Bulletin d’avalanche

South Columbia

Apr 1 – 2, 2017Avalanche Canada
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Archivé · expiré 10 years ago

Danger d’avalanche

Mon
Tue
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré

Points saillants

The snowpack still hasn't adjusted to spring weather at high elevations. Keep your guard up and an eye on overhead hazards while persistent slab problems are still in play.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    2–4
    Large, destructive avalanches have recently been reported running on deeply buried weak layers. Cornice fall and smaller storm slab avalanches have been common triggers for these slides, which have the potential to reach the end of runout zones.
  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–3
    Recent snow and wind have formed storm slabs that may remain reactive to human triggering on Sunday. This problem is more pronounced in wind affected areas at higher elevations, so be vigilant for signs of recent wind loading.
  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–3
    Daytime warming and/or solar radiation may deteriorate the surface of the snowpack at lower elevations and on solar aspects. Snow that becomes moist will have the tendency to sluff from steep terrain, either naturally or with a human trigger.

Confidence

Moderate -

Weather Forecast

Saturday night: Isolated flurries with a trace to 5 cm of new snow. Light to moderate southwest winds. Sunday: Cloudy with sunny periods and isolated flurries with a trace of new snow. Light northwest winds. Freezing level to 1500 metres with alpine temperatures around -6.Monday: A mix of sun and cloud. Light northwest winds. Freezing level to 1700 metres with alpine temperatures around -5.Tuesday: Cloudy with sunny periods. Light south winds. Freezing level to 1800 metres with alpine temperatures around -4.

Avalanche Summary

Reports from Friday showed several recent (12-36 hour old) persistent slab releases to Size 3 with natural storm slab and cornice triggers. Two of these occurred on southeast aspects. Improved visibility also revealed evidence of numerous storm slabs and wind slabs having released from Size 2-3 over the same time period. Natural loose wet slides were also observed running up to Size 2.5 from steep, solar terrain.Reports from Thursday include numerous observations of storm slabs and wind slabs releasing naturally, with natural cornice falls, skier traffic as well as with ski cutting and explosives control as triggers. Sizes ranged from 1-2.5 and crown fractures generally from 30-60 cm in depth. Northeast to northwest aspects were the most active.On Wednesday, storm slabs proved reactive and ran naturally up to Size 2.5 with a couple larger Size 3 and 3.5. Storm slabs were also reportedly reactive to skier triggers up to size 1.5 at treeline elevations.

Snowpack Summary

About 10 cm of new snow fell over Friday night and Saturday morning, burying a temperature crust at about 1900 metres and below as well as sun crust all the way into the alpine on most solar aspects. The new snow brings recent storm snow totals at upper elevations to 40-60 cm. This storm snow is dry up high and moist at 1800 m and below. 90-130 cm of accumulated snow now overlies a rain crust below 2000 m and sun crust on solar aspects at higher elevations. New wind slabs are developing on leeward slopes and behind terrain features and large, fragile cornices exist along ridgelines. At higher elevations, the February weak layers are down 150-190 cm and woke up during last week's storm with many avalanches stepping down to them. The deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack and a few avalanches and cornice falls have also stepped down to these layers last week resulting in some very large full depth avalanches. These layers remain a real concern while touchier wind slabs, storm slabs, and cornices continue to present the risk of acting as triggers for deeper weaknesses.

Régions couvertes