Avalanche forecast

Northwest Coastal

Apr 8 – 9, 2015Avalanche Canada
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Avalanche danger

Fri
Sat
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

The danger ratings reflect the hazard in the Northern part of the region, where a notable persistent weakness has been very touchy recently. This problem could be more widespread than we know.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–3
    Winds are expected to pick up significantly as the next system approaches. Any loose snow will blow into wind slabs in exposed lee terrain, possibly well below ridge crests. 

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–4
    The March 25th persistent weak layer should be treated with respect. It could be triggered by a smaller wind slab or a loose wet avalanche, or by a rider in the wrong spot, particularly in the Northern part of the region.

Confidence

Fair - Due to the number of field observations

Weather Forecast

Thursday: Increasing cloud with snow possible late. The freezing level is around 1400-1500 m. Winds increase to strong or extreme from the S-SW. Friday: Moderate to locally heavy snow 20-30 cm. The freezing level is near 1000-1200 m and winds are strong from the S-SW. Saturday: Cloudy with periods of snow. The freezing level is around 800 m and winds are moderate from the SW.

Avalanche Summary

Note: Almost all of the recent reported activity is from the Northern part of the region near Ningunsaw Pass. This could be because this is the hot spot at the moment, but it could also be because there are few observers in the field further south. For the past few days, there have been reports of natural, skier-triggered, and remotely triggered slabs up to size 3 releasing on the March 25th surface hoar layer. Some of these have been triggered from below or in low-angle terrain. In addition, cornices have been failing and loose wet activity has been noted in the afternoon, both of which have triggered deeper persistent slabs.

Snowpack Summary

The snow surface varies from dry faceted powder and/or surface hoar on shady slopes, to moist snow or a sun crust on sunny slopes. In some places down-flowing winds have created thin wind slabs in lee features lower down the mountainside. Approximately 40-70 cm of snow sits above the March 25th surface hoar layer. This interface seems much touchier in the northern part of the region, but has been reported throughout the northwest coastal area. The early March facet/crust persistent weakness is now down over a metre and produces hard, sudden planar results in snowpack tests.

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