Bulletin d’avalanche

Northwest Coastal

Dec 18, 2017Avalanche Canada
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Archivé · expiré 9 years ago

Danger d’avalanche

Tue
Wed
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Points saillants

We are not sure how the snowpack is reacting to the 20 to 60cm of snow that fell over the weekend. Tread cautiously out there as you continue to gather information about the storm, wind and deep slabs that exist in our early winter snowpack.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–3
    20 to 60cm of snow fell during the weekend with wind from the SW, W, NW and even SE. This snow is likely settling into a cohesive slab that rests on a variety of old surfaces, including a prominent crust.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    2–4
    A significant new load has been added to the snowpack and the chance of triggering a deep persistent slab has likely increased. Scale the objectives back a bit as we all continue to gather information about this slab.

Confidence

Moderate - Wind speed and direction is uncertain on Wednesday

Weather Forecast

The Northwest Coast is expected to be relatively cool and dry for the forecast period as a more zonal pattern favors the regions along the 49th parallel. Dribs and drabs of snow are possible on Monday before yet another ridge takes over for the foreseeable future.MONDAY: Broken cloud cover, freezing level around 500m, moderate west/southwest wind, 1 to 5cm of snow. TUESDAY: Sky clearing through the day, freezing level at valley bottom, light variable wind, no new snow expected.WEDNESDAY: A few clouds, freezing level around 400m, strong to extreme northwest wind, no new snow expected.

Avalanche Summary

On Saturday several size 1 to 1.5 wind slabs were observed in steep terrain. Poor visibility likely limited observations, it is expected that a natural avalanche cycle occurred during the storm.

Snowpack Summary

The region picked up 20 to 60cm of storm snow over the weekend accompanied by winds out of the southwest, west, northwest, and even a bit of southeast. This has likely led to the development of a cohesive slab, especially in wind exposed features. These new storm and wind slabs rest on a rain saturated snowpack between valley bottom and 800m. Above 800m, the new storm snow rests on settled old snow, or a melt freeze crust that is 3 to 15cm thick. Below this crust the mid-pack is strong, but there are reports of a feathery surface hoar layer down 50 to 60cm in sheltered locations. There is a second prominent crust that is associated with facets that was buried at the end of October, look for this widespread interface down around 100 to 200cm below the surface.

Régions couvertes