Avalanche forecast

Sea To Sky

Dec 21 – 22, 2017Avalanche Canada
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Avalanche danger

Sat
Sun
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Strong northerly, outflow winds have redistributed the recent storm snow at upper elevations. Watch for areas of wind loaded snow near ridge tops and exposed features.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–3
    Wind affect at upper elevations is highly variable with areas of soft and hard wind slab on leeward slopes slopes. These slabs may be easily triggered by a skier or rider.

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

FRIDAY: Mix of sun and cloud, light flurries. Accumulation trace. Ridge wind light from the northeast. Temperature -8. Freezing level surface.SATURDAY: Mostly sunny. Ridge wind light from northeast becoming east. Temperature -9. Freezing level surface.SUNDAY: Cloudy, flurries. Accumulation 5-10 cm. Ridge wind light from the southeast becoming south. Temperature -8. Freezing level surface.

Avalanche Summary

On Wednesday observers reported evidence of a natural avalanche cycle to size 2 during the storm, as well as several small, skier-triggered and explosives triggered slab avalanches up to Size 3 on wind-loaded slopes in the alpine and at treeline. See here for a recent Mountain Information Network (MIN) report.On Tuesday, numerous natural, skier controlled and skier remote storm slab avalanches to Size 1.5 were reported on various aspects at treeline and below running both within the storm snow as well as on the Dec 15th melt-freeze crust. See here for details. Ski cutting also produced a Size 2 storm slab avalanche in the alpine on Tuesday. And on Monday, we had reports of reactive wind slabs on steep north-facing slopes. See here for the MIN report.

Snowpack Summary

The recent storm snow has been redistributed by strong northerly winds building wind slabs on lee aspects and scouring windward aspects in the alpine and exposed treeline areas. This has created a highly variable upper snowpack depending on aspect and elevation with areas of both soft and hard snow as well as areas of exposed crust. An average of 30-50cm of storm snow now sits on a melt-freeze crust (December 15th layer) that formed on all aspects and elevations. On high north aspects this crust is thin with dry, sugary snow crystals (facets) below. Below the upper December 15th crust, the late November crust is now buried 70-100 cm with a thin layer of facets above. Beneath this crust the lower snowpack is well settled.

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