Avalanche forecast

Kootenay Boundary

Mar 20 – 21, 2019Avalanche Canada
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Avalanche danger

Fri
Sat
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

Persistent hot and sunny weather is driving the avalanche danger. Avoid avalanche terrain especially in the afternoon on sunny slopes when the danger is at its HIGHEST.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1.5–3
    Warm temperatures are penetrating deeper into the snowpack and a cohesive slab now sits above a series of weak layers. Large slab avalanches are failing on sunny slopes with warming.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–2
    Loose wet activity is expected to continue on most aspects and elevations. Cornices are softening up and becoming weak. You don't want to be under or near one of these looming monsters when they fail.

Avalanche Summary

On Tuesday, a widespread natural loose wet and wet slab avalanche cycle occurred up to size 2.5. These avalanches were from sunny aspects (SE-SW) 1700-2000 m. Explosive controlled wet slab avalanches up to size 3 were also triggered on sunny aspects between 1900-2200 m. Continued warming and a lack of overnight re-freeze we expect to see natural avalanche activity to continue.

Confidence

Moderate -

Weather Forecast

THURSDAY: A mix of sun and cloud. Freezing levels 3200 m and alpine temperatures near +9 degrees. Ridgetop winds light from the southeast.FRIDAY: A mix of sun and cloud. Freezing levels 2900 m and alpine temperatures near +8 degrees. Ridgetop winds light from the southeast.SATURDAY: Cloudy with light precipitation falling as rain at treeline and below and snow in the alpine. Freezing levels 1800 m and alpine temperatures falling to +1 degree. Ridgetop winds light from the South.

Snowpack Summary

Currently, solar aspects are showing signs of melt by day and a freeze by night. In some locations, sheltered northerly aspects have new surface hoar forming and variable wind effect remains on exposed slopes at treeline and in the alpine. The current snowpack is complex and with the continued warming and little overnight re-freeze the snowpack will continue to break down. The bigger questions are deeper in the snowpack. Two crusts exist in the upper snowpack and the bond of the overlying snow is most concerning with deteriorating. The first crust is down 20 to 30 cm and loose wet avalanches have slid on this interface. The deeper one down 60-95 cm has also been producing easy shears in test profiles and potentially just waiting for enough heat to penetrate and deteriorate before avalanches start failing on it, if they do? Its hard to say how many hot days and warm nights it will it take to wake up the more deeply buried weak layers.

Regions covered