Bulletin d’avalanche

Purcells

Mar 22 – 23, 2019Avalanche Canada
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Archivé · expiré 8 years ago

Danger d’avalanche

Sun
Mon
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Points saillants

Seasonal weather returns. Travel conservatively and with a sense of caution, as buried weak layers may persist in the snowpack.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1.5–3
    A few weak layers still exist within the snowpack at a depth that is prime for human triggering. The recent hot weather may have influenced these layers, but time is needed to assess how much they have changed.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2
    Although the freezing level is dropping, it will likely still be high enough to keep the snowpack wet at lower elevations. Rain may further wet the snow, increasing the potential for loose wet avalanches.

Confidence

High -

Weather Forecast

FRIDAY NIGHT: Increasing clouds, light southwest wind, freezing level 2300 m.SATURDAY: Mostly cloudy with intermittent snow in the alpine and rain below, trace accumulation, light southwest wind, alpine temperature -3 C, freezing level 1800 m.SUNDAY: Cloudy with snowfall, accumulation 5 cm, light east wind, alpine temperature -2 C, freezing level 1900 m.MONDAY: Cloudy with light snowfall, accumulation 1 to 3 cm, light southwest wind, alpine temperature -3 C, freezing level 1800 m.

Avalanche Summary

Many wet loose avalanches were observed between Sunday and Thursday. They were large (up to size 3), occurred mostly on southeast to southwest aspects, and at all elevations. Many of these avalanches scoured to basal weaknesses. A notable deep persistent slab avalanche released on Wednesday, likely triggered by a cornice fall. It was 100 cm deep on a northeast aspect at 2900 m.The wet avalanche cycle will diminish over the weekend as cooler and cloudier weather prevails.

Snowpack Summary

Below around 1800 m, the snow surface should remain wet on all aspects due to rain this weekend. Above around 1800 m, the weekend's precipitation should fall as snow.  The snow will overly a melt-freeze crust on all aspects up to 2000 m and to ridgetop on sun-exposed slopes. The new snow will fall onto previously dry snow and potentially surface hoar crystals on northerly aspects above 2000 m.A few weak layers may still exist in the snowpack. A layer of faceted grains may be found 20 to 30 cm deep. It could be most problematic when in combination with hard wind-affected snow, which has been found on northerly aspects above 2000 m. Another layer of faceted grains and/or surface hoar may be found around 50 to 90 cm deep, also with a melt-freeze crust on southerly aspects. These layers haven't produced avalanches recently, but professionals are tracking them, as they have been reactive in some snowpack tests.The base of the snowpack is composed of weak faceted snow, which may be associated with a melt-freeze crust. Although this layer has been dormant for a while now, there were recent reports of a few sporadic avalanches on this layer, suggesting that it could still be triggered.

Régions couvertes