Avalanche Forecast

Issued: Jan 10th, 2021 4:00PM

The alpine rating is high, the treeline rating is high, and the below treeline rating is high. Known problems include Storm Slabs and Persistent Slabs.

Avalanche Canada JSmith, Avalanche Canada

  

A widespread natural avalanche cycle is expected to begin tonight. Travel in avalanche terrain is not recommended. 

Summary

Confidence

High - We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.

Weather Forecast

  

SUNDAY NIGHT: Snow; 20-30 cm. / Extreme, south ridgetop wind / alpine low temperature -3 / Freezing level rising to 1000 m.

MONDAY: Snow; 5-15 cm, with another 15-20 cm. overnight / Strong, southwest ridgetop wind / alpine high temperature -3 / Freezing level 700 m.

TUESDAY: Snow; 5-15 cm. / Light, south ridgetop wind / alpine high temperature -4 / Freezing level 600 m.

WEDNESDAY: Flurries; 3-5 cm. / Moderate, southwest ridgetop wind / alpine high temperature -5 / Freezing level 500 m.

Avalanche Summary

A few naturally triggered wind slabs up to size 2.5 continue to be reported. Additionally, there have been numerous recent reports of "whumphing" (collapsing) on a weak layer of surface hoar down around 100 cm. See recent MIN reports HERE.

A natural avalanche cycle is expected to begin Sunday night and continue through Monday morning.

Snowpack Summary

Intense wind and snow on Sunday night is expected to form widespread storm slabs reactive to human triggers at all elevations.

Aside from this new snow, the main concerns vary throughout the region. In the Shames area, a weak layer of surface hoar has been reported in sheltered areas down around 80-140 cm. This layer may become active as the new snow load overloads the weak layer.

 A bit further north in the Nass/Sterling/Beaupre areas there is potentially still concern about an older weak layer overlying a crust that is now roughly 160 cm deep. 

In the far north of the region there is concern about weak snow at the bottom of the snowpack.

Storms like the one arriving Sunday evening often awaken deeply buried dormant weak layers, resulting in very large natural avalanches.

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
  • Watch for rapidly changing conditions during periods of heavy loading from new snow, wind, or rain.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

Problems

Storm Slabs

An icon showing Storm Slabs

New snow and extreme winds will form widespread storm slabs reactive to human triggers at all elevations.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely - Almost Certain

Expected Size

1.5 - 3

Persistent Slabs

An icon showing Persistent Slabs

New snow and extreme winds may overload deeply buried weak layers, resulting in very large avalanches. Choosing conservative terrain away from overhead hazard is the best way to manage this problem.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 3

Valid until: Jan 11th, 2021 4:00PM