Avalanche forecast

South Rockies

Feb 7 – 8, 2015Avalanche Canada
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Avalanche danger

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

The storm may have tapered-off, but the snowpack will need time to adjust to the heavy load of the new snow, and water saturation at lower elevations. Conservative terrain selection remains critical.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–4
    Deep, dense and destructive storm slabs have formed at upper elevations. Human triggering will remain a concern, especially due to a recently buried crust/ surface hoar layer.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3
    Heavy rain and forecast warm temperatures will promote ongoing loose wet avalanche activity. Loose wet avalanches can be pushy and entrain mass quickly. Use extra caution in steep gullies.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–5
    The snowpack is rain-soaked and weak. This increases the likelihood of avalanches failing on deeply buried persistent weak crystals which formed in December. Although less likely, avalanches at this interface would be destructive in nature.

Confidence

Fair - Due to the number of field observations

Weather Forecast

The pineapple express will persist for Sunday and Monday, but it will lose much of its "punch". A warm, dry ridge will then build for Tuesday. Sunday: Light precipitation / Strong southwest winds / Freezing level at 2000m Monday: 5-10cm of snow at higher elevations / Moderate to strong southwest winds / Freezing level at valley bottom with a chance of an inversion  Monday: A mix of sun and cloud / Light northwest winds / Freezing level at valley bottom with a chance of an inversion

Avalanche Summary

Observations have been extremely limited in recent days. That said, several storm slab avalanches to size 2.5 were reported in the south of the region on Friday. I get the feeling this was just the tip of the iceberg. Triggering storm slabs will remain a concern at higher elevations for the next few days. At lower elevations where precipitation has fallen as rain, I would expect ongoing loose wet and wet slab avalanche activity.

Snowpack Summary

In the alpine, up to 50cm of moist, dense snow overlies a touchy crust/surface hoar layer which was formed in late January. These new snow accumulations have been pushed by strong southwest winds into much deeper deposits in upper elevation lee terrain. At lower elevations very heavy rain has saturated the snowpack. I'm sure cornices are large and fragile.The sustained rain should continue to break down the late January crust, increasing the possibility of avalanches stepping down to deeper weak layers. The mid-December crust/facet/surface hoar combo is found down 50 - 95 cm. Rain and/or heavy storm loading could spark renewed activity at this interface with the potential for very large avalanches.

Regions covered