Avalanche forecast

Northwest Coastal

Jan 27, 2017Avalanche Canada
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Avalanche danger

Fri
Sat
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Developing avalanche danger is expected to reach HIGH in the alpine on Friday. If the storm arrives early danger may reach HIGH at all elevations.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3
    It may still be possible to trigger avalanches on buried weak layers (Dec 25, Jan 5th, Jan 12th surface hoar) ...or have a smaller avalanche 'step down' and trigger one of these layers. The new storm will be a good test for these weak layers.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3
    Storm slabs are expected to develop with forecast new snow and wind. Avalanche size and frequency will increase with each pulse of precipitation, increasing winds, and rising freezing levels.

Avalanche Summary

No new avalanches reported. One report on Wednesday of a skier triggered wind slab size 1.0 on a convex roll at 1500 metres that was about 25cm deep. Expect avalanche size and frequency to increase as the forecast storm moves into the region.

Confidence

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

Weather Forecast

Stormy weather for the next few days. Overnight: Extreme southwest winds combined with 10-20 cm of new snow and freezing levels around 800 metres. Friday: Extreme south winds, 20-30 cm of new snow during the day and another 20-40 cm overnight, freezing level 1000 metres. Saturday: another 25-40 cm of new snow combined with extreme south winds and freezing levels rising to 1500 metres. Sunday: Winds becoming moderate to strong southwest combined with 10-20 cm of new snow and dropping freezing levels.

Snowpack Summary

There is 10-20 cm of new snow above the latest buried surface hoar layer from January 23rd that has been found up to size 10 mm at treeline and below. This surface hoar layer may be associated with a crust below 1100 metres. There continues to be several other surface hoar layers of concern from early January and Christmas. Some reports show these persistent weak layers to be rounding and bonding, however we are still getting some reports of sudden planar releases in snowpack tests with hard forces applied. I suspect the forecast heavy precipitation over the next few days will be a good test for these older buried weak layers.

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