Avalanche Forecast
Regions: South Columbia.
The recent storm was a massive one and the snowpack may take longer than usual to recover, especially with the presence of persistent weak layers. Choose conservative terrain and minimize overhead exposure to avalanche terrain as the potential still exists for large avalanches.
Confidence
Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.
Weather Forecast
MONDAY NIGHT - Cloudy with clear periods and scattered flurries / southeast wind, 10-30 km/h / alpine low temperature near -9
TUESDAY - Cloudy with sunny periods and isolated flurries / southeast wind, 10-30 km/h / alpine high temperature near -8
WEDNESDAY - Cloudy with sunny periods / light northeast wind / alpine high temperature near -7
THURSDAY - A mix of sun and cloud / light southwest wind, 20-50 km/h / alpine high temperature near -8
Avalanche Summary
The recent storm was a significant one, and there is a great deal of uncertainty at this time as to how quickly the snowpack will gain strength. Avalanche occurrences are beginning to taper, but recent avalanches have been very large. Patience and conservative terrain selection is the name of the game right now.
There have been numerous reports every day since Thursday of natural, human and explosives triggered avalanches up to size 3.5. Many of these have been triggered remotely.
Snowpack Summary
The South Columbias have seen 60-100 cm of new snow since Thursday night. Storm slabs are likely widespread and may be reactive to human triggering.
There is anywhere from 100-160 cm of snow on top of a widespread layer of large, feathery surface hoar crystals. This layer is suspected to have been responsible for numerous recent avalanches and it may continue to be reactive to human triggers.
A weak layer that formed in late November is now over 160 cm deep. This is the layer of concern relating to the listed persistent slab avalanche problem. The weak layer may present as surface hoar, a crust, facets or a combination, depending on elevation and aspect.
Terrain and Travel
- Make conservative terrain choices and avoid overhead hazard.
- Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Avalanche Problems
Storm Slabs
Storm slabs could still be triggered by humans, especially in wind loaded areas.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible - Likely
Expected Size: 1 - 2.5
Persistent Slabs
There is a weak layer of surface hoar down 100-160 cm. Numerous recent avalanches have occurred on this layer and human triggering is a possibility.
Another weak layer that formed in late November is now down over 170 cm. This layer could be triggered from shallow snowpack areas, and it is also possible for avalanches triggered on the shallower layer to step down to this layer, resulting in very large avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Unlikely - Possible
Expected Size: 2 - 3.5