Avalanche Forecast

Issued: Feb 12th, 2017 5:55PM

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

mgrist, Avalanche Canada

Kootenay Boundary.

Touchy storm slabs are reactive to human triggers. Use small slopes with low consequence to test the bond of the most recent snow.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Sunny and warm by Tuesday afternoon... and then some wet snow on Wednesday / Thursday. MONDAY: Sunny, warming significantly with alpine highs to +3 Celsius / Moderate southeasterly winds / Freezing level around 1800 m TUESDAY: Sunny with cloud developing in the afternoon / High temperatures to +5 Celsius / Light, southwesterly winds/ Freezing level around 2800 m. WEDNESDAY: Cloudy with some wet snow at higher elevations / Moderate southerly winds / Freezing level around 2500m.

Avalanche Summary

No new observed. See Whitewater Ski Patrol's great video (here) posted on the Backcountry Skiing Canada web site for a concise summary of details to Feb 9th, and some excellent video footage of a Size 2.5 avalanche running on the Goat Slide path near Whitewater (with crown height to 2.5m).

Snowpack Summary

At the end of last week up to 30cm additional snow fell (mostly near Nelson) and brought the recent storm snow total to 65-100cm, creating touchy storm slabs at all upper elevations and aspects. Snowfall amounts have been highest around Kootenay Pass. Slabs have been reported as very reactive to human triggers and are sitting on a variety of surfaces; including scoured surfaces in wind exposed terrain, surface hoar (size 2-3 mm) in sheltered locations, and sun crust on steep solar aspects. Snowpack tests near the Valhallas have given moderate, propagation-likely results down 50-70cms on the Feb 3rd interface. Areas with a shallower snowpack (less than 150 cm) have a generally weak snowpack structure with sugary facets near the ground. This includes shallow alpine slopes and most of the Rossland range. It is possible for storm slab avalanches to step-down to these deeper weak layers, resulting in large, destructive avalanches.

Problems

Storm Slabs

The last storm started cold and ended warm, creating a dangerous condition where warmer heavy snow is sitting on-top colder snow. Wind effect also made slab avalanches much more likely.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Use small slopes with low consequence to test the bond of the storm snow.Watch for signs of instability such as whumpfing, shotting cracks, or recent natural avalanching.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

Storm slabs may step-down to deeper weak layers, resulting in large, destructive avalanches.

Wait to see how the snowpack responds to increased loads before venturing out into bigger terrainAvoid likely trigger spots such as steep and rocky areas with a shallow snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Feb 13th, 2017 2:00PM