Bulletin d’avalanche

North Columbia

Mar 15 – 16, 2022Avalanche Canada
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Archivé · expiré 5 years ago

Danger d’avalanche

Thu
Fri
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Points saillants

Storm slabs are expected to remain reactive to human-triggering in wind-loaded terrain or where slabs are sitting on a weak layer of surface hoar or a sun crust.

Start on smaller terrain features and gather information before committing to bigger terrain.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1.5–3

    20-60 cm of recent storm snow, warm temperatures, and moderate southwest winds have formed storm slabs that have been most reactive in wind-affected terrain, or where slabs are sitting on a weak layer of surface hoar or a sun crust.

    In steep sheltered terrain, small dry-loose sluffs may be reactive to human-triggering. Avoid terrain traps, such as gullies, where the consequences of a small avalanche could be serious.

Confidence

Moderate - Forecast precipitation (either snow or rain) amounts are uncertain.

Weather Forecast

A series of frontal systems coming in off the coast will bring light precipitation throughout the week.

Tuesday Overnight: Mainly cloudy, light precipitation. Localized areas up to 15 cm accumulation. Moderate to strong westerly winds. Freezing level dropping to 800 m. 

Wednesday: Partially cloudy, light precipitation. Light to moderate westerly winds. Freezing level rising to 1500 m.

Thursday: Mainly cloudy, light precipitation. Localized areas up to 15 cm accumulation. Moderate to strong southwesterly winds. Freezing level 1500 m.

Friday: Partially cloudy, light precipitation. Moderate to strong southwesterly winds. Freezing level rising to 1500 m.

Avalanche Summary

On Monday, numerous skier-triggered storm slab avalanches occurred throughout the region. These storm slabs were most reactive in wind-loaded terrain or where they were sitting on a sun crust or a weak layer of surface hoar. A natural avalanche cycle up to size 3 occurred on Monday afternoon with heavy snowfall, wind and warm temperatures. 

Numerous natural and skier-triggered storm slab avalanches up to size 2.5 were reported over the weekend. 

Riders may get surprised by widely propagating storm slabs that are sitting on a weak layer of facets/crust or surface hoar.

Snowpack Summary

Continued light precipitation will add to 30-60 cm of recent settling storm snow. In the alpine and treeline, southwest winds have created deeper deposits of slab in lee areas. Storm snow tapers rapidly below treeline, where moist snow or a melt-freeze crust can be expected from rain and warm temperatures.

The recent new snow is sitting on various surfaces, including hard wind-affected snow, facetted snow, sun crusts on southerly slopes, and surface hoar on shady or sheltered slopes. 

The late February persistent weak layer combination of crust, facets and surface hoar is down 30-40 cm. Reports suggest this layer is not a problem in most areas.

Two persistent weak layers from mid-February and late January are buried 50-120cm deep. No recent avalanches have been reported on these layers.

Terrain and Travel

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Be especially cautious as you transition into wind affected terrain.
  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

Régions couvertes