Avalanche forecast

Northwest Coastal

Dec 15 – 16, 2011Avalanche Canada
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Avalanche danger

Sat
Sun
Alpine
4 · High
Treeline
4 · High
Below
4 · High
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Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1–4
    Expect new wind slabs on north through east aspects. Loading may occur lower on the slopes due to forecast high winds in some parts of the region. There's a lot of snow available for transport.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1–4
    Storm slabs will continue to form with forecast snow. Pay attention to the snowfall amounts in your local area, they may vary through the region. More snow = thicker slabs. They can run far, fast and be destructive.

Confidence

Good - -1

Weather Forecast

Friday: Precipitation will be moderate-heavy with snow amounts 30-50cm, and rain at lower elevations. Freezing levels are expected to rise to 1600m in the southern part of the region (Stewart and south). Ridgetop winds will be blowing strong from the south then switching south west. Saturday: Same story. Moderate - heavy precipitation, rising freezing levels during the day, then falling back to valley bottom at night. Sunday: Looks like a break in the systems. Sunny skies, freezing levels at valley bottom and some vitamin D before Monday's weather rolls in.

Avalanche Summary

Control work with explosives has produced numerous avalanches up to size 3 on east-south facing slopes. On Wednesday widespread natural avalanches up to size 2 were reported. These avalanches all ran on the December 09/12 (111209, 111212) buried surfaces ( surface hoar, melt-freeze crusts). With more wind, snow and rising freezing levels Friday/Saturday we can expect another natural avalanche cycle.

Snowpack Summary

The southern part of the region has received up to 50cm of new snow (Kasiks, Terrace areas) and less snowfall to the north. This is forming storm slabs at all elevations. This new snow is being blown around by strong southwest winds creating new wind slabs on lee slopes. Buried beneath the new snow sits a variety of weak snow surfaces (surface hoar, melt-freeze crusts, and facetted snow). This crust is up to 20cm in thickness and extends up to alpine elevations in the south, and around 1000m in the north. The surface hoar growing on the crust was sized up to 10mm. A strong temperature gradient in the top 30cm was reported to be faceting snow below the surface crust. These layers have met their threshold and widespread avalanche activity has occurred. Here's hopes that this surface hoar will get cleaned out in most places. The crust may stick around and create a new sliding surface for Fridays snowfall. If freezing levels do rise to 1700m on Friday we may see rain and new crust formation Saturday when the temperatures drop back down the the valley.The mid and lower snowpack are well settled and strong.

Regions covered