Avalanche forecast

Purcells

Mar 28 – 29, 2016Avalanche Canada
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Archived · expired 11 years ago

Avalanche danger

Wed
Thu
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Expect avalanche danger to rise during the day, particularly on sun-exposed slopes. Plan to start your day early and move away from large sun-drenched slopes during the heat of the day.

Avalanche problems

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    3–6
    Tread cautiously near large overhanging cornices. Weak cornices could pop off naturally, potentially triggering large slabs on the underlying slope.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3–6
    Intense spring sun and rising temperatures could reactivate buried persistent weaknesses in the upper snowpack.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2
    Expect loose wet slides on steep sunny slopes in the afternoon. A wet sluff in motion could trigger deeper weaknesses creating large destructive slabs.

Avalanche Summary

There was one report of a size 2 natural cornice fall on Sunday that did not trigger a slab below. No new slab avalanches were reported on Saturday or Sunday. Explosives control on Friday produced a few size 2-2.5 cornice releases, but none of these triggered slabs below. There was one report of a natural cornice fall on Friday that did trigger a size 2.5 slab, releasing at or near the ground in places.

Confidence

Moderate

Weather Forecast

WEATHER SUMMARY: It will be a sunny and warm week! Temperatures will steadily climb each day with the freezing level reaching at least 2500 m by Thursday (treeline temps near +5). Ridge winds should be generally light from the NW-NE.

Snowpack Summary

Thin new wind slabs have formed in exposed lee terrain in the alpine and at treeline. Southerly aspects should go through a daily melt-freeze cycle throughout the week. Buried persistent weak layers continue to be a concern for remote triggering in isolated areas where crusts are not strong enough to "bridge" the weakness. The late February surface hoar/crust layer is down 40-90 cm. This layer may continue to react to human triggers during periods of strong solar radiation and high daytime temperatures. Loose wet avalanches in motion, or cornice falls may step down to deeply buried weak layers. Cornices continue to be described as large and fragile, and may fail with forecast warming and strong sunshine this week. Conservative terrain without overhead hazard is a good strategy for avoiding the persistent slab problem.

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