Avalanche forecast

South Rockies

Mar 15 – 16, 2015Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
4 · High
Treeline
3 · Considerable
Below
1 · Low
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Highlights

Forecast heavy snow and wind will result in high avalanche danger.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–4
    Forecast heavy precipitation combined with wind is expected to result in new storm slabs on all aspects in the alpine and at treeline.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    3–6
    Recent very warm temperatures followed by heavy rain, and then the forecast snow and wind, may be too much change for the snowpack to manage. Avalanches releasing on the deeply buried weak layers are expected to be large and destructive.

Confidence

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

Weather Forecast

Snow above 1000 metres combined with moderate southwest winds tonight and Monday morning. 15-30 cm of snow is forecast for alpine elevations by late Monday morning. Monday should be cloudy with some lingering flurries and light easterly winds. Freezing levels should drop down to valley bottoms by Tuesday morning. Mostly sunny with light winds on Tuesday and freezing levels rising up to about 2000 metres. Cloudy on Wednesday with moderate southwest winds and light precipitation.

Avalanche Summary

No new avalanches reported. I expect that forecast new snow and wind will develop new storm slabs in the alpine and at treeline on all aspects.

Snowpack Summary

Up to 40 mm of rain fell on Saturday that may have been snow above 2000 metres. Gradual cooling and forecast heavy precipitation for Sunday night and Monday are expected to develop new storm slabs above various old surfaces including moist or wet snow, crusts, old windslabs, and possibly surface facets on high alpine north aspects. There is not enough snow at below treeline elevations for avalanches at this time. If the freezing levels drop to valley bottom we may see new snow covering some areas that have been bare ground. The most prominent snowpack feature is a thick crust 10-30cm below the surface (before the ongoing storm), extending up to around 2200m elevation. The support of this crust is breaking down in response to warm temperatures. Persistent weak layers below this crust still react in snowpack tests and could wake up with continued warming or loading.

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