Bulletin d’avalanche

Northwest Coastal

Mar 12 – 13, 2019Avalanche Canada
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Archivé · expiré 8 years ago

Danger d’avalanche

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

The snowpack needs time to adjust to the shock of a big, long awaited storm. With surface hoar and sugary facets below the new snow it may take longer than usual to stabilize.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–3
    Reports of remotely triggered wind and storm slabs on Monday suggest conditions more like a "persistent slab" problem. All the new snow is making old surface hoar and sugary facets in the upper snowpack layers to watch.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1.5–2.5
    Storm snow concern is greatest in colder areas in the north. Forecast winds focus concerns to wind loaded features.Previous weaknesses in the upper snowpack (30 - 40 cm of sugary facets) were activate during the storm; see Persistent Slabs below.

Confidence

Moderate -

Weather Forecast

TUESDAY NIGHT: Cloudy. Dry. Light west wind. Treeline temperatures around -6 C.WEDNESDAY: Moderate to strong south wind. Treeline temperatures around -8 C. Snow starting late in the day and overnight; 10 to 15 cm accumulations by Thursday morning. Cloudy.THURSDAY: Moderate to strong southwest wind. Treeline temperatues -5 to -10 C. Light snow with an additional 5 to 10 cm. CloudyFRIDAY: Moderate south wind. Warmer with treeline temperatures approaching zero. Trace new snow. Cloudy.

Avalanche Summary

One size 2 windslab in the north of the region is worth noting: it was remotely triggered from 100 m away suggesting some sort of a persistent slab structure that won't heal overnight.In the south part of the region clouds limited observations but avalanche reports include numerous natural size 2 avalanches on all kinds of terrain 35 degrees or steeper, numerous remotely triggered size 2 slides. I suspect we'll learn more when the visibility improves and people see more terrain.

Snowpack Summary

Monday's widespread and reactive storm slabs and wind slabs should be settling down by Wednesday with the exception of colder, more northerly areas which have significantly more "wintery" temperatures. Expect instabilities to last longer in places like Bear Pass or Ningunsaw.The 40 to 60 cm of storm snow buried a wide variety of surfaces with the key idea being they're pretty much all crappy. Rule of thumb: the longer snow is exposed on the surface the less likely it'll bond when buried. Recently covered were surface hoar, sun crusts, and a widespread weak faceted (sugary) upper snowpack. It seems the old surfaces (aka Feb 19 surface hoar / facets) were as much the critical weak interface as the bottom of the storm snow.The lower snowpack is generally strong.

Régions couvertes