Avalanche forecast

Purcells

Mar 20 – 21, 2013Avalanche Canada
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Archived · expired 14 years ago

Avalanche danger

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

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–7
    Storm snow, wind loading or cornice fall may overload a persistent weakness buried in the upper snowpack. This could lead to surprisingly large avalanches.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–6
    Storm slabs continue to develop due to strong winds and new snow. Thick pockets of wind transported snow are expected to continue to develop at higher elevations. Cornice growth may be extensive and weak during the storm.

Confidence

Fair - Forecast snowfall amounts are uncertain on Thursday

Weather Forecast

Overnight and Thursday: Winds becoming Westerly moderate to strong overnight as the snow continues to fall across the region. Expect another 5-10 cms overnight and another 3-5 cms during the day. Alpine temperatures should drop down to near -10.0, and the freezing level should be at valley bottoms.Friday: Unsettled weather with mostly cloudy skies and strong to very strong gusty Northwest winds. Continued cool temperatures in the alpine and freezing levels rising to about 1000 metres during the day.Saturday: A ridge of High pressure is moving into the region bringing light West winds, clearing skies, and alpine temperatures in the -10.0 - -15.0 range.

Avalanche Summary

Explosives control released cornices that triggered slabs on the slopes below up to size 3.0 before the new storm. Expect new cornice growth to be weak, and may fall off naturally.

Snowpack Summary

Strong winds overnight and moderate winds during the day combined with new snow have created a new storm slab on all aspects. Deep pockets of wind transported snow are developing in the alpine and at treeline. Deep storm slabs which formed last week are slowly gaining strength. Cornices are large. A weak layer of surface hoar and/or a crust is buried down about 50-120 cms in the alpine and treeline elevations. This surface hoar layer is producing variable results in snow profile tests, and continues to be a concern for professionals. This layer may linger with ‘low probability/ high consequence’ type character. Testing for this interface in your local area should help you gain (or lose) confidence before committing to aggressive terrain. A facet/crust layer sits at the base of the snowpack in some places.

Regions covered