Bulletin d’avalanche

South Coast Inland

Apr 8 – 9, 2018Avalanche Canada
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Archivé · expiré 8 years ago

Danger d’avalanche

Tue
Wed
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Points saillants

Freezing levels will rise over Monday along with sunny patches in the afternoon. The warming will weaken the snow and increase the likelihood of triggering slabs, cornices, and loose wet avalanches. Expect the hazard to rise over the day.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2
    Recent snowfall has formed new slabs. Expect thicker slabs in lee features due to strong southerly winds. Slab or loose wet avalanches could release naturally when the sun is out or the air temperature warms.

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–3
    Cornices are very large and fragile. Give them a large berth when on ridges and avoid travelling underneath them, as they can trigger large avalanches on slopes below.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    2–3
    A weak layer buried 40 to 70 cm is still surprising people and producing large and destructive avalanches. Be particularly cautious around upper treeline and alpine terrain on shady aspects, where this layer is most likely to be a problem.

Confidence

Moderate -

Weather Forecast

MONDAY: Cloudy with light morning snow and afternoon clearing, accumulation trace to 10 cm, light southwesterly winds, alpine temperature -4 C, freezing level 1500 m rising to 2000 m by late afternoon.TUESDAY: A mix of sun and cloud early morning then mostly cloudy with rain switching to snow at higher elevations, accumulation 10 mm, moderate to strong southerly winds, alpine temperature 0 C, freezing level 2600 m dropping to 1700 m over the day.WEDNESDAY: Mostly cloudy with light snowfall, accumulation 5 to 10 cm, light southeasterly winds, alpine temperature -4 C, freezing level 1600 m.

Avalanche Summary

Many loose wet avalanches were observed on all aspects up to treeline in steep terrain on Saturday.On Friday, a large (size 2.5) persistent slab avalanche was triggered by a cornice on a northeast aspect around 1900 to 2200 m.  The slab likely released on the weak layer described in the Snowpack Summary.  Small to large (size 1 to 2) wind slabs were also reactive to skiers and large loads, generally failing in alpine terrain in immediate lee terrain features.  Loose wet avalanches were observed across the region on all aspects to size 1.5.

Snowpack Summary

Around 10 to 20 cm of recent snow and strong southwesterly winds created new slabs at higher elevations.  This snow overlies a melt-freeze crusts on sunny aspects and all aspects to treeline, and dry snow on shaded aspects in the alpine.  On ridges, cornices are reported to be large and fragile. At low elevations below treeline, precipitation fell as rain and created moist or wet snow conditions.A weak layer consisting of surface hoar, facets, or a sun crust from late March is now buried about 40 to 80 cm. This layer is spotty in its distribution. It is mostly likely to be problematic on shady aspects between 1900 m and 2250 m.The mid and lower snowpack are strong and well-settled.

Régions couvertes