Bulletin d’avalanche

Sea To Sky

Mar 19 – 20, 2012Avalanche Canada
Voir sur la carte
Archivé · expiré 15 years ago

Danger d’avalanche

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

Points saillants

Another storm hits the region tonight into Tuesday. Strong winds and new snow has increased the avalanche danger.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    1–6
    Wind slabs lurk below ridges, behind terrain features and in gullies. They may be buried by new snow, making them hard to spot. Large cornices have formed, and threaten slopes below.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely - Certain
    Taille
    1–6
    New storm slabs will build on Tuesday. Initially they may have a poor bond to last weeks storm snow which is deep and variable, and may not have fully settled.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    4–8
    Persistent weaknesses still have the potential to create very large, destructive avalanches if triggered. Possible triggering mechanisms include a person/sled on a thin snowpack spot, cornice fall, or step-down avalanche.

Confidence

Fair - Intensity of incoming weather is uncertain on Tuesday

Weather Forecast

Monday overnight brings 8-15 cm of new snow. This is accompanied by strong South winds, and freezing levels near valley bottom. Tuesday: Snow amounts 15-25 cm. Ridgetop winds strong from the SW. Treeline temperatures near -5. Freezing levels near 500 m. Wednesday: Due to the convective weather pattern, scattered light-moderate snow accumulations are expected. Ridgetop winds moderate from the SW. Treeline temperatures near -8. Freezing levels valley bottom. Thursday: Cloudy in the morning, broken skies in the afternoon. Light afternoon flurries near 5 cm. Freezing levels valley bottom in the morning, rising to 700 m in the afternoon.

Avalanche Summary

Last week was very active with natural avalanche activity up to size 3.5. Additionally we had several reports of rider involvements and close calls. Some were failing on the mid-February persistent weakness. The size and frequency of avalanches seems to have decreased slightly over the weekend as storm slabs and wind slabs slowly gained some strength. On Sunday a skier accidently triggered a size 1.5 from a NE aspect, in steep rocky terrain. Avalanches were also triggered naturally and by explosives in steep, rocky terrain to size 2. Avalanche activity may increase with additional snow and wind on Tuesday. The danger ratings will rise.

Snowpack Summary

Last week, 100-180 cm storm snow fell, accompanied by strong south-easterly to south-westerly winds. Storm slabs and wind slabs now appear to be slowly gaining strength. Cornices are large and threaten slopes below. A persistent weakness, formed in mid-February, continues to produce hard, sudden planar results in snowpack tests. The likelihood of triggering this layer has gone down, but very large avalanches remain possible, which could be triggered by a shallower avalanche or cornice fall. The average snowpack depth at treeline is 350 cm. With the arrival of Tuesday's storm, new storm slabs and wind slabs will develop. It may take several days for the new storm snow to settle out and start to stabilize.

Régions couvertes