Lawinenlagebericht

North Columbia

Apr 3 – 4, 2017Avalanche Canada
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Lawinengefahr

Wed
Thu
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Kernpunkte

Storm slabs and pockets of wind loaded snow may continue to be reactive to human triggers. Cornices may become weak and release naturally during the heat of the day; avoid slopes below cornices.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely - Possible
    Größe
    3–4
    A cornice fall or smaller slab avalanche could trigger large, destructive avalanches on deeply buried weak layers. The likelihood of this happening will increase as solar warming weakens unstable cornices and storm slabs over the course of the day.

  • Storm Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible - Likely
    Größe
    2–3
    Recent snow and wind have formed storm slabs that may remain reactive to human triggering. This problem is more pronounced in wind affected areas at higher elevations, so be vigilant for signs of recent wind loading.

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2
    Expect a good overnight re-freeze down to valley bottoms. The combination of daytime warming and strong solar radiation may result in loose wet avalanches at lower elevations, and on sun exposed slopes.

Confidence

Moderate - Timing or intensity of solar radiation is uncertain on Tuesday

Weather Forecast

Overnight: High overcast with light winds and freezing down to valley bottoms. Tuesday: Mix of sun and cloud with moderate southwest winds and daytime freezing up to 1400 metres. Wednesday: Overcast with afternoon flurries and moderate southwest winds. Daytime freezing up 1800 metres. Thursday: A few cm of new snow by morning. Winds becoming light and daytime freezing around 1800 metres.

Avalanche Summary

Natural storm slab avalanches up to size 3.0 were reported on Sunday from both the Monashees and the Selkirks. Natural and explosives controlled cornice falls released up to size 2.5 on their own, and up to size 3.0 where they pulled a slab on the slope below. A solid overnight re-freeze down to valley bottoms is forecast, setting up a spring melt-freeze cycle over the next few days.

Snowpack Summary

10-20 cm of recent snow now overlies a crust below about 2200 metres on (higher on solar aspects) and moist snow below about 1700 metres. Below the new snow interface, storms over the past week brought 40-60 of snow to the region. Several other crusts as well as moist snow are likely to exist within this storm snow, mainly at lower elevations and on solar aspects. Moderate to strong southwest winds during and since the storm formed wind slabs on leeward slopes as well as fragile cornices along ridgelines. 90-130 cm of accumulated snow now overlies a more widespread rain crust below 2000 m and sun crust on solar aspects at higher elevations. At higher elevations, the February weak layers are down 160-200 cm and the deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack. These layers were active during a storm in mid-March and produced some very large avalanches. Occasional deep releases were also reported in late March and these deeply buried weaknesses remain a serious concern as solar radiation and warming temperatures begin to penetrate the snowpack at increasingly higher elevations.

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