangerous slab above buried weak layers. Numerous persistent weak layers exist deeper in the snowpack. Dry snow overlies three layers composed of weak and feathery surface hoar, with the deepest layer (December 15) buried 40 to 70 cm. This layer is shallower in the north of the region and deeper in the south of the region. The weak layer is found most often at treeline and below treeline. As the snow above the weak layers becomes more cohesive and forms a slab, the setup has the potential to create easily-triggerable destructive slab avalanches. Snowpack test results in this MIN post show that this layer could be reactive.Deeper in the snowpack at depths of about 70 to 100 cm, a rain crust from November is producing variable snowpack test results, from sudden fracture characters to no result. This layer is considered dormant but could be triggered where the snowpack is thin.

Problems

Storm Slabs

Around 20 to 40 cm of new snow, with the highest amounts in the south of the region, is sitting on variable surfaces and may not bond well to them. The snow could be deeper in northwesterly lee features due to strong winds.

If triggered, the storm slabs may step down to deeper layers resulting in large avalanches.Avoid exposure to terrain traps where the consequence of a small avalanche could be serious.Use caution when entering lee areas. Recent wind loading may have created wind slabs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

Around 40 to 70 cm of snow sits above a touchy weak layer. As this snow continues to settle and gains slab properties, a dangerous slab that is easily triggered may form. Shallower storm slabs could step down to this layer.

Use conservative route selection. Choose moderate-angled and well-supported terrain.Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Jan 9th, 2018 2:00PM