Avalanche forecast

Northwest Coastal

Jan 9, 2017Avalanche Canada
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Avalanche danger

Mon
Tue
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Strong to extreme winds will transport new snow and maintain dangerous avalanche conditions.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3
    Strong winds will continue to build touchy slabs that sit above a variety of weak layers including surface hoar.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–4
    Weak layers of buried surface hoar up to 1.5 metres deep may be reactive after the recent loading. Take extra care to avoid thin trigger points and exposure to overhead hazard.

Confidence

Low - Wind effect is extremely variable

Weather Forecast

The main story is the strong to extreme easterly winds forecast Sunday into Monday. Little precipitation is expected during the forecast period with below average temperatures. SUNDAY: Cloudy, moderate east winds becoming strong to extreme overnight, alpine temperatures around -12. MONDAY: Trace to 5cms snow possible in the morning. Clearing in the afternoon, moderate to strong outflow (east) winds, alpine temperatures around -12.TUESDAY: Sunny, strong outflow (east) winds, alpine temperatures around -15.WEDNESDAY: Sunny, strong outflow (north) east winds, alpine temperatures around -15.

Avalanche Summary

A widespread cycle was reported following the latest storm, mostly Size 2 wind and storm slabs. All elevations were represented: alpine to steep open areas below treeline. (Deep) persistent natural slab avalanches continue to rear their ugly heads, the last one being in the Ningunsaw area on Thursday. This indicates the persistent problem will linger for some time in the northern part of the region. No recent avalanches have been reported in the southern part of the region.On Monday, the primary concern is fresh wind slabs with the recent snow, although triggering deeper persistent layers remains possible.

Snowpack Summary

20-40 cm of storm snow sits above a variable interface composed of hard wind slabs, weak surface hoar, and faceted snow. Expect this snow to bond poorly to this interface and form extra touchy wind slabs on wind-loaded features. Below the new snow, a well settled slab sits above the Christmas surface hoar layer, which is now buried 40-80 cm deep and may still be reactive in sheltered areas. Deeper weak layers have only been reactive in areas with thin snowpacks. This includes a facet layer from early December that has been reactive in snowpack tests at lower elevations in the southern part of the region, and weak facets near the ground that have produced avalanches in the northern part of the region.

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