Avalanche Forecast
Issued: Jan 11th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
kdevine,
Avalanche Canada
Fresh snow with strong southwest wind likely means that fresh wind slabs are forming, and they may become increasingly reactive throughout the day.
Summary
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
MONDAY NIGHT - Mainly cloudy with a few flurries, 5 cm / southwest wind 30-60 km/h / alpine low temperature near -6
TUESDAY - Flurries, 5-15 cm, with another 10-20 cm possible overnight / southwest wind 40-80 km/h / alpine high temperature near -2 / freezing level 1500 m
WEDNESDAY - Mainly cloudy with a few flurries, 5 cm / west wind 60-80 km/h / alpine high temperature near -2 / freezing level 2000 m
THURSDAY - A mix of sun and cloud / northwest wind 10-20 km/h / alpine high temperature near -10
Avalanche Summary
Fresh wind slabs are expected to form during the day on Tuesday may be reactive to human triggers at upper elevations.
A large (size three) cornice triggered persistent slab avalanche was reported on a large south-facing alpine slope in the Crowsnest Pass area on Thursday. This avalanche failed on weak facets overlying a hard crust deep in the snowpack and is an example of the "low probability; high consequence" scenario that persistent slab problems often create. View the MIN report HERE.
Snowpack Summary
Fresh snow and moderate to strong southwest wind may create fresh and reactive wind slabs in open areas.
The lower snowpack consists of decomposing crusts and weak, faceted snow. In the Elk Valley, a decomposing surface hoar layer can be found around one of these crusts 50-100 cm below the surface. Avalanche activity on these layers in the lower snowpack has been sporadic, mostly triggered by large loads such as a wind slab avalanche, or a cornice fall. These deeper weak layers are most likely to be human triggered on steep, rocky slopes with a shallow or thin to thick snowpack.
Terrain and Travel
- Be carefull around freshly wind loaded features.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Avoid exposure to slopes that have cornices overhead.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
Problems
Wind Slabs
Strong winds and fresh snow may form new wind slabs throughout the day on lee features in the alpine and at treeline.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Triggering large avalanches on weaknesses in the lower snowpack remains a possibility. In some areas the concern is weak snow around crusts 50 to 100 cm deep, while in others it's weak snow near the bottom of the snowpack. Human triggering of these layers are most likely in steep, rocky slopes with a shallow or thin to thick snowpack.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 12th, 2021 4:00PM
