Avalanche forecast

North Columbia

Dec 24 – 25, 2019Avalanche Canada
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Avalanche danger

Thu
Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

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.

Avalanche problems

  • Persistent Slabs

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

    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.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–2.5

    Storm slabs could still be triggered by humans, especially in wind loaded areas.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

MONDAY NIGHT - Cloudy with clear periods / southeast wind, 10-30 km/h / alpine low temperature near -11

TUESDAY - Cloudy with sunny periods and isolated flurries / southeast wind, 20-40 km/h / alpine high temperature near -10

WEDNESDAY - A mix of sun and cloud / light northeast wind / alpine high temperature near -10

THURSDAY - A mix of sun and cloud / light southwest wind, 20-50 km/h / alpine high temperature near -9

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 tapering, but recent avalanches have been very large. Patience and conservative terrain selection is the best way to manage this uncertainty.

On Sunday, there were dozens of reports of natural, human and explosives triggered avalanches up to size 4. These were a mix of storm slab and persistent slab avalanches.

On Thursday, Friday and Saturday, there were numerous reports of natural, human and explosives triggered avalanches up to size 3.5. A number of these were triggered remotely.

Snowpack Summary

The North Columbias received upwards of 80 cm between Thursday night and Saturday night. Storm slabs are likely widespread and may still be reactive to human triggers.

There is anywhere from 100-160 cm of snow on top of a widespread layer of large, feathery surface hoar crystals. This layer has reportedly been responsible for numerous recent avalanches and may be reactive to human triggers.

A weak layer that formed in late November is now over 170 cm deep. This is the layer of concern relating to the 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.

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