Avalanche Forecast

Issued: Feb 11th, 2018 5:06PM

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

pgoddard, Avalanche Canada

Kootenay Boundary.

A Special Public Avalanche Warning is in effect. Copy this link to view details: http://bit.ly/2nSOUyX

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Tuesday

Weather Forecast

MONDAY: Mainly sunny, with increasing clouds late in the day. Light winds. Treeline temperature near -10.TUESDAY: 5-10 cm snow. Light to moderate westerly winds. Treeline temperature near -5.WEDNESDAY: Flurries. Light winds. Treeline temperature near -8.More details can be found in the Mountain Weather Forecast.

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. This now brings 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 are reactive, producing large and destructive avalanches. The snowpack is extremely complex and requires respect and diligence at this time.

Problems

Persistent Slabs

Several troublesome layers exist in the snowpack. Although the likelihood of triggering a persistent slab has gone down, the consequences remain very high.

Avoid steep convexities or areas with a thin or variable snowpack.Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.Avoid lingering in runout zones.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 4

Wind Slabs

Recent north-westerly winds have left behind wind slabs and cornices on lee slopes.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Use conservative route selection. Choose moderate angled and supported terrain with low consequence.Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2.5

Valid until: Feb 12th, 2018 2:00PM