Avalanche forecast

Northwest Coastal

Mar 8 – 9, 2016Avalanche Canada
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Avalanche danger

Thu
Fri
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

The heaviest snowfall for the next few days is forecast for the extreme southwest corner of the region. Local avalanche danger could be higher in areas west of Terrace and south of highway 16. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–4
    This ongoing windy and stormy period has led to widespread hard and soft wind slab development in lee and cross-loaded terrain. The wind direction has been variable, meaning all aspects are suspect.

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–4
    Cornices are very large and could fail with continued growth and/or warming.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–4
    Weaknesses may exist within or at the base of the recent storm snow. In some areas up to 60 cm of fresh snow sits on a weak surface hoar layer. Look for this in sheltered terrain near treeline. 

Confidence

Moderate

Weather Forecast

WEDNESDAY: Cloudy with light to moderate snow – 5-15 cm. The freezing level gradually climbs to 1200-1400 m near the end of the day. Ridge winds are light increasing to strong from the E-SE. THURSDAY: Periods of snow – 10-20 cm. The freezing level dips back to 800-1000 m by the end of the day and winds are moderate from the S-SE. FRIDAY: Cloudy with sunny breaks. The freezing level is around 1400 m and winds are light.

Avalanche Summary

Observations on Monday were limited due to poor visibility; however, there were a few reports of natural slab avalanches up to size 2 from immediate lee slopes in the alpine. There was also a report of a size 3 avalanche that initiated on a north aspect in the alpine, and a large natural cornice fall. Expect wind slabs to remain sensitive to rider triggering in steep exposed terrain.

Snowpack Summary

Over the past few days we've seen snowfall accumulations of 5-15 cm each day, and storm snow totals of around 40-60 cm. Strong to extreme ridgetop winds have shifted the new snow into hard or soft wind slabs at treeline and in the alpine, adding to an ongoing wind slab problem. Some areas are reporting a weak surface hoar layer near the base of the most recent storm snow. An old crust buried in early February can now be found around 80-120 cm below the surface. This crust, which may coexist with small facets or decomposing surface hoar, recently produced sudden planar ("pops") results in snowpack tests. Although no recent avalanches were reported to have failed at this interface, I'd remain suspicious of this layer in steep, unsupported terrain at treeline and in the alpine.

Regions covered