Avalanche Forecast

Issued: Jan 10th, 2018 5:34PM

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

cgarritty, Avalanche Canada

North Columbia.

Avalanche activity has been at a steady peak and touchy conditions will persist. Travel in avalanche terrain is not recommended.

Summary

Confidence

High -

Weather Forecast

Thursday: Mainly cloudy with isolated flurries and a trace of new snow. Light southeast winds. Alpine high temperatures to -11.Friday: A mix of sun and cloud. Light southwest winds. Alpine high temperatures to -9.Saturday: Mainly cloudy with isolated flurries and a trace of new snow.. Light to moderate west winds. Alpine high temperatures to -2.

Avalanche Summary

Reports from Tuesday suggest a high point in a natural avalanche cycle on both the January 5 surface hoar layer as well as the December 15 surface hoar layer. Avalanche activity on these interfaces was extensive, with natural and remote (from a distance) triggers forming a large percentage of observations. Sizes ranged from Size 1-3, with slab depths ranging from 30-80 cm, and activity was observed on all aspects and elevation ranges. Reports from the previous two days showed similar activity.Looking forward, incremental loading from new snow on Thursday is likely to keep the region in an active pattern of avalanche activity that may intensify toward the weekend with forecast clearing and warming.Please share your recent observations through the Mountain Information Network (MIN).

Snowpack Summary

Recent storms have brought 40-60 cm of new snow to the region. The new snow sits on surface hoar on sheltered slopes as well as sun crust on steep solar aspects. Numerous storm slab avalanches resulted as the new snow formed a slab before bonding to the surface. Moderate to strong southwest winds accompanied the snowfall at higher elevations, creating wind slabs in lee features.As the new snow continues to consolidate, it is forming a dangerous slab above several persistent weak layers that exist in the snowpack. The first of these is the surface hoar that exists at the new snow interface. Recent snowpack tests and avalanche activity show a high degree of reactivity at this layer. Below it, the December 15 surface hoar is now buried 50 to 100 cm deep. This layer has been the failure plane in many recent destructive slab avalanches. Its reactivity has been most apparent at treeline and below treeline. Deeper in the snowpack at depths of about 90 to 150 cm, a rain crust from November is producing variable snowpack test results, from sudden fractures to no result. This layer is considered dormant but could be triggered in thin spots around variable snowpack areas in the alpine.

Problems

Storm Slabs

Many avalanches have been human-triggered in the recent 30 to 60 cm of storm snow. The snow is sitting on variable surfaces and it is not bonding well to them. Storm slabs likely to be especially reactive where they have been affected by the wind.

If triggered, the storm slabs may step down to deeper layers and result in large avalanches.The new snow sits on a persistent weak layer and will require more time than usual to stabilize.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Persistent Slabs

Light triggers have released large avalanches on this layer, which is buried around 50 to 80 cm in the snowpack. Shallower storm slabs could step down to this layer. When triggered, this layer is producing large, destructive avalanches that run far.

Be aware of the potential for large avalanches due to the presence of buried surface hoar.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 3

Valid until: Jan 11th, 2018 2:00PM