Lawinenlagebericht

Kootenay Boundary

Jan 28 – 29, 2015Avalanche Canada
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Lawinengefahr

Fri
Sat
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

Spring conditions with overnight freezing and daytime warming.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible - Likely
    Größe
    2–4
    Continued warming from high freezing levels and strong solar radiation may result in natural avalanches releasing on the buried persistent weak layer on Southerly aspects. Avalanches may be human triggered on all aspects.

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–4
    Moist or wet loose snow is expected to continue to release from light additional loads, or from strong solar radiation on Southerly aspects. 

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely - Possible
    Größe
    3–5
    Very warm temperatures and high freezing levels may result in deeply buried weak layers reacting to large loads like cornice falls or from light loads in thin snowpack areas.

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Thursday

Weather Forecast

The freezing level should drop to valley bottoms overnight, and then rise back up to about 1500 metres during the day. Expect continued sunny skies and light winds during the day on Thursday. We should see another good re-freeze to valley bottoms overnight and into Friday morning as the cooling continues. More sun and light winds on Friday. Saturday should be cooler with cloud and moderate Southwest winds developing in the morning, and light precipitation starting overnight.

Avalanche Summary

There are no new reports of avalanches. On Monday there were several size 2.0-2.5 loose wet and wet slab avalanches released with explosives at Kootenay Pass, and a size 3.0 natural avalanche in the backcountry near Whitewater ski resort on a Southeast aspect with a very wide propagation that probably released on the mid-January persistent weak layer during a period of strong solar radiation. Moist or wet loose snow avalanches have been reported from several areas up to size 2.0 over the past few days during the warming event. On Saturday a skier triggered a size 2 persistent slab which failed on the mid-December layer. This was a surprising result because it was on a well-supported, concave terrain feature (which had also been heavily skied).

Snowpack Summary

The cool down has started. Overnight freezing down to valley bottoms has created melt-freeze crusts. Strong solar radiation and warm temperatures are affecting the surface layers and turning them moist or wet. We are in a spring like diurnal freeze/thaw cycle. Periods of warming has increased the likelihood of triggering the persistent weak layer of mid-Jan surface hoar layer which is down about 20-60 cm. These large, well-preserved surface hoar crystals sit on a thin crust up to about 1900m on north aspects and all the way to ridgeline on south aspects. A deeper crust/surface hoar combo buried in mid-December is typically down 80-120cm and has produced some large avalanches recently.

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