Avalanche forecast

South Columbia

Dec 21 – 22, 2015Avalanche Canada
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Avalanche danger

Wed
Thu
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

The wind effect from the last storm seems to be highly variable. The best (and safest) riding may be found on sheltered slopes at treeline and below.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–3
    Recently formed wind slabs should strengthen gradually over the next few days. While that happens, I'd stick to sheltered lower elevation slopes where the riding is better (and safer).

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–4
    A layer of buried surface hoar can be found between 1400m and 1800m. Although this layer has become less likely to trigger, I'd remain cautious on steep roles in cut-blocks and open glades below treeline.

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

A fairly benign weather pattern is setting up for the forecast period. Light flurries are expected for Tuesday, but snowfall amounts shouldn't exceed 5cm. Isolated flurries with occasional sunny breaks are forecast for Wednesday and Thursday. Ridgetop winds are forecast to remain mainly light for all 3 days while alpine temperatures should hover between -12 and -15.

Avalanche Summary

On Sunday, we received a few reports of widespread natural and human-triggered wind slab avalanche activity to size 2. As the weather eases, so should natural wind slab avalanche activity. That said, human triggering will remain a concern for a few days.

Snowpack Summary

Throughout the weekend there was up to about 70cm of new snow in the Monashees and slightly less in the Selkirks. Strong to extreme southerly winds have redistributed much of this snow into deeper wind slabs in exposed lee features in the alpine and at treeline. In more sheltered terrain, I would expect deep powder and really good riding. Between 80 and 150cm below the surface you'll likely find a weak layer of well-developed surface hoar. This layer is most widespread and reactive at lower elevations (between 1400m and 1800m.) Snow pit tests suggest that human triggering of this interface has become unlikely. That said, if it does fail the overlying slab is stiff enough to propagate over a wide distance. Below this layer, the snowpack is thought to be generally strong and well-settled.

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