Avalanche forecast

Northwest Coastal

Dec 19, 2017Avalanche Canada
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Archived · expired 9 years ago

Avalanche danger

Wed
Thu
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Cool and stable weather should mean a gradually strengthening snowpack.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    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

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–3
    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 - Due to the number of field observations

Weather Forecast

The storm track will follow the Canada -- USA border over the next few days so the Northwest should be cool and dry.Tuesday:  Mix of sun and cloud, dry, light to moderate northeast winds, and alpine temperatures around -5 C.Wednesday:  A temperature inversion could mean sunshine in the alpine but grey and cold below the valley cloud. Nil precipitation. Alpine temperatures could near freezing; colder at low elevations. Light but gusting northwest wind. Thursday:  Mix of sun & clouds. Dry. Light but gusting north wind. Alpine temperatures around -5 to -10 C.

Avalanche Summary

The north part of the region reported up to size three natural avalanches over the weekend. Poor visibility limited observations in the south but no new avalanches were reported.

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 on or right around this crust in sheltered locations. There is a second prominent crust that is associated with facets buried at the end of October, look for this widespread interface down around 100 to 200cm below the surface.

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