Avalanche Forecast
Regions: Banff Yoho Kootenay.
Strong to Extreme winds and more snow will continue to develop new wind slab at upper elevations. This new load overlays a weak faceted snowpack in many areas.
Weather Forecast
Strong to extreme Westerly winds at mountain top will begin to dissipated late Tuesday. A short pulse of precipitation is forecasted late Monday, with accumulation amounts of 5-20cm of snow. Freezing levels with remain at valley bottom with temperatures ranging from -5 to -10.
Snowpack Summary
15 to 30cm of storm snow since Friday. Snow and wind have created wind slabs in alpine lee areas and exposed tree line slopes. In thin snowpack areas 30-60 cm of snow sits over weak facet interfaces and facet sun crust interfaces on southerly aspects. In deeper snowpack areas there was less facetting, and the recent storm snow is bonding better.
Avalanche Summary
Saturday we received a report of a skier accidental size 2.5 that released out of a southerly aspects at tree line on Simpson Ridge. A fracture line profile today revealed that this avalanche failed on a weak facet interface 40-80cm down. Other reports and observations have indicated an increase in avalanche activity on this persistent weak layer.
Confidence
Avalanche Problems
Wind Slabs
Strong to extreme Westerly winds continue to create wind slabs in the alpine and exposed tree line lee areas. Places where wind slabs sit over a weak facet interface are still a concern. Dig down to confirm this.
- Use caution in lee areas. Recent wind loading has created slabs over weaker snow.
- Watch for shooting cracks or stiffer feeling snow. Avoid areas that appear wind loaded.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 2.5
Loose Dry
Incremental imputes of new snow and increased wind will add to the problem. Watch your exposure to steep terrain traps and gully features.
- On steep slopes, pull over periodically or cut into a new line to manage sluffing.
- Be cautious of sluffing in steep terrain, particularly where the debris flows into terrain traps.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 2
Persistent Slabs
Two weak facet interfaces exist in the top meter of the snowpack. On south aspects this problem could be associated with a sun crust. These layers are present in many areas, but we have uncertainty on where they will be reactive.
- Dig down to find and test weak layers before committing to a line.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Unlikely - Possible
Expected Size: 1.5 - 3