Avalanche forecast

South Rockies

Jan 16 – 17, 2014Avalanche Canada
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Avalanche danger

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

Forecast very warm temperatures are an added concern to a complex snowpack

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–4
    Very strong winds have created hard wind slabs in the alpine and at treeline. These hard wind slabs may be more than a metre thick. Forecast very warm temperatures and strong solar radiation may increase the likelihood of triggering.

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3
    Cornices may become weak and fall off naturally due to strong solar radiation and forecast warm alpine temperatures. Cornice falls are a large load that may release buried persistent weak layers on slopes below, resulting in very large avalanches.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3–6
    Recent storm snow and hard wind slabs have been added to the load above buried weak layers. Deeply buried weak layers may become harder to trigger, but the consequences are very large destructive avalanches.

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

Overnight and Friday: Temperatures are expected to rise overnight at higher elevations, and drop down to close to freezing at 1600 metres. Upper elevation winds should continue to be moderate to strong Westerly, and below treeline winds should be light. Some cloud on Friday may limit solar radiation.Saturday: Clear, sunny, and very warm in the alpine with light Westerly winds. Expect +5 degrees in the alpine with strong solar radiation.Sunday: Building Southwest winds with a bit of cloud cover and cooler temperatures in the alpine. Freezing level about 1700 metres.

Avalanche Summary

No new avalanches reported. Suspect extreme Westerly winds and warm temperatures have developed hard wind slabs. Areas with snow available for transport may have continued to experience natural wind slab avalanches. Forecast warm temperatures, limited precipitation, and continued very strong winds are expected to develop hard wind slabs and decrease natural avalanche activity. Avalanches that are triggered are expected to be large due to the amount of recent storm snow. Large storm snow avalanches may step down to buried persistent weak layers resulting in very large destructive avalanches.

Snowpack Summary

Expect extensive wind transport and wind slab development in all areas of the region. Recent storm snow varies from 40-70 cm across the region and I suspect that in some alpine areas storm snow has been transported into slabs that are more than a metre thick. Persistent weak layers of buried crusts/facets/surface hoar continue to be a concern, and may have been the failure plane for recent large natural avalanches. Forecast very warm temperatures may result in loose wet avalanches or cornice falls that may trigger the persistent weak layers or the basal depth hoar. Strong solar radiation combined with above freezing temperatures in the alpine could create very touchy triggering on Southerly aspects.

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