Avalanche forecast

Northwest Coastal

Dec 14 – 15, 2017Avalanche Canada
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Avalanche danger

Sat
Sun
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Snowfall amounts vary across the region. New storm slabs and dry loose surface avalanches are the name of the game.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–2
    New storm slabs will likely build through the forecast period on all aspects and elevations. Dry loose surface avalanches may occur from steeper terrain features.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–3
    Weak layers buried near the base of the snowpack can't be dismissed while new snow or rain load the surface. I'd limit my exposure to large overhead slopes, especially when the sun makes an appearance on Monday.

Weather Forecast

Friday: Cloudy with possible sunny periods. Alpine temperatures near -2 and freezing levels 700 m. Ridgetop winds strong from southwest. Saturday: Snow amounts 20-40 cm with the heavier accumulations in the northern part of the region. Alpine temperatures -2 and freezing levels 800 m. Moderate to strong ridgetop winds from the southwest. Sunday: Snow amount 5-10 cm. Alpine temperatures near -3 and freezing levels 600 m. Check out the Mountain Weather Forecast for more detail.

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Friday

Avalanche Summary

On Thursday, numerous loose wet avalanches size 1-2 were reported from below treeline elevations. Avalanche activity will likely increase through the forecast period with new rain, snow and wind.I'd also remain suspect of the deep persistent layers. On December 7th and 8th a few deep persistent slabs to size 3 out of steep south facing alpine terrain in the Skeena corridor west of Terrace were reported. Basal facets were thought to be the culprit in these events. The deep persistent slab is something to keep on your radar, especially with additional stress of the new storm snow.

Snowpack Summary

On Thursday the region received another 10-20 mm of rain at most elevations and some new snow at high alpine elevations. With freezing levels dropping the remainder of the precipitation may fall as snow during the forecast period and likely have a poor bond to the old snow surfaces. The alpine and treeline has seen significant wind effect on all aspects including wind slab and wind pressed snow. Below the surface sits a well-settled snowpack overlying several layers of interest. Down 70-100 cm you'll likely find a 5-10 cm thick crust which was buried on November 23 and in some areas, a feathery surface hoar layer down 50-60 cm producing moderate snowpack test results. The widespread crust/facet interface that was buried at the end of October can now be found 100-200 cm deep and exists region wide.

Regions covered