Avalanche Forecast

Issued: Feb 12th, 2018 5:33PM

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

cgarritty, Avalanche Canada

Kootenay Boundary.

Watch for new wind slabs distributed across a wide range of aspects and elevations. A cornice or wind slab release would be one of the most effective ways to trigger a deeply buried weak layer.

Summary

Confidence

High -

Weather Forecast

Tuesday: Cloudy with flurries beginning in the afternoon and bringing approximately 10 cm of new snow by Wednesday morning. Light to moderate northwest winds, strong in the alpine and increasing overnight. Alpine high temperatures to around -5 under a lingering temperature inversion. Cooling at lower elevations.Wednesday: Mainly cloudy with lingering isolated flurries and a trace to 5 cm of new snow. Light to moderate northwest winds. Alpine high temperatures around -9.Thursday: A mix of sun and cloud. Light to moderate southwest winds. Alpine high temperatures of -10.

Avalanche Summary

A widespread avalanche cycle occurred this week on all aspects and elevations. Persistent slabs up to size 3 were observed during the peak of the storm loading on Thursday. On Friday and Saturday, natural activity slowed down, but large explosive and machine-triggered avalanches continued to be reported.The natural cycle has wound down, but human-triggering remains a real concern. You might be surprised by how large an avalanche can be triggered and how far it could run.

Snowpack Summary

Storm snow accumulations from the past week vary from 10-45cm across the region at upper elevations. In the alpine this new snow has been redistributed to leeward slopes from strong northwest winds. Fragile cornices may be found at ridge top. Below 1850 m, around 5 cm of low density snow covers a hard crust. We now have 1- 2 m of settled snow sitting on three significant surface hoar/crust layers that were formed early to mid-January, and back in December. Near the base of the snowpack a crust/ facet interface exists that will likely haunt us all season. These persistent weak layers that lurk within the snowpack have produced large and destructive avalanches. Although this activity has been diminishing gradually, recent activity and continued sudden snowpack test results have kept them a top concern in the region.The complex and widespread nature of our multiple overlapping persistent slab problems continues to demand respect and diligence from backcountry travelers in the region.

Problems

Wind Slabs

Recent strong and variable winds have redistributed loose snow into new wind slabs and fragile cornice growth on a variety of aspects.

If triggered, wind slabs or cornices may step down to deeper layers and result in large avalanches.Watch for patterns of recent wind loading and avoid areas where the surface is stiff or slabby.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Persistent Slabs

Several deeply buried weak layers exist in the snowpack. Although the likelihood of triggering a persistent slab is gradually decreasing, the consequences remain very high.

Avoid lingering in runout zones.Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Feb 13th, 2018 2:00PM