Avalanche Forecast

Issued: Feb 10th, 2017 5:41PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. 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 storm snow.

Summary

Confidence

Moderate -

Weather Forecast

Seasonal temperatures and isolated flurries through the weekend. Significant warming Monday onwards. SATURDAY: 5-10cm possible by Saturday morning. Mostly cloudy with isolated flurries. / Light to moderate southwesterly winds/ Freezing level around 1000 m / Alpine highs to -7 Celsius SUNDAY: Cloudy with sunny breaks / Light, southwesterly winds / Freezing level around 700m. MONDAY: Mainly cloudy, warming significantly with highs to +1 Celsius / Light southwesterly winds / Freezing level rising to 1500 m in the afternoon.

Avalanche Summary

A widespread natural avalanche cycle (to Size 2.5) occurred on all aspects and elevations at treeline and above from Thursday into Friday.

Snowpack Summary

Another 20-30 cm of wet snow fell up to 1800m on Thursday and sits on top of the 45-85cm of recent storm snow: This has created touchy storm slabs at all elevations and aspects. Snowfall amounts have been highest around Kootenay Pass. These 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.Â 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

Thursday's storm started cold and ended warm. This creates a dangerous condition where warmer heavy snow is sitting on-top colder snow, making storm 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: All elevations.

Likelihood

Likely

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 11th, 2017 2:00PM