Bulletin d’avalanche

Northwest Coastal

Mar 18 – 19, 2013Avalanche Canada
Voir sur la carte
Archivé · expiré 14 years ago

Danger d’avalanche

Wed
Thu
Alpin
4 · Fort
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
Ouvrir la carte complète

Points saillants

An already touchy snowpack will likely produce natural avalanches on Tuesday as the wind picks up.

Problèmes avalancheux

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2–6
    Cornices are reported to be large and unstable, especially when temperatures become warm or the sun is out. Watch for reverse loading from outflow winds.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    3–7
    A weak layer comprising surface hoar crystals is buried around 50 cm below the surface and is reacting readily to natural and human triggers. This layer appears to have the ability to propagate over large areas of terrain.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2–6
    Recent new snow has consolidated into a slab and is reacting on steep terrain. Outflow winds have reverse-loaded slopes in some areas.

Snowpack Summary

30-60 cm of recent storm snow rests on a variety of old snow surfaces, including crusts, previous wind slabs and surface hoar. Warmer temperatures and recent winds have now set this new snow into a reactive slab, with wind slabs building in exposed lee areas. The surface hoar (buried March 9th) is reported to be well-developed and fairly widespread, at treeline and alpine elevations. Recent snowpack tests have produced sudden failures with moderate loading force at this interface. The mid snowpack is generally well settled and strong. Cornices are large and untrustworthy, especially when the sun is out.

Confidence

Poor - Intensity of incoming weather is uncertain

Weather Forecast

Synopsis: A Frontal system passes mostly to the south of this region on Tuesday night/Wednesday, bringing generally light precipitation.Tuesday: 5-10 cm new snow. Freezing level 500 m. Southwesterly ridgetop winds increasing to around 50 km/h.Wednesday: 5-10 cm new snow. Freezing level 500 m. Winds light southeasterly.Thursday: Mostly dry with some good sunny breaks. Generally light westerly winds.

Avalanche Summary

A very large (size 3.5) avalanche was triggered in Cherry Bowl in the Shames backcountry on Sunday. Click here for a full report. This slide illustrates clearly the potential for deep and destructive releases on the March 9th surface hoar layer. On Saturday, natural slab avalanches were reported up to size 3 on all aspects in the alpine. Solar aspects were particularly reactive and daytime warming triggered slides on the surface hoar layer from March 9th buried approximately 45 cm. Cornice releases were also numerous and triggered slab avalanches on the slopes below. On Friday, a skier triggered a size 2 avalanche on the March 9th surface hoar layer with a crown depth of 45 cm. Several other skier-triggered avalanches occurred on north and west aspects on the same weak layer.

Régions couvertes