Avalanche forecast

Purcells

Feb 10 – 11, 2015Avalanche Canada
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Archived · expired 12 years ago

Avalanche danger

Thu
Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Residual storm instabilities may still be a concern, especially in the alpine. Avoid steep unsupported slopes and wind-loaded features. If the sun comes out, use extra caution on south-facing slopes.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–5
    Buried persistent weak layers have become very reactive with recent storm loading and may remain reactive to human-triggering for several more days. Smaller avalanches or cornice falls may step-down to these layer resulting in very large avalanches.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    2–5
    Strong winds, heavy snowfall, and high freezing levels over the weekend created widespread storm slabs at higher elevations. These slabs are expected to be gaining strength but may remain reactive to human-triggering for several days.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    1–3
    Loose wet avalanches are possible from steep terrain features where the snow surface is moist. If the sun comes out, sluffing from steep sun exposed slopes is possible.

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

A dirty ridge of high pressure should keep things mainly dry on Wednesday but light scattered flurries are possible. A mix of sun and cloud is expected with freezing levels around 1800m. Alpine winds are forecast to be light-to-moderate from the SW. On Thursday, a mix of sun and cloud is expected with light scattered precipitation. Freezing levels are forecast to rise to over 2000m. On Friday, dry conditions are expected with mainly sunny conditions. Freezing levels may peak on Friday at around 3000m.

Avalanche Summary

Widespread natural, human-triggered, and explosive controlled avalanches up to size 3 were reported on Friday through Monday. This includes storm slabs and persistent slabs. On Sunday, a skier was involved in an accident in the Canyon Creek area. The subject was caught in a size 2.5 persistent slab which resulted in serious injuries. The avalanche released on the mid-January surface hoar layer down around 80cm. On Tuesday, explosive triggered a size 2.5 avalanche on the November crust/facet layer. This occurred in an area that had previously slide and then reloaded. On Wednesday, natural activity is generally not expected but is possible on steep south-facing slopes if the sun comes out. Human-triggering of the storm slab remains possible, especially on steep slopes and wind loaded features in the alpine.

Snowpack Summary

40-60cm of rapidly settling storm snow sits over the late-Jan weak layer at higher elevations. Rain has soaked the snow surface up to around 2000m and moist snow is reported to at least 2200m. Overnight cooling may be forming a surface crust at some elevations. Strong SW winds had formed wind slabs in exposed leeward terrain features. The storm slab sits on an old rain crust at lower elevations, variable surface hoar, and/or wind affected surfaces at higher elevations. The mid-January surface hoar is typically down 50-80cm and has been very reactive in some areas. The mid-December weak layer is down around 1m but its reactivity has been isolated recently. The mid-November weak layer of crusts and facets can still be found near the bottom of the snowpack. It has generally been unreactive but one explosive triggered avalanche occurred on it recently in a reloaded area that had slide previously.

Regions covered