Lawinenlagebericht

Kootenay Boundary

Mar 6 – 7, 2016Avalanche Canada
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Lawinengefahr

Tue
Wed
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

Storm slabs continue to be a concern. Wide fracture propagations are possible where the storm snow is sitting on a weak buried layer of surface hoar.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    3–6
    The deeply buried persistent weak layer of surface hoar may be less likely to trigger after the warm storm and subsequent cooling trend. Avoid un-supported slopes and shallow wind effected terrain adjacent to large alpine features.

  • Storm Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–4
    Storm slab avalanche may continue to be triggered by light additional loads at higher elevations where there was more snow than rain in the last storm.

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible - Likely
    Größe
    1–4
    Loose wet avalanches may continue to be triggered below treeline if the freezing level does not drop overnight. Watch for strong solar radiation if the sun shines on Monday.

Confidence

Moderate - Freezing levels are uncertain on Monday

Weather Forecast

Freezing level dropping down close to valley bottoms overnight with continued light precipitation. Light precipitation and cloudy skies on Monday combined with moderate southerly winds and freezing levels climbing up to about 1700 metres. A spring diurnal freeze/thaw cycle setting up for Tuesday and Wednesday with freezing levels dropping to valley bottoms overnight and then rising up to 1500 metres during the day. The next major storm pulse developing on Wednesday night.

Avalanche Summary

Loose wet avalanches and moist storm snow avalanches were reported on Sunday. Natural avalanches were reported up to size 2.5 on Saturday. Skier accidental, remotely triggered slab avalanches, and natural avalanches up to size 2.0 were reported on Friday. Explosives also released cornices up to size 3.0. On Thursday, a size 1.5 storm slab was ski cut on a northwest aspects at 2050m. This slab failed on the late-February surface hoar layer down 30-50cm. Numerous small ski cut avalanche were also reported to be failing on this layer through the region.

Snowpack Summary

Forecast rain and high freezing levels may rapidly increase the likelihood of triggering storm slabs and persistent weak layers. New snow and wind has added to the 30-50cm of recent storm snow that overlies a layer of well-developed surface hoar (up to size 20mm) which is very reactive to human triggers. This layer is widespread above 1700m except on south aspects where the interface was cooked by the sun and now exists as a buried sun crust. Significant wind transport has been noted so expect to find deeper, more destructive slabs in exposed lee terrain. 80-100cm below the surface you will likely find the mid-February crust/facet/surface hoar layer. Although this layer has become less likely to trigger, avalanches failing at this interface could be large and destructive.

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