Avalanche forecast

South Rockies

Apr 4 – 5, 2014Avalanche Canada
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Avalanche danger

Sun
Mon
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

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Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–3
    Forecast Westerly winds may continue to transport snow into pockets of wind slab on lee slopes. Weak cornices may continue to develop new growth that may be easy to trigger.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    3–6
    Avalanches releasing on the deeply buried weak layer from early February are still a concern. Strong solar radiation, cornice falls, new loading, or storm slab avalanches in motion are all possible triggers.

Confidence

Fair - Freezing levels are uncertain

Weather Forecast

Overnight and Saturday: Moderate Westerly winds overnight and freezing levels dropping down to 1500 metres. Strong Southwest winds developing in the afternoon as the freezing level rises up to 2000 metres.Sunday: Freezing levels remaining near 2000 metres. Some light precipitation overnight ending as winds shift to the Northwest.Monday: Freezing levels climb to 3000 metres as warm air moves into the region. Chance of broken skies and periods of strong solar radiation. Winds light to moderate from the Southwest.

Avalanche Summary

Some very large avalanches up to size 3.0 were reported from the Harvey pass area. These natural avalanches may have been a couple of days old, and it is suspected that they either ran on or stepped down to the February deep persistent weak layer. Avalanches releasing on this layer may become more likely during the forecast very warm weather early next week.

Snowpack Summary

Solar radiation and high freezing levels have created new melt-freeze crusts on Southerly aspects. The 20-40cm of recent new snow sits on top of a thick sun crust on solar aspects. 70-90 cm of settling storm snow from the past week rests on a graupel layer that can be found in much of the region. This makes for around 90 cm on top of the mid march crust at this point. This crust exists on all aspects below 2000m and on solar aspects in the high alpine. North of Sparwood and in the Crowsnest Pass area, the buried crust seems more specific to previously sun-exposed slopes. The deep facet/crust persistent weakness buried at the beginning of February (now down 140 to 170cm) seems unlikely to trigger in areas where the hard, supportive crust exists. No matter where you are in the region, this weakness should stay on your radar as any activity at this interface would be large and destructive. Possible triggers include a large cornice fall, a large input in a thin snowpack area or solar warming.

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