Avalanche Forecast

Issued: Feb 7th, 2017 3:40PM

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

Avalanche Canada jsmith, Avalanche Canada

Touchy storm slabs reactive to human triggers. Storm slabs are most reactive in southeast portion of the region that received the highest snowfall amounts.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Wednesday: Mostly cloudy / Light, southerly winds/ Freezing level valley bottom.Wednesday night: 5-10 cm new snow / Moderate, southwesterly winds / Freezing level valley bottomThursday: 15-20 cm new snow / Strong, southwesterly winds / Freezing level 800m.Friday: Mostly cloudy with flurries / Moderate, southwesterly winds / Freezing level 1000 m.

Avalanche Summary

On Monday, numerous size 2.5 natural and explosive triggered storm slab avalanches were reported at Kootenay Pass. The avalanches were reported as having impressive propagation up to 150 m wide. North of Nelson, there was a widespread natural avalanche cycle to size 2. South of Nelson, there were several size 2.5 natural storm slab avalanches reported.

Snowpack Summary

45-85cm of recent storm snow has created touchy storm slabs at all elevations and aspects. Snowfall amounts have been highest around Kootenay Pass and taper dramatically as you go north. These slabs have been reported as being 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. 50-100 cm of snow now overlies the weak layer of surface hoar(feathery crystals) and facets(sugar snow) that was buried in mid-January. There has only been one recent report of an avalanche on this interface, but this may change with the increasing load. 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

An icon showing Storm Slabs
Storm slabs will be most reactive in wind effected terrain. Use caution as you transition into wind effected snow.
Use small slopes with low consequence to test the bond of the new snow.Watch for signs of instability such as whumpfing, shotting cracks, or recent natural avalanching.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
Smaller storm slabs may step-down to deeper weak layers, resulting in large, destructive avalanches.
Dig down to find and test weak layers before committing to a line.Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Feb 8th, 2017 2:00PM