Avalanche forecast

South Rockies

Mar 18 – 19, 2015Avalanche Canada
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Avalanche danger

Fri
Sat
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Lingering storm slabs remain a concern, especially in the alpine. Avoid steep unsupported slopes and convexities. Use extra caution on sun-exposed slopes during the heat of the afternoon.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–4
    30-40cm thick storm slabs sit over a new rain crust. At lower elevations or on sunny slopes these slabs may be moist or wet. The slabs are expected to be most reactive at higher elevations, especially on steep, unsupported terrain features.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–3
    Solar radiation and daytime warming will likely deteriorate the upper snowpack, initiating loose wet avalanches. Overhead hazards like cornices could also fail and trigger slab avalanches from the slopes below.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    3–6
    A crust/facet layer down 90-150cm still has the potential to produce very large avalanches with a heavy trigger like a cornice failure or a smaller avalanche in motion stepping down.

Confidence

Fair

Weather Forecast

Thursday should be a mix of sun and cloud. Freezing levels are forecast to peak around 2000m and alpine winds are expected to increase to strong from the SW to W. Friday should be similar with a mix of cloud and sun, and moderate to strong alpine winds from the SW. Freezing levels are expected to climb as high 2500m on Friday afternoon. Light precipitation is possible on Saturday and freezing levels are forecast to drop back to around 2000m.

Avalanche Summary

A widespread natural avalanche cycle to size 2.5 occurred on Monday during the storm. These were primarily storm slab avalanches but several stepped down to deeper persistent weak layers or to the ground in steep unskiable terrain. At lower elevations, loose wet avalanches up to size 2.5 were reported as well as isolated wet slabs. Natural activity quickly tapered off following the storm but the storm slab is expected to still be reactive to human-triggering. It is best to avoid steep unsupported slopes and convexities, as well as steep gully features. There is also concern for avalanches to step down to deeper persistent weak layers in isolated areas. Loose wet avalanches are a concern on sun-exposed slopes during the heat of the afternoon.

Snowpack Summary

The recent storm snow is settling into a cohesive slab which is typically 30-40cm thick. Up to at least 2000m elevation, the snowpack below the new storm snow is moist or wet from the warming and heavy rain last week. A weak rain crust sits between the storm snow and the lower snowpack. The thick mid-February crust has broken down and is no longer supportive. There are a couple older persistent weak layers in the midpack that are probably breaking down but will remain an isolated concern while the snowpack remains warm.

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