Bulletin d’avalanche

North Columbia

Nov 27 – 28, 2022Avalanche Canada
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Archivé · expiré 4 years ago

Danger d’avalanche

Tue
Wed
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Points saillants

Touchy new slabs from Saturday night's storm might be the lead story, but the plot thickens with the chance for surface instabilities to trigger the weak layer sitting a bit deeper. Choose terrain that prevents you from finding out which layer is performing.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    1–2

    Touchy new storm slabs will be forming overnight Saturday, but the new snow is also loading a variable interface that has produced many avalanches and signs of instability since it was buried. By Saturday morning it may be buried 60-80 cm deep in some areas and capable of producing large, destructive avalanches.

    Avalanche hazard is unlikely anywhere snowpack depths have yet to overcome ground roughness like brush, trees, and rocks.

Confidence

Moderate

Avalanche Summary

A MIN report from Friday in 12 Mile, just outside this forecast region gives a good indication of the potential reactivity at the mid-November interface described in our snowpack summary. Significantly more snow is sitting on this layer in the central and especially northern Columbias.

A day earlier, many more signs of instability were noted elsewhere in the region, such as the Nelson area, Revelstoke, Sicamous, and very likely throughout the rest of the region.

The destructive potential of avalanches failing at this interface will be increased by Saturday night's snowfall.

Please share your observations to the MIN!

Snowpack Summary

Another 15-30 cm of new snow is expected to cover the region by early morning Sunday. The north can again expect the greatest accumulations. The new snow adds to 25-40 cm of snow from storms on Tuesday and Friday.

The new and recent snow collectively overlies a variety of surfaces that formed mid-November, including weak surface hoar in sheltered treeline terrain, sugary faceted grains, a thin sun crust on steep solar aspects, or bare ground in wind-exposed terrain.

We're still gathering information about the reactivity at this variable interface since the added load from Friday's storm, but the greatest concern may be where surface hoar is present (think sheltered, shaded areas). Additional loading from forecast snowfall could prove critical here.

Average snowfall depths are around 40 to 70 cm below treeline and 90 to 140 cm in the alpine.

Weather Summary

Saturday night

Cloudy with moderate to heavy snowfall. Light to moderate southwest winds.

Sunday

Cloudy with continuing flurries or leaving 15-30 cm of new snow, including overnight amounts. The north of the region is strongly favoured for heavier accumulations. Light to moderate west or northwest winds, easing over the day. Treeline high temperatures around -8 C, cooling over the day.

Monday

Mainly sunny. Light east or northeast winds. Treeline high temperatures around -12 C.

Tuesday

Increasing cloud with isolated flurries in the afternoon. Light to moderate south or southwest winds, increasing over the day. Treeline high temperatures around -16.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Closely monitor how the new snow is bonding to the old surface.
  • Make observations and assess conditions continually as you travel.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.

Régions couvertes