Avalanche forecast

South Coast

Apr 17 – 18, 2015Avalanche Canada
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Avalanche danger

Sun
Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
1 · Low
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Highlights

Solar radiation and rising temperatures will destabilize the snowpack. Copy this link and check out the new blog post for this region: avalanche.ca/blogs/VTAw_CcAAIUPxFdk/south-coast-problems

Avalanche problems

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    3–5
    Recent cornice growth has been observed and large cornices are expected to become weak with solar radiation and daytime warming. Cornices could trigger large slab avalanches.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    2–5
    Two persistent weak layers sit in the upper snowpack. One is down 20-50 cm and has been recently reactive naturally and to human triggers. The second one sits 50-150 cm down and may re-awaken with warming, cornice fall and step down avalanches.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–3
    Solar radiation and rising freezing levels will deteriorate the snowpack. Travel on sunny slopes early, and watch for obvious signs of instabilities like avalanches, moist surface snow and snowballing.

Confidence

Poor - Due to the number of field observations

Weather Forecast

A dominating high pressure ridge is building over Southern BC. This will bring summer-like temperatures through the weekend with alpine temps rising to 12 degrees! Saturday and Sunday will be mostly sunny skies. Alpine temperatures rising to 5-12 degrees and freezing levels near 2700 m. Ridgetop winds will be light from the WNW. By late Monday, the ridge starts to break down allowing a more seasonally westerly flow.

Avalanche Summary

On Thursday no new observations reported. On Wednesday, natural cornice fall was reported, pulling thin slabs up to size 1 from the slopes below. Strong solar radiation and warming expected through the forecast period will likely initiate a natural avalanche cycle. Watch overhead hazards like cornice failures and solar induces loose wet, and slab avalanches.

Snowpack Summary

Anywhere from 20 to 40 cm of recent storm snow sits on a persistent weak layer comprising of crusts, surface hoar and facets which were buried April 10th. Moderate to strong south west winds are redistributing the storm snow into wind slabs on leeward slopes and terrain features. The mid-March persistent weak layer of facets on a crust is now approximately 50-100 cm down and continues to sit dormant. There is a low probability of triggering this layer, however; if it is triggered the consequence would be high. Large looming cornices may become weak with solar radiation and daytime warming. If a cornice fails it could trigger a large avalanche from the slope below.

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