Bulletin d’avalanche

Purcells

Mar 24 – 25, 2021Avalanche Canada
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Archivé · expiré 6 years ago

Danger d’avalanche

Fri
Sat
Alpin
2 · Modéré
Limite forestière
1 · Faible
Sous la limite
1 · Faible
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Points saillants

Look for cold dry snow on north facing terrain at upper elevations, but be wary as this may also be where wind slabs linger.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Steady wind from the southwest and northwest has likely left some unstable slabs on steep alpine slopes.

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    1.5–2.5

    Where cornices exist they pose a threat both from the potential to collapse under your feet (or machine) and from the potential to send large chunks of snow far down a slope. If anything can trigger old stubborn persistent weak layers, it's a large falling cornice.

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

WEDNESDAY NIGHT: Partly cloudy with some light flurries on the western slopes of the Purcells, 20 km/h northwest wind, treeline temperatures drop to -6 C.

THURSDAY: Mix of sun and cloud with some light flurries but no notable accumulations of snow, 20-30 km/h northwest wind, treeline temperatures around -3 C.

FRIDAY: Mix of sun and cloud with some light flurries but no notable accumulations of snow, 20-30 km/h west wind, treeline temperatures around -3 C.

SATURDAY: Mix of sun and cloud, 20-40 km/h southwest wind, freezing level climbing to 2000 m, treeline temperatures around -1 C.

Avalanche Summary

Recent avalanche activity has primarily been small (size 1-1.5) wind slab avalanches, dry loose sluffs, and cornice falls. These have occured on a range of aspects, and will continue to be possible on slopes that have recently been wind loaded. A few larger (size 2) wind slab avalanches were observed on steep south-facing slopes in the Dogtooth Range on Wednesday morning. On Tuesday there was also a small (size 1) human triggered slab near Invermere on a north aspect at 2000 m. This avalanche ran on a 15 cm deep surface hoar layer underneath the recent snowfall.

Snowpack Summary

Steady wind from the southwest and northwest has likely left wind slabs in lee features. 20-40 cm recent snow covers dry and compacted snow on polar aspects above 1800 m and crusts on solar aspects. Storm snow has been sluffing easily on the crust. Large cornices loom over alpine ridgetops.

A persistent weak layer of facets 40-60 cm deep that was buried in mid-February was reactive in the north of the region earlier this month, but since the first week of March, only a few avalanches have been reported on this layer resulting from large triggers such cornice falls. There are several other layers deeper in the snowpack composed of old surface hoar, facets and/or crusts, all of which have been recently unreactive.

Terrain and Travel

  • Be alert to conditions that change with elevation, aspect and exposure to wind.
  • Carefully evaluate steep lines for wind slabs.
  • Minimize your exposure time below cornices.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.

Régions couvertes