Avalanche forecast

Sea To Sky

Apr 22 – 23, 2018Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Warming and solar radiation will drive the avalanche danger in the coming days. Watch for conditions that change throughout the day, and be cautious of overhead hazards.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2
    New snow and strong winds from Friday night have formed new wind slabs in upper elevation lee terrain. Although they're likely to gain strength quickly, I'd remain cautious around ridge crests and in gullies.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3.5
    Professionals are traveling cautiously in shaded upper treeline and alpine terrain due to a weak layer buried 60 to 140 cm below the surface. Forecast warming and cornice failures will likely re-activate this destructive interface in isolated terrain

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–2
    Warming and solar radiation are expected to trigger loose wet avalanches, especially in steep, sun-exposed terrain. Loose wet avalanches can be pushy and entrain mass quickly. Warming may also trigger destructive cornice failures.

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

A ridge of high pressure will develop for the forecast period bringing sunny skies and light ridgetop winds. The freezing level will hover around 2800m on Monday and then rise to about 3500m for Tuesday and Wednesday.

Avalanche Summary

On Saturday explosives control produced numerous wind slab avalanches mainly in the size 1.5 range in lee alpine and treeline terrain. Loose wet avalanches and cornice falls are expected to become problematic with warming and solar radiation forecast for this week. Warming also has the potential to wake-up the late March crust interface with the possibility of surprisingly large and destructive avalanches.

Snowpack Summary

New snow and wind on Saturday formed fresh wind slabs in upper elevation lee terrain. The new snow overlies settled storm snow on shaded aspects above 2000m and a melt-freeze crust in most other areas.A weak layer consisting of surface hoar, facets, and/or a melt-freeze crust from late March is now buried about 60 to 140 cm below the surface. This layer is spotty in its distribution and has recently produced large and destructive avalanches. It is most likely to be problematic on west, north, and east aspects between 1900 m and 2250 m. I'd continue to treat this layer very cautiously and would anticipate increase reactivity at this interface with warming forecast for the next few days.The mid and lower snowpack are well-settled and strong.

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