Avalanche forecast

North Columbia

Jan 3 – 4, 2021Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

New snow, wind, and rising Freezing levels have created widespread and reactive storm slabs. Large human triggered avalanches are LIKELY at all elevations on Sunday and very large avalanches on deeper weak layers are possible.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3.5

    Two persistent weak layers buried in early/mid Dec. are now 80 to 150 cm below the surface. The form and distribution of these layers are HIGHLY VARIABLE and have created conditions that can vary significantly from one valley to the next .

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1.5–2.5

    New snow, strong winds and rising freezing levels have created widespread storm slabs ripe for human triggers.

Confidence

Moderate - Uncertainty is due to the limited number of field observations. Forecast precipitation (either snow or rain) amounts are uncertain.

Weather Forecast

  

SATURDAY NIGHT: Snow; 10-15 cm. / Strong, southwest ridgetop wind / alpine low temperature -4 / Freezing level 800 m.

SUNDAY: Flurries; 3-5 cm. / Moderate, west ridgetop wind / alpine high temperature -6 / Freezing level 1200 m.

MONDAY: Cloudy with isolated flurries; 0-3 cm. / Moderate, southwest ridgetop wind / alpine high temperature -8 / Freezing level 800 m.

TUESDAY: Mix of sun and cloud / Light, southwest ridgetop wind / alpine high temperature -7 / Freezing level 1000 m.

Avalanche Summary

On Saturday, a skier triggered a size 2 slab avalanche near the Gorge area. See the excellent MIN report Here.

Large human triggered storm slab avalanches are LIKELY at all elevations on Sunday.

Snowpack Summary

Up to 20 cm of new snow, moderate to strong winds, and rising freezing levels on Saturday have created widespread storm slabs ripe for human triggers. 

Two persistent weak layers buried in early/mid Dec. are now 80 to 150 cm below the surface. The form and distribution of these layers are HIGHLY VARIABLE and have created conditions that can vary significantly from one valley to the next. The first layer down around a metre has been primarily reported as small surface hoar. 

The next layer has been reported as a thin freezing rain crust, surface hoar, or thick rain crust depending on elevation and location. As a result, diligent investigation of the snowpack is required to get a handle on local conditions. Forecast snowfall for the weekend may reignite avalanche activity at these deeply buried interfaces.

Terrain and Travel

  • Uncertainty is best managed through conservative terrain choices at this time.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Avoid traveling in runout zones. Avalanches have the potential to run to the valley floor.

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