Avalanche forecast

South Columbia

Jan 9 – 10, 2021Avalanche Canada
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Avalanche danger

Mon
Tue
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Don't let sunny skies and good snow lure you into complex terrain. Recent human triggered avalanches have been large. Avalanche danger may be improving as the likelihood of triggering them diminishes, but if you're unlucky enough to do so, consequences can be high.

Avalanche problems

  • Wind Slabs

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

    Recent snow and moderate wind have created deep pockets of reactive wind slab in lee terrain features at upper elevations. There have been several instances of human triggered wind slab avalanches around size 2 in the last few days.

  • Persistent Slabs

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

    A weak layer of surface hoar that was buried around Christmas is now down about 40-80 cm and is most prevalent at treeline and below treeline. This layer remains at a depth triggerable by skiers, sleds and wind slab avalanches.

    A deeper persistent weak layer buried in early/mid-December is now down 90 to 150 cm. The form and distribution are highly variable and have may vary significantly from one valley to the next, and between elevation bands. Triggering these layers require large loads such as explosives or other avalanches in motion. The result of a step down to these layer would be large and destructive.

Terrain and Travel

  • Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
  • Avalanche hazard may have improved, but be mindful that deep instabilities are still present.
  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

Confidence

High - The number, quality, or consistency of field observations is good, and supports our confidence. Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

Friday night: Partly cloudy, light west wind, freezing level valley bottom.

Saturday: A mix of sun and cloud, light southeast wind, alpine high -7, freezing level valley bottom.

Sunday: Increasing cloud, light southeast wind, alpine high -7, freezing level valley bottom.

Monday: Flurries, trace, light to moderate southeast wind, alpine high -6, freezing level 800 m.

Avalanche Summary

Recent avalanche activity has been widespread, large (size 2+), running on a variety of weak layers and triggered both naturally and by humans.

  • Natural storm/wind slab - Numerous natural storm/wind slab avalanches have been observed in the last few days on all aspects at alpine and treeline elevations, averaging size 2.

  • Human triggered - Thursday and Friday were eventful days for human triggered avalanches in the busiest areas of the region. RMR slackcountry saw four size 1.5-2 skier triggered avalanches, including a partial burial. Check out some of these MIN reports here, here and here. Crowns ranged from 30 to 70 cm, likely running on the most recent storm interface at the shallow end, and on the Christmas persistent layer at the deeper end.

  • Persistent slab - On Wednesday and Thursday, there were four natural persistent slab avalanches size 2.5-3 reported in the region on northerly aspects in the alpine. Three of these were reported to have run on the early December persistent weak layer.

Snowpack Summary

Around 40-80 cm of recent snow sits on a weak layer of surface hoar that was buried around Christmas. This layer is most prevalent at and below treeline. Previous moderate to strong winds have redistributed surface snow, creating wind slabs at wind exposed elevations.

A couple of persistent weak layers buried in early/mid-December are down about 90-150 cm. Generally, they can be found as a layer of surface hoar above in close proximity to a crust/surface hoar layer. The form and distribution of these layers are highly variable and conditions may differ significantly from one valley to the next. 

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