Avalanche forecast

South Rockies

Mar 19 – 20, 2015Avalanche Canada
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Avalanche danger

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

Wind slabs may be building at higher elevations where there is still dry snow. Continued warm conditions means loose wet avalanches remain a concern during the heat of the afternoon.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–4
    Strong winds are forming thin new wind slabs or adding to the old slabs in leeward terrain features.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–3
    Solar radiation and daytime warming will weaken the upper snowpack and increase the likelihood of 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

A mix of sun and cloud is expected for Friday with freezing levels reaching around 2500m and moderate-strong SW winds in the alpine. The north end of the region could see light scattered precipitation on Friday. On Saturday, light precipitation is expected and models are currently showing 2-6mm. Freezing levels are forecast to fall to below 1500m by Saturday afternoon. Alpine winds should remain moderate-strong from the SW. A mix of sun and cloud is expected for Sunday with freezing levels 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. On Friday, wind loaded areas are the biggest concern.  New wind slabs will be touchy and may overload older wind slabs in leeward terrain features. Loose wet avalanches are a concern on sun-exposed slopes during the heat of the afternoon or areas that receive rain.

Snowpack Summary

The recent storm snow is settling into a cohesive slab which is typically 30-40cm thick. This snow is now moist or wet on all aspects and elevations except high elevation north facing terrain. Wind affected snow is expected in the high alpine and ongoing winds may be adding additional load to slabs in leeward terrain features. Up to at least treeline 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.

Regions covered