Avalanche Forecast

Issued: Mar 5th, 2018 5:37PM

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

shorton, Avalanche Canada

Kootenay Boundary.

Buried weak layers sit beneath the new snow and have shown signs of being reactive to human triggers. Approach steep and convex terrain very cautiously.

Summary

Confidence

High -

Weather Forecast

TUESDAY: Mostly cloudy with some sunny breaks in the afternoon, light west wind, freezing level rising to around 1000 m.WEDNESDAY: Sunny, moderate southwest wind, freezing level rising to around 1300 m.THURSDAY: Increasing cloud and light flurries starting in the afternoon, moderate southwest wind, freezing level rising to around 1300 m.

Avalanche Summary

On Sunday, a skier triggered a large avalanche on a north treeline slope in the Rossland area that failed on a surface hoar layer 80 cm below the surface. Skiers in the Rossland area also experience whumpfing and ski cut a size 1 wind slab on a east aspect at 1700 m. Elsewhere in the region, a natural wind slab was observed on a northwest aspect at 2150 m and explosive control produced numerous size 2 storm slabs on south aspects.On Saturday, explosive control produced several size 1-2 storm slabs in the top 15-30 cm of snow.

Snowpack Summary

Isolated flurries have delivered sporadic and localized accumulations of new snow. Snowfall amounts from the past week are 40-60 cm with the exception of the Rossland area which received 80-100 cm.A mix of interfaces 50-100 cm below the surface will potentially remain reactive to human triggering and have given sudden results in recent snowpack tests. This includes small surface hoar on polar aspects and a sun crust on solar aspects.Two deeper weak layers that formed in January and December are gradually gaining strength. Several surface hoar and facet layers are buried 1 to 2 m below the surface and there is a crust/ facet interface near the base of the snowpack. No avalanches have been reported on these layers for a few weeks and they are thought to have gone dormant at this time.

Problems

Persistent Slabs

A few weak layers exist 50-100 cm below the surface and include sun crusts on south-facing terrain and surface hoar on north-facing terrain. They have been reactive to skiers and produced some concerning results in snowpack tests.

Be cautious on convex rolls at and below treeline where buried surface hoar may be preserved.Choose well supported terrain without convexities.Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 2.5

Storm Slabs

Storm snow from the past week may still be reactive to human triggers, especially in areas like the Rossland area that received up to 80 cm of snow. Triggering is most likely near ridge crests and around mid-slope features like convexities.

Be alert to conditions that change with elevation.Approach steep lee and cross-loaded slopes with caution.Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Mar 6th, 2018 2:00PM