Avalanche forecast

South Rockies

Mar 16, 2019Avalanche Canada
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Avalanche danger

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

We're expecting mostly cloudy conditions on Saturday, but slopes receiving direct sun could produce loose wet avalanches surprisingly quick.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–2
    Wind blowing from various direction has formed slabs in unexpected areas. Newly formed slabs may be more reactive than expected with this intense warming and direct sunlight.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    1–2.5
    Although the likelihood of triggering a persistent slab is fairly low, the consequences can be severe as the weak layer is deep in the snowpack.

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

FRIDAY NIGHT: Partly cloudy, alpine low temperature of -5C, moderate westerly winds at ridgetop.SATURDAY: Cloudy with sunny periods, alpine high temperature of -2C, light west wind, freezing level between 1600m and 1800m. SUNDAY: Sunny with cloudy periods, alpine high temperature near 0C, light west wind, freezing level around 2000m, no overnight re-freeze expected.MONDAY: Mainly sunny, alpine high temperature of +3C, light west wind at ridgetop, freezing level around 2500m, no overnight re-freeze expected

Avalanche Summary

Two notable large natural persistent slabs releases were observed on northwest slopes at treeline on Thursday. A few natural avalanches (up to size 1.5), mainly dry-loose and thin wind slabs were also observed on steep slopes. Ridders were surprised to remotely trigger a small persistent slab avalanche down 60 cm late Thursday afternoon on a west facing slope below treeline. See the MIN report from Lizard Range and Flathead for more details. With the upcoming warming natural avalanches are increasingly likely as the sun impacts solar aspects.

Snowpack Summary

Moderate to strong southwest winds have affected the low density storm snow at and above treeline, building winds slabs near ridgetop and behind lee features. These fresh slabs overly old slab slabs in alpine terrain. The sun has transformed the recent 15-20 cm of storm snow which became moist on southerly aspects at lower elevations. The middle snowpack consists of weaker faceted snow with few if any distinct layers. In isolated wind protected locations a thin surface hoar layer from mid-January is 50-80 cm deep. The surface hoar is most prominent in the Elk Valley between 1600 m and 1900 m. Regardless of whether they are facets or surface hoar crystals, when the weather warms they may produce avalanches on steep unsupported slopes.

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