Avalanche forecast

Northwest Coastal

Feb 23 – 24, 2012Avalanche Canada
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Archived · expired 15 years ago

Avalanche danger

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

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–5
    Moderate to strong winds and new snowfall will create new and reactive wind slabs on lee terrain. Expect wind slab development to occur throughout the forecast period. The winds are a changin' and blowing from the SE. Suspect reverse loading.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–5
    This new snow may create touchy storm slabs that sit on a variety of buried weak layers. The slab that sits on these layers is up to 40cm thick, and growing.

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

An approaching low pressure system will bring light-moderate precipitation to the NW regions Thursday night through to Saturday. Friday: Snow amounts 10-20cm through the day. Ridgetop winds 30km/hr from the SE. Treeline temperatures near -7. Freezing levels 200m. Saturday: Light snowfall amounts. Ridgetop winds light-moderate from the SE. Freezing levels remain at valley bottom. Sunday: A ridge of high pressure will bring dryer, cold conditions.

Avalanche Summary

Reports across the region of widespread size 1-2 natural avalanche activity. Majority of aspects being NE-N. Many of these are reported as wind slabs releasing on buried crusts that formed mid February. In the Eastern area of the region a size 2.5 natural avalanche occurred on February 21st. This occurred on an East aspect @1700m, running 900m in length. Wind slab activity up to size 2 on Southerly aspects have also been reported. On February 20th a natural size 2.5-3 was reported from Mt. Rainy. With forecast wind and snow for Friday, I suspect avalanche activity to increase.

Snowpack Summary

Generally, up to 35 cm of new snow sits over a strong melt freeze crust that exists below 1000m on all aspects, and over wind-pressed powder on shaded alpine features. Facets and spotty surface hoar have been found sandwiched between the newer snow and the old surfaces at treeline and below. This surface hoar seems to be more predominant in inland areas. Where it exists, this layer has started to become reactive under the new load and slab development. I suspect this will continue as the forecast snow and wind continues. The mid and lower snowpack is generally well settled and strong. Check out our Forecaster's Blog for some insight on incremental loading. A Special Avalanche Warning has been issued for the North Coast Inland, and Interior regions of BC. Some of these problems may exist in the eastern parts of your region, but reports suggest it's not a widespread problem. Keep yourself informed and up to date by reading the current avalanche bulletins, the special warning, and be aware of the snowpack conditions in your "local" mountains.

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