Avalanche forecast

South Coast

Feb 5 – 6, 2016Avalanche Canada
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Avalanche danger

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

Stormy conditions have elevated the avalanche danger to HIGH. Touchy storm slabs may take some time to settle and bond.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    3–6
    Buried persistent weaknesses may have been destroyed in most areas, but remain cautious in high elevation terrain (particularly in the north of the region) where this problem may be lingering. New storm loading may release or step down to this layer.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–4
    New storms slabs continue to develop with strong southerly winds and heavy snowfall.

Confidence

Moderate - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

Strong southerly winds and heavy precipitation overnight with the freezing level at about 1500 metres. Snow ending Saturday morning as the storm moves to the east, winds becoming moderate westerly and temperatures cooling as freezing levels drop to about 600 metres. Light southwest winds on Sunday with broken skies in the afternoon and freezing levels rising rapidly to 2500 metres. Clear skies and light southwest winds on Monday with freezing levels around 3000 metres.

Avalanche Summary

No recent avalanches reported. I suspect that storm slabs developed on Friday, but poor visibility and travel conditions limited observations. On Tuesday a skier remotely triggered a size 3.0 slab avalanche from 20 metres away that released on the early January surface hoar. This avalanche happened at 2300 metres on a south-southeast aspect in the Duffey Lake area. The fracture propagated 350 metres and ran 750 metres to the valley bottom.

Snowpack Summary

New storm slabs developed during the day on Friday. In the south, 40-70 cm of recent storm snow sits on a widespread and generally supportive rain crust that was buried on Jan. 28. The bond to the crust appears to be fairly good but at least one notable storm snow weakness was observed 10 cm above the crust. Fresh pockets of wind slab may also form in immediate lee features. The combination of heavy storm loading, rain, and warm temperatures likely flushed out the mid-January persistent weakness in most areas in the Cascades. Further north, generally 20-40 cm of dry storm snow overlies the late-Jan rain crust below around 1800-2000 m. Above this elevation the new snow sits on settled storm snow or previously wind affected surfaces. Fresh pockets of wind slab are likely in exposed lee terrain. Where it still exists, the mid-January surface hoar layer is between 60 and 130 cm below the surface. This persistent weakness could be lingering on higher elevation slopes that did not previously avalanche and triggering remains a concern.

Regions covered