Avalanche Canada astclair, Avalanche Canada

Cariboos Avalanche Forecast

Jan 9th, 2020 4:30PM

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

A couple of problems are in play for the region. Seek sheltered terrain to avoid wind slabs and use careful snowpack evaluation and low consequence terrain to assess and manage the problematic persistent weak layer

Summary

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength. Forecast snowfall amounts are uncertain.

Weather Forecast

Thursday night: Mostly cloudy, isolated flurries with trace accumulations, light to moderate southwest wind, alpine temperature -16 C. 

Friday: Cloudy, 10-25 cm of snow, strong south wind, alpine high temperature -10 C.

Saturday: Cloudy, 5-15 cm of snow, moderate southwest wind, alpine high temperature -10 C.

Sunday: Cloudy, 5-15 cm of snow, light south wind, alpine high temperature -18 C.

Avalanche Summary

In the aftermath of the recent storm, there have been several reports of very large (size 3) avalanches from both natural and human triggers releasing on a surface hoar layer formed in late December. These avalanches have been breaking 60-120 cm deep. 

Be sure to check out this MIN, this MIN, and this MIN for helpful illustrations of slopes that are likely to harbor this problem. A sincere thanks to the community for submitting these reports!

Freshly formed wind slabs on Friday are expected to be reactive to human triggering and will have the potential to step-down to this deeper layer, forming very large and destructive avalanches.

Snowpack Summary

Low density snow will begin to accumulate tomorrow afternoon with 10-25 cm possible. Strong south winds will likely drift this new snow into stiffer slabs on lee terrain features at higher elevations, especially near ridge crests.  

The most recent storm delivered 15-35 cm of snow across the region with southwest winds. Higher accumulations fell in the southern and eastern parts of the region. The storm snow loaded a concerning layer of surface hoar from late December, which is now buried 60-120 cm deep. Recent snowpack tests have confirmed this weak layer's propagation potential, and this layer continues to produce large avalanches across aspects and elevations. 

Terrain and Travel

  • Seek out wind sheltered terrain below treeline where you can avoid wind slabs and find great riding.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Likely

Expected Size

1 - 2

Cold, light, dry snow will begin to accumulate tomorrow afternoon with 10-25 cm possible. Strong south winds are expected to drift this new snow into stiffer slabs on lee features at and above treeline, especially near ridge crests.  

Aspects:

North, North East, East, South East, West, North West.

Elevations:

Alpine, Treeline.

Persistent Slabs

An icon showing Persistent Slabs

Likelihood

Possible

Expected Size

2 - 3.5

A concerning layer of surface hoar from late December is now buried 60-120 cm deep. This layer has produced many large avalanches across aspects and elevations, sometimes pulling back into low angle terrain. This problem warrants conservative margins with terrain decisions.

Aspects:

All aspects.

Elevations:

All elevations.

Valid until: Jan 10th, 2020 5:00PM