Avalanche Forecast
Regions: Banff Yoho Kootenay.
Avalanche Control is planned for Highway 93South and the Trans Canada Highway Monday (click links for more info) Be aware of reactive new storm and windslabs as well as the potential for avalanches on the deep persistent layer to reach run outs.
Weather Forecast
Another cold front reaches the forecast area early Sunday eventing: winds will spike again, and temperatures are forecast to drop still further to -18C in the alpine. An additional 10cm can be expected overnight before a break early Monday morning. Another warm front will approach late Monday with rising temps and increased likelihood of snow.
Snowpack Summary
20-40 cm of storm snow, strong Westerly winds and mild temperatures is promoting storm and wind slab formation. At tree line, new snow sits on pockets of surface hoar in sheltered areas and sun crust on steep solar aspects. Generally, the upper snowpack of denser snow sits over a weaker lower snowpack consisting of facets, depth hoar and crusts.
Avalanche Summary
A decrease in natural activity today following a spike yesterday with strong winds. A size 3 on Mt. Field, a size 2.5 on Vermillion Peak, and another size 2.5 slide in the Sunshine area were directly observed Saturday. SSV avalanche control crews reported touchy and widespread wind slabs today particulary in N and E facing alpine terrain.
Confidence
Intensity of incoming weather systems is uncertain on Monday
Avalanche Problems
Storm Slabs
20-40cm of storm snow has been accompanied by strong SW winds. Thick slabs in the lee of alpine and treeline features can be expected. Be on the look out in sheltered areas TL and below as this snow may be settling into a slab over surface hoar.
- If triggered the storm slabs may step down to deeper layers resulting in large avalanches.
- Use caution in lee areas. Recent wind loading has created wind slabs.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 1 - 2.5
Deep Persistent Slabs
We have seen a few examples of these slabs becoming reactive during the storm. These large avalanches reach run out zones. As loading continues over the next few days, avoid exposure to overhead avalanche terrain.
- Avoid shallow snowpack areas where triggering is more likely.
- Be aware of the potential for wide propagations which could result in large avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 2 - 3.5
Loose Dry
While winds stay elevated and precipitation continues to come in, loose dry avalanches will be a problem in steep terrain. These small events can be enough to trigger a slab on slopes beneath cliffs or on ledges in gully features.
- Be very cautious with gully features.
- Use caution above ledges and cliffs where small avalanches may have severe consequences.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 1.5