Lawinenlagebericht

Kootenay Boundary

Feb 20 – 21, 2016Avalanche Canada
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Archiviert · abgelaufen 11 years ago

Lawinengefahr

Mon
Tue
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Kernpunkte

Large amounts of recent storm snow may push the danger to higher than forecast. This is a good time to be conservative with route selection.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–3
    New snow combined with moderate to strong south west winds are building wind slabs in lee terrain at tree line and above. New snow may sluff in steep terrain and produce surprisingly large avalanches.

  • Cornices

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–4
    Recent storm snow combined with strong winds have built large and potentially dangerous cornices .  A cornice failure might affect the slope below and trigger a large and destructive avalanche.

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–5
    A buried crust and surface hoar layer lies up to 130cm below the surface in most parts of the region, although it may not be found on every slope, an avalanche at this interface may quite large. Consider this layer for the foreseeable future.

Confidence

Moderate - Due to the number and quality of field observations

Weather Forecast

A ridge of high pressure is building behind the front that passed through yesterday. Fairly dry conditions are expected for tonight.  Another Pacific front will slowly make its way to the South Coast by  mid-day Sunday.  We may see precipitation in the Kootenay Boundary by late Sunday night into Monday morning. Another Pacific front is scheduled to arrive on the coast on Monday morning, but is not expected to produce much precipitation in the southern interior as a ridge of high pressure builds over the whole province.  The interior should remain dry through mid week.

Avalanche Summary

Numerous skier controlled, skier accidental, and naturally triggered storm slab avalanches have been reported in the size1.5,-2 range. These failed in response to heavy storm loading on Wednesday night and Thursday.  A few of these avalanches failed on the February crust interface mentioned in the Snowpack Discussion section. Of note, a size 2 slab avalanche northwest of Kaslo (in the South Columbia region) partially buried 2 people and completely buried another person. The avalanche, which failed on the early February crust interface, occurred on an east aspect at 1700m. Nobody was injured in the avalanche, but it points to the touchy conditions which also extend south into some parts of the Kootenay Boundary region. New snow and wind from Friday night has delivered  another round of wind slab activity. The new storm snow loading will add to the likelihood and consequences of avalanches failing on the buried early February crust.

Snowpack Summary

On Friday, up to 35 cm of new snow fell in the region and now overlies settling storm snow from the past few days. Moderate to strong southwest winds are transporting the new snow into deeper and more reactive wind slabs in exposed lee terrain. 90-120 cm below the surface there is a hard melt-freeze crust which formed during the 2nd week of February. This crust is quite widespread and may co-exist with weak surface hoar or facets. This variably reactive interface is the critical layer to watch in the region and it has caught a few people by surprise in recent days. A few buried surface hoar layers exist in the top 120 cm in drier areas on the west side of the region near Rossland. In other areas the notable early January surface hoar layer is 100-190 cm deep and poses a low probability/ high consequence threat. It should remain on your radar, especially in thin snowpack areas and during periods of significant warming or rapid loading.

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