Avalanche Forecast

Issued: Jan 9th, 2018 5:19PM

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.

cgarritty, Avalanche Canada

South Columbia.

"Touchy", "electric", "spicy"... A few of the words that have been used to describe recent conditions. Avalanche activity has been extensive and is set to persist over the coming days. Choose low angle, low consequence terrain.

Summary

Confidence

Moderate -

Weather Forecast

Wednesday: Mainly cloudy with scattered flurries and 3-5 cm of new snow. Light southwest winds. Alpine high temperatures to around -7.Thursday: Cloudy with flurries bringing 5-10 cm of new snow. Light south winds. Alpine high temperatures to about -5.Friday: A mix of sun and cloud. Light southwest winds. Freezing level rising to 1300 metres and alpine high temperatures to about -2.

Avalanche Summary

Preliminary reports from Tuesday describe 'electric' conditions in several areas in the South Columbias, where extensive storm slab reactivity was observed. It is as yet uncertain to what degree deeper persistent slab problems were active.Reports from Monday showed a continuation of recent heightened avalanche activity, with numerous storm slabs and persistent slabs releasing from Size 1 to 2.5 both naturally and with human triggers. Activity was observed on all aspects and elevations and slab depths have ranged from about 20-80 cm. This has been a consistent and increasing trend, with around 5-10 avalanches being reported each day for the past week on either the January 5 surface hoar or the much deeper December 15 surface hoar.Please share your observations through the Mountain Information Network.

Snowpack Summary

30-60 cm of new snow has accumulated on surface hoar in sheltered slopes and a sun crust on steep solar aspects. Numerous storm slab avalanches resulted as the new snow consolidated into a slab before bonding to the underlying surface. Strong southwest winds have accelerated slab formation at higher elevations.The additional snow has also increased the reactivity of a number of buried weak layers. 50-100 cm of snow now overlies a layer of weak and feathery surface hoar, found primarily at and below treeline. Dubbed the December 15 surface hoar, this layer has been the failure plane in many recent destructive slab avalanches. See the Avalanche Summary for recent activity. Deeper in the snowpack (90 to 150 cm), a crust that formed back in November is producing variable test results (sudden to no result). This layer is considered dormant but could be triggered in thin spots around variable-depth 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. The new snow is likely to be especially reactive where it has been affected by the wind.

Use extra caution in wind affected areas. Recent wind loading has created wind slabs.If triggered, the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Persistent Slabs

Skier traffic has triggered large avalanches on this layer, which is buried around 40 to 80 cm in the snowpack. Shallower storm slabs could step down to this layer. If triggered, this layer could produce large, destructive avalanches that run far.

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 10th, 2018 2:00PM