Avalanche forecast

Northwest Coastal

Feb 16, 2018Avalanche Canada
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Archived · expired 9 years ago

Avalanche danger

Sat
Sun
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Large cornices and storm slabs have formed following Tuesday's big storm event. Reactivity of these may increase if the sun starts to pack a punch, especially on solar and leeward aspects.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–3
    Recent heavy snowfall and strong winds have formed widespread storm slabs. At treeline and below these slabs overlie recently buried surface hoar and have been reactive to light triggers.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

TONIGHT: Cloudy, flurries. Accumulation up to 5 cm. Ridge wind moderate, west. Temperature -5. Freezing level 500 m.FRIDAY: Mix of sun and cloud. Ridge wind light, south. Temperature -7. Freezing level 300 m.SATURDAY: Mix of sun and cloud, light flurries. Accumulation trace. Ridge wind moderate to strong, northeast. Temperature -12. Freezing level valley bottom.SUNDAY: Sunny. Ridge wind moderate, northeast. Temperature -12. Freezing level valley bottom.

Avalanche Summary

There were no new reports of avalanches on Thursday.A widespread natural avalanche cycle up to size 3.5 was reported on Wednesday following the intense loading from new snow and wind, with at least one avalanche running beyond it's historical runout distance. Explosive control work on Wednesday produced numerous storm slab releases up to size 2.5, at all elevations. At lower elevations, treeline and below, these slabs were failing on a layer of surface hoar buried by the storm snow on Tuesday.Large cornices have formed as a result of continued moderate, westerly winds and Tuesday's storm event.  Expect these to be weak particularly with daytime warming and sunny weather.

Snowpack Summary

Approximately 40-60 cm of new snow has fallen across the region since Tuesday with the highest snowfall amounts in the Terrace area.This new snow sits on a wide array of surfaces - including wind scoured from strong and variable winds during the long weekend, and fresh wind slabs at higher elevations on lee (downwind) slopes, as well as facets and surface hoar in sheltered locations at treeline and below, and suncrusts on steep solar aspects.Also a 5-20 cm thick crust/surface hoar layer that was buried early February and can be found 60-110 cm below the surface on all aspects up to 1400 m. In thinner snowpack areas (north and inland), a deeper crust / surface hoar layer that was buried in mid-January in sheltered areas at treeline and below could still be a concern for triggering from shallow spots.

Regions covered