Avalanche forecast

Northwest Coastal

Jan 3, 2017Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Expect change to be slow due to cold temperatures. Persistent slab avalanches will continue to be a problem for human triggering.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2
    Forecast extreme northeast winds are expected to shift loose surface snow into stiff new wind slabs in exposed lee terrain. Watch for areas that were previously scoured and may become reverse-loaded as the winds switch direction.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–3
    Surface hoar that was buried last week continues to be sensitive to human triggering in the Terrace area. This problem may be more widespread across the southern half of the region. Please submit your observations to the MIN.

Confidence

Moderate -

Weather Forecast

Clear and cold overnight with strong northeast winds. The air in the alpine is expected to be 5-10 degrees warmer than the valleys. Clear and cold on Tuesday with strong northeast winds. Clear and cold on Wednesday with a chance of above freezing temperatures in the alpine. Cloud developing on Thursday with warmer temperatures and a switch to westerly winds.

Avalanche Summary

On Monday, in the north of the region near Ningunsaw a natural size 3.5 was reported that released on basal facets and ran full path. On Sunday, new wind slabs that formed from reverse loading on south aspects were reported to have released naturally up to size 2.5 in the south of the region. In the north, one size 2.0 natural persistent slab was reported that released down to the ground exposing a bed surface of rock slab.

Snowpack Summary

Recent storms deposited 50-80 cm of snow combined with strong winds, most recently from the north. The storm snow overlies a layer of feathery surface hoar (up to 15 mm in sheltered areas) buried on December 25, making wide propagations possible. Ongoing reports indicate this combination of layers is susceptible to easily triggered avalanches, including avalanches running in low angled terrain. An earlier (and therefore deeper) weak interface that formed during the early December cold snap can be found in isolated areas buried 100-150 cm deep. The layer consists of preserved surface hoar or weak faceted (sugary) snow. The lower snowpack is well consolidated in deep snowpack areas. In shallow snowpack areas, especially north of Ningunsaw, an old rain crust near the bottom of the snowpack has developed weak facets and might be triggerable from a thin or rocky area on a convex slope.

Regions covered