Avalanche forecast

Purcells

Mar 14 – 15, 2013Avalanche Canada
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Archived · expired 14 years ago

Avalanche danger

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

Precipitation amounts vary a lot throughout the region and according to altitude. Be aware of conditions that are specific to your area and make observations continuously as you travel.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    2–7
    A significant load like the forecasted rain/heavy snow or a cornice fall could trigger the surface hoar and a sun crust layer buried down 80-100 cm .

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1–6
    Warm and wet storm has created and is going to keep developing storm slabs, new wind slabs lee of strong SW-W winds in the alpine, loose dry avalanches above 2300 m. and wet slab and loose avalanches below that level.

Confidence

Fair - Forecast snowfall amounts are uncertain on Friday

Weather Forecast

Thursday night and Friday: Freezing levels will start to drop (1500 m.) bringing the snow line lower. Moderate amounts are expected until Friday and will taper off becoming light during the day. Moderate to strong winds should switch from the SW to the W.Saturday: Unsettled conditions without any frontal systems bringing very light precipitation, strong W winds, mainly cloudy skies and freezing levels near 1000 m.Sunday: Similar pattern as Saturday with cooler temperatures and lighter winds.

Avalanche Summary

I suspect that a natural avalanche cycle is ongoing in the region. Slab avalanches up to size 3 have been reported out of alpine features especially on N-NW-NE aspects. Loose avalanches were also reported up to size 1.5 in the recent snow. 

Snowpack Summary

The warm storm has left from 20 to 45 cm of snow above 2000 m..  At higher elevations, snow has been transported by strong SW and W winds creating windslabs that are very touchy. Below the freezing line, the snowpack is rain soaked. Another pulse of precipitation will add weight onto the storm slab and the already moist/wet snowpack.  The new snow has not been bonding well to the underlying surfaces creating lots of recent avalanche activity, easy snowpack test results and reactivity to skier traffic. Some of the significant underlying surfaces mentioned before include a surface hoar layer in shaded-sheltered areas, a suncrust on S aspects and a melt-freeze crust below 1700 m. The surface hoar persistent weak layer buried down 100 cm is also still a concern to professionals and would generate very large avalanches if triggered.

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