Avalanche forecast

South Rockies

Feb 12 – 13, 2015Avalanche Canada
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Avalanche danger

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

Warm temperatures and sunny breaks are on the menu for Friday. Use caution in steep open terrain and around large overhanging cornices.

Avalanche problems

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–4
    Warm temperatures could make large cornices unstable. Not only are they a hazard in themselves, but they could also act as a heavy trigger for large slab avalanches on the slope below.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–4
    Warm temperatures and sunny breaks on Friday could destabilize the recent snow resulting in natural slab or loose wet activity in steep terrain.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    3–5
    A deeply buried week layer which formed in December should still be treated with suspicion. Not much is known about the current reactivity of this potentially destructive layer, but I'd use extra caution in steep, unsupported alpine terrain.

Confidence

Fair - Due to the number of field observations

Weather Forecast

Friday: Cloudy with sunny breaks. The freezing level is between 2500-3000 m. Ridge winds are light to moderate from the west. Saturday: Cloudy with possible light snow. The freezing level lowers to around 1500 m. Winds are generally light from the W-NW. Sunday: Mainly cloudy with light snow. The freezing level is around 1200-1500 m.

Avalanche Summary

Observations have been essentially non-existent in recent days. This likely speaks more to a lack of observers rather than actual conditions. I'm confident recent storm loading has produced large storm slab avalanches at higher elevations, while loose wet or wet slab avalanche activity occurred at lower elevations where rain fell.

Snowpack Summary

The rain line during recent heavy precipitation generally hovered around 1700m, although there were periods where rain fell into the alpine. Above that elevation, heavy accumulations of moist, dense snow have been pushed by strong southwest winds into much deeper deposits on the lee side of ridgecrests and terrain breaks. This recent storm snow overlies a hard crust, which may have overlying surface hoar that was buried late January. The mid-December crust/facet/surface hoar weakness may be persisting in the mid to lower snowpack at higher elevations.

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