Avalanche Forecast

Issued: Feb 5th, 2021 4:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Persistent Slabs and Wind Slabs.

Avalanche Canada JSmith, Avalanche Canada

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Continued discipline and careful route finding will be required on Saturday to avoid triggering large avalanches on a buried persistent weak layer of surface hoar. This layer has been especially reactive at treeline elevations.

Summary

Confidence

High - The number, quality, or consistency of field observations is good, and supports our confidence.

Weather Forecast

  

FRIDAY NIGHT: Cloudy with isolated flurries; 0-3 cm. / Strong, northwest ridgetop wind / alpine low temperature -12 / Freezing level valley bottom.

SATURDAY: Snow; 5-15 cm. / Moderate, west ridgetop wind / alpine high temperature -6 / Freezing level valley bottom.

SUNDAY: Mix of sun and cloud / Moderate, northwest ridgetop wind / alpine high temperature -9 / Freezing level valley bottom.

MONDAY: Sunny / Light, northwest ridgetop wind / alpine high temperature -13 / Freezing level valley bottom.

Avalanche Summary

Numerous skier triggered slab avalanches up to size 3, failing on a weak layer of surface hoar down 60-100 cm. were reported throughout this region on Thursday.

Wednesday delivered quite a bit of human triggered avalanche activity to size 2. While all aspects were involved, the bulk of the activity was on northwest, north and northeast facing slopes between 1900 and 2300 m. This MIN from the RMR backcountry is a great representation of the widespread activity. A notable size 3 avalanche was reported from the southeast corner of the region near Balfour, BC. The skier triggered avalanche was on a north/northwest facing slope around 2000 m, it propagated across an entire drainage and may be wider than one kilometre. It likely ran on the early January surface hoar.

Persistent slabs are sitting on a very weak layer of surface hoar which is likely to be reactive to human triggers. Avalanches may be larger than expected due to the presence of this weak layer.

Snowpack Summary

Southwest switching to northwesterly winds may form reactive wind slabs on a variety of aspects at treeline and above.

70-120 cm. of recent snow is sitting on a very reactive weak layer of surface hoar which has potential to surprise backcountry users by how easily it may be triggered and how wide the persistent slabs propagate across slopes. Recent avalanches on this layer have primarily been reported at treeline and below.

A less reactive layer of surface hoar or facets buried in early January can be found down 80-130 cm.

The mid/lower snowpack is generally well settled and strong in most areas.

Terrain and Travel

  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.
  • Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.
  • Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.
  • Be careful as you transition into wind affected terrain.

Problems

Persistent Slabs

An icon showing Persistent Slabs

60-100 cm. of recent snow is sitting on a very reactive weak layer of surface hoar which has potential to surprise backcountry users by how easily it may be triggered and how wide the persistent slabs propagate across slopes. Recent avalanches on this layer have primarily been reported at treeline and below.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Likely

Expected Size

1.5 - 2.5

Wind Slabs

An icon showing Wind Slabs

Southwest switching to northwesterly winds may form reactive wind slabs on a variety of aspects at treeline and above.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1.5 - 2.5

Valid until: Feb 6th, 2021 4:00PM