Avalanche forecast

South Columbia

Jan 16 – 17, 2015Avalanche Canada
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Avalanche danger

Sun
Mon
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

New storm problems combined with the persistent slab problem means tricky conditions for the weekend.  Use a conservative approach if you are heading into the mountains.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–3
    Soft wind slabs have likely formed in leeward features in the alpine and in isolated areas at treeline. 

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    3–6
    The mid-December weak layer remains problematic at and just below treeline where the snowpack structure may still be primed for human triggering in some areas. The weight of the new snow may increase the reactivity of this layer.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–2
    The new snow sits on a layer of large surface hoar. Fast sluffing from steep terrain may run farther than normal.

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain on Sunday

Weather Forecast

A weak ridge of high pressure will keep the interior dry for Friday night and Saturday morning. Light flurries are expected Saturday afternoon with moderate SW alpine winds. Freezing levels should be at around 1000m. On Sunday, another frontal system will cross the interior bringing 10-20mm of precipitation and moderate-strong SW alpine winds. Freezing levels may reach around 1500m. Lingering flurries are expected for Monday a ridge of high pressure begins to build over the interior.

Avalanche Summary

On Thursday, a natural cornice fall triggered a size 1 persistent slab which released on the mid-Dec layer. On Wednesday, explosives triggered a cornice but the cornice did not trigger a slab. On Tuesday, a natural size 2.5 persistent slab was reported. This released on the mid-Dec weak layer.  Some natural avalanche activity is possible on Saturday in specific areas including fast sluffing from steep terrain and wind slabs in leeward alpine features. Small avalanches have the potential to step down and trigger a persistent slab which would greatly increase the consequences. Skier triggering is likely in wind loaded areas and steep terrain, and remains possible for persistent slabs where the tricky mid-December layer is still intact.

Snowpack Summary

The new snow has buried widespread 10-20mm surface hoar, a sun crust on steep sun exposed slopes, and/or wind affected surfaces in the alpine. The problematic mid-December surface hoar/crust layer is typically down 80-120cm below the new snow and remains sensitive to human triggering is some areas. The reactivity of this persistent weak layer appears to be quite variable but still has the potential for large, destructive avalanches in some areas. The layer appears to be the most reactive at and below treeline.

Regions covered