Avalanche forecast

Northwest Inland

Jan 3, 2017Avalanche Canada
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Avalanche danger

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

Expect change to be slow. Wind slabs will be slow to bond, and deep persistent weak layers will continue to be a concern for large avalanches.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2
    Extreme winds will continue to redistribute loose surface snow into reactive wind slabs. Watch for areas that were previously scoured and may become reverse-loaded by northerly winds.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    2–3
    40-60 cm of recent snow sits above a weak, faceted lower snowpack. This fundamentally weak snowpack structure supports human-triggered avalanches from places like convex slopes in shallow areas, and is likely to persist for some time.

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

Some thin high cloud overnight with strong northeast winds. Cold and clear on Tuesday with temperatures 5-10 degrees warmer in the alpine than in the valleys. Cold and clear on Wednesday with light-moderate northerly winds, some chance of a weak above freezing layer in the alpine. Cloud developing on Thursday with moderate westerly winds and no new precipitation.

Avalanche Summary

In the north of the region near Ningunsaw there was a natural avalanche size 3.5 that released in the basal facets on Monday. This is a good reminder that large full depth avalanches are possible in shallow snowpack areas. A natural avalanche cycle with slides up to size 2 occurred Friday in the mountains near Smithers. This was in response to the strong northerly winds. Wind slabs will likely remain touchy throughout the forecast period, as sustained winds redistribute any loose surface snow. Deeper persistent weak layers will also remain a concern, it is possible to trigger large avalanches.

Snowpack Summary

Snowpack depths in this region are still shallow - around 1 m or so, meaning there are a lot of weak sugary facets in the snowpack. Recent storm snow is being redistributed by strong to extreme winds, and wind slabs are widespread behind exposed features. Where hard wind slabs overlie weak facets, the structure is ripe for human-triggered avalanches.In addition to the sugary facets, you may find a layer of feathery surface hoar (up to 15 mm in sheltered areas), buried around 20 - 30 cm below the surface. There is another weak layer that formed during the early December cold snap which is now about 40-60 cm deep. A crust from mid-November may be found close to the bottom of the snowpack nestled in amongst the facets. We don't have a lot of information about these layers, but it's worth noting the layer responsible for most of the large avalanches during the big storm just before Christmas was the mid-November rain crust.

Regions covered