Avalanche forecast

Sea To Sky

Apr 22 – 23, 2017Avalanche Canada
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Avalanche danger

Mon
Tue
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Winter hasn't fully loosened its grip at higher elevations. Conditions remain dynamic as yet another storm rolls through the region.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2
    Fresh wind slabs will form over Saturday night as another storm rolls through bringing light snowfall with moderate to strong southwest winds. Slab thickness and reactivity is likely to increase with elevation.

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3
    Where cornices exist, they have become unstable should be avoided. Cornices will gain fragile new growth with Saturday night's snowfall.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2
    Moist new snow at lower elevations will have the tendency to sluff from steep slopes as daytime temperatures rise on Sunday. This may occur naturally or with a human trigger.

Confidence

Moderate -

Weather Forecast

Saturday night: Flurries bringing up to 10 cm of new snow. Moderate to strong southwest winds.Sunday: Cloudy with continuing flurries bringing a trace to 5 cm of new snow . Light south winds. Freezing level to 1600 metres with alpine temperatures of -3.Monday: A mix of sun and cloud with isolated flurries and a trace of new snow. Light east winds. Freezing level to 1800 metres with alpine temperatures of -2.Tuesday: Cloudy with flurries bringing approximately 5 cm of new snow. Light to moderate south winds. Freezing level to 1700 metres with alpine temperatures of -3.

Avalanche Summary

Reports from Friday showed significant cornice activity in the Whistler area, with several natural Size 2 releases and one Size 3.5 that triggered a large slab avalanche with a roughly 2 metre deep crown fracture. One of the Size 2 releases also triggered a 100 cm deep slab. Other natural and explosives triggered cornices ranged from Size 2-3 and mainly entrained loose snow, but a few thinner slabs were also triggered.Reports from Thursday included observations of several explosives controlled cornice releases in the Whistler area. Sizes ranged from 1.5 to 2.5 and one release successfully triggered a 15-30 cm by 15 m slab below it. Wednesday's reports showed explosives triggered storm slabs reaching Size 1.5 in the Whistler area. Crown depths averaged 20 cm.

Snowpack Summary

Light snowfall will combine with moderate to strong southerly winds to form fresh wind slabs on the surface at higher elevations over Saturday night. Below the new snow, warm temperatures and sunshine recently moistened surface snow on most aspects and elevations. New snow will form a variable bond with this surface, with a weaker bond expected at higher elevations and northerly aspects where a crust may have formed in advance of new snow accumulations. The mid and lower snowpack are generally well settled and strong, however large cornice releases have recently demonstrated a capacity for triggering large slab avalanches on underlying slopes.

Regions covered