Avalanche Forecast

Issued: Jan 14th, 2015 8:25AM

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

pgoddard, Avalanche Canada

Kootenay Boundary.

A problematic weakness in the snowpack still has local professionals on edge. The weight of a person could trigger a destructive avalanche. If you are unsure, stick to conservative terrain.

Summary

Confidence

Fair

Weather Forecast

Light amounts of precipitation are expected on Thursday night/ Friday. SW winds strengthen on Thursday, then switch to W-NW and ease on Friday. The freezing level hovers around 700m.

Avalanche Summary

Two large slabs were observed in the Nelson backcountry, which are suspected to have failed naturally in response to wind-loading over the last 1-3 days. One was a size 2.5 slab on a NW aspect at 2300m, while the other was a size 3 on an E aspect. The crowns were 120-150 cm deep. On Saturday, skiers triggered numerous persistent slab avalanches to size 2 in the north of the region, in some cases remotely from a distance of 10m. On Sunday, a couple of persistent slab avalanches in the size 2.5 range were triggered between 2100 and 2300m from a distance of up to 100m. Avalanche activity has slowed, but there is still the potential for human-triggering of large avalanches.

Snowpack Summary

Large surface hoar crystals are growing on the snow surface. New snow or new wind slabs are likely to bond poorly to this surface. Underneath this a thin frozen crust exists up to about 1900m. Our main concern continues to be a crust/surface hoar combo buried in mid-December. This touchy layer is 60-120cm down and has the potential to be triggered by people and produce surprisingly large avalanches. Operators are still tip-toeing around and treating this interface with suspicion. A facet/crust layer near the base of the snowpack has mostly been dormant, apart from recent activity in the Bonnington Range which suggests it may still be reactive in isolated terrain.

Problems

Persistent Slabs

Persistent slabs may be triggered by the weight of a person or snowmobile in specific areas. Most likely trigger points are where the snowpack transitions from thick to thin, around rocks and trees, and on steep convex rolls.

Avoid convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 6

Wind Slabs

Wind slabs may be found on a variety of slopes due to changes in wind direction. A wind slab could trigger a deeper weak layer, creating a surprisingly large avalanche.

Be cautious as you transition into wind affected terrain.>Travel on ridgetops to avoid wind slabs on slopes below.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Jan 15th, 2015 2:00PM