Avalanche forecast

Northwest Inland

Feb 4 – 5, 2015Avalanche Canada
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Avalanche danger

Fri
Sat
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

The highest avalanche danger will likely be Thursday night. If the storm arrives early Thursday, the danger could quickly rise to high in the alpine.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–5
    The late-Jan crust is down 60-80cm and may still be reactive in some areas. In the mid-pack there are older persistent weak layers but these have generally stabilized. Extra caution is required in thinner snowpack areas, especially the north.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–4
    New snow will add to the existing 20-30 cm of recent storm snow which is likely settling into a slab.  Strong to extreme SW winds may form large wind slabs in exposed terrain.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    3–6
    Although less likely to trigger, recent avalanche activity suggests weak layers buried at the beginning of the winter should still be our radar, especially in the north of the region.

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

The storm system that's expected to batter the coast should limp into the inland Thursday afternoon.  While the snow totals aren't all that impressive, the wind values are.  I expect 5 - 10 cm of snow Thursday and another 5 - 10 cm Thursday night with alpine winds creeping into the triple digits out of the SW.  Winds are expected to be extreme in the alpine and more moderate at treeline right through the weekend.  As for snow totals, friday offers 2 - 5 cm and Saturday looks to be about the same. 

Avalanche Summary

Small wind slabs near ridge crest were reported Tuesday to size 1.  On Monday, natural and human-triggered avalanches size 1 to 1.5 were reported in the south of the region. These were 20-30cm thick in sheltered areas and 30cm+ in wind loaded features. Sluffing from steep terrain was also reported.

Snowpack Summary

20 - 30cm of new snow has fallen in the last couple days. Strong winds have redistributed this snow in exposed terrain forming winds slabs in leeward features and stripping exposed slopes. The late-January crust is typically down 60-80cm in the south of the region and probably around half this depth in the north. Tests are indicating that this interface is generally well bonded, but isolated avalanches have been reported to have released on this layer recently. The mid-January rain crust and/or surface hoar layer is down over 1m in the south and has generally become inactive. It may still be a concern in thinner snowpack areas, at higher elevations, and in the far north of the region. Near the base of the snowpack is a crust-facet combination buried in November. This deep persistent weakness was recently reactive and may still be touchy in the far north of the region. Wherever you are, I'd be cautious of this deep and potentially destructive layer. Possible triggers include thin spot triggering in high elevation terrain, a cornice fall, or a smaller avalanche stepping down.

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