Avalanche forecast

South Columbia

Feb 10 – 11, 2015Avalanche Canada
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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
    3–6
    The mid-Jan buried persistent weak layer has become reactive with recent storm loading and may remain sensitive for several more days. Smaller avalanches or cornice falls may step-down to this 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. Mostly cloudy conditions are expected but sunny breaks are possible.  Freezing levels are forecast to be around 1800m and alpine winds 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 a mix of sun and cloud. 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 during the storm. This includes both storm slabs and persistent slabs. 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

60-100cm of recent storm snow sits over the late-Jan weak layer at higher elevations. This snow is expected to be settling rapidly with the unseasonably warm temperatures. Rain has soaked the snow surface up to around 1900m 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 80-120cm and has been very reactive in some areas. The mid-December weak layer is down around 1.5m but was generally unreactive through the storm.

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