Avalanche forecast

Northwest Coastal

Mar 1, 2018Avalanche Canada
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Archived · expired 9 years ago

Avalanche danger

Fri
Sat
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

Storm snow and wind continue to overload the snowpack. Strong outflow winds and light snowfall are expected to continue into Thursday. Choose conservative terrain and avoid overhead hazard. Recent large avalanches have run long distances.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    2–4
    Recent storm snow totals of 60 -100 cm, accompanied by on-going strong winds have over-loaded weak layers buried deep in the snowpack, resulting in very large, destructive avalanches.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1.5–3
    Snow and strong wind continue to build fresh storm slabs, which have failed both naturally and with the weight of a person in recent days. Avoid steep or convex terrain, as well as wind-loaded areas on the lee side of ridges and cross-loaded slopes.

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

TONIGHT: Flurries. Accumulation 5-10 cm. Ridge wind strong, east. Temperature near -6. Freezing level 500 m.THURSDAY: Cloudy, flurries. Accumulation up to 5 cm. Ridge wind moderate to strong, east. Temperature near -5. Freezing level 300 m.FRIDAY: Mix of sun and cloud. Ridge wind moderate, east. Temperature near -5. Freezing level valley bottom.SATURDAY: Sunny. Ridge wind light, east. Temperature near -10. Freezing level valley bottom.

Avalanche Summary

On Wednesday and Tuesday we received a reports of two very large (size 4 and 4.5) natural avalanches that are suspected to have failed on a deep weak layer near the base of the snowpack. The larger of these occurred near Snowbound Creek west of Terrace on a south aspect at 1400 m and ran full path from ridge top to valley bottom, destroying a significant amount of mature forest beyond it's historical trimlines. Skier controlled and natural wind slab avalanches up to size 2 were also reported on Tuesday on north to east aspects between 1200-1400 m.Evidence of a widespread natural cycle up to size 3 was reported from Sunday and Monday. And explosive control work on Monday produced numerous size 2.5 - 3 storm slabs on southeast through southwest aspects at all elevations.Skiers in the Shames area on Sunday reported reactive storm slabs up to size 2 on south and west aspects. Read the MIN report here.In the north (colder & drier inland area) near Ningunsaw there was a remotely triggered size 2.5 avalanche on Sunday with a hard slab releasing near the ground in shallow snowpack area with a gentle start zone.

Snowpack Summary

Recent storm snow accumulations of 50-100 cm have been affected by ongoing moderate to strong westerly winds at alpine and treeline elevations. Recent storms are burying older hard wind slabs and scoured surfaces in wind-exposed areas. In wind-sheltered terrain, sun crusts or dry facets sit below the recent storm snow.In the upper pack about 100-150 cm deep, is an interface of sun crusts, facets and spotty surface hoar (which is most prevalent in sheltered treed locations) that was buried mid-February. Deeper in the snowpack, around 150-200 cm down, you'll find a crust/surface hoar layer from January which still has the chance to surprise you and could be triggered from a thin snowpack spot, or with a large trigger like cornice fall. Basal facets may be found near the bottom of the snowpack in colder / drier parts of the region.

Regions covered