Avalanche forecast

South Columbia

Dec 30 – 31, 2011Avalanche Canada
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Avalanche danger

Sun
Mon
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–5
    Consistent strong south westerly winds have blown around new snow and loaded open, lee slopes at treeline and in the alpine. You may even find wind effected snow in open areas below treeline.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–6
    Increased load in the form of wind, rain, snow or a recreating human may trigger an avalanche originating in this weak layer. If triggered, avalanches will likely be large, destructive and un-manageable.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–5
    Storm slabs can run far, fast & be destructive. The slabs are sitting on two weak layers in the upper 100cms of the snowpack. The weight of the slab may trigger the initial weakness, then step down to the deeper layer creating large avalanches.

Confidence

Good - -1

Weather Forecast

One last pulse out of the recent active weather system will affect the region Friday evening before a strong ridge of high pressure anchors itself over Eastern BC for the weekend. Skies clear and cooler temperatures pervade under the ridge which will bring freezing levels down to valley bottom. On Saturday you can expect moderate winds out of the W and a daytime high of -9 with overnight lows dropping slightly to -12. A weakening system slides into the region Monday bringing light precipitation and cloudy skies.

Avalanche Summary

Reports of natural large avalanches up to size 3 have occurred throughout the South Columbias. Continued reports of rider triggered avalanches up to size 1.5, and natural cornice failures triggering slopes below up to size 2.5. The focus is on elevations between 1300-2100m, and mainly on North-South aspects. This avalanche cycle indicates that the December 24th surface hoar and the mid-December surface hoar layers have reached the tipping point and are producing large slab avalanches. Check out the Forecasters Blog to see an updated avi picture. It clearly indicates how touchy the surface hoar layer is on convexities and low angle terrain.

Snowpack Summary

Up to 100 cm have fallen across the region since Boxing Day. This meter of snow sits on top of a weak layer that is widespread across the region; the mid December surface hoar/facet/crust combination. In tests this layer fails with sudden planer characteristics meaning that the failure has a lot of energy in it. This layer can be found at all three elevation bands and is still quite active. This layer will continue to be reactive to increased load in form of snow, rain, wind or a recreating human. Below the mid December weak layer lies a well consolidated & strong mid pack.

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