Avalanche Forecast
Regions: Banff Yoho Kootenay.
The avalanche hazard will gradually increase over the next two days as a warm storm arrives with a lot of wind. Watch for increased wind loading in overhead start zones and pull back into more conservative terrain as the snow arrives.
Weather Forecast
5 cm of new snow is expected on Tuesday during the day with another 10-20 cm Tuesday night into Wednesday morning. Alpine winds will remain in the Strong to Extreme range out of the SW throughout the storm. Temperatures are looking fairly warm. -4 to -2 C at treeline and around -6 C in the alpine which could result in rapid slab development.Â
Snowpack Summary
A couple cm's of new snow mixed with facets and surface hoar on the surface. Thin suncrust on some steep solar aspects. Wind effect in alpine areas. Three persistent weak layers from Dec are down 30-100 cm. These have generally been unreactive but occasionally result in hard sudden planar shears. The Nov. 5 basal crust/facets are currently dormant.
Avalanche Summary
Little avalanche activity Monday. A powder cloud was observed on the East face of Mt Temple that may have been triggered by the wind. One cornice triggered size 2 slab avalanche was observed in the alpine on Mt Field from the last 48 hours. A skier triggered size 0.5 slab in a very steep open glade just below treeline on Mt Field was also observed.
Confidence
Forecast snowfall amounts are uncertain on Wednesday
Avalanche Problems
Wind Slabs
As the storm arrives Tuesday we expect new wind slabs to form in the alpine. On Tuesday these will likely remain small and somewhat difficult to trigger but as more snow arrives this problem will increase in size and become easier to trigger.
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
- Minimize exposure during periods of loading from new snow and wind.
Aspects: All aspects.
Elevations: Alpine.
Likelihood: Possible
Expected Size: 1 - 2
Persistent Slabs
Three persistent weak layers from Dec exist in the top 100 cm of the snowpack. These have been mostly unreactive to skiers, but can produce hard sudden planar results in snow tests and have resulted in a couple skier triggered slabs in the last week.
- Dig down to find and test weak layers before committing to a piece of terrain.
- Convex features and steep unsupported slopes will be most prone to triggering.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood: Unlikely
Expected Size: 1 - 2