Bulletin d’avalanche

Purcells

Mar 18 – 19, 2020Avalanche Canada
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Archivé · expiré 7 years ago

Danger d’avalanche

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

A ridge of high pressure has set in for the forecast period. Expect to see mainly sunny skies. Minimize exposure to steep slopes facing the sun during the hottest part of the day.

Problèmes avalancheux

  • Wind Slabs

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

    Lingering windslabs from recent moderate to strong northeast winds may be still reactive to human triggers.

  • Loose Wet

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

    Expect loose dry or wet avalanches to run in steep terrain facing the sun during the heat of the day.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    2–3.5

    Weak facetted snow near the base of the snowpack continues to be a concern. Treat wind-scoured, rocky, shallow terrain as suspect and avoid big alpine slopes that are threatened by cornices overhead. Additionally a weak layer of surface hoar sits 50-100 cm deep, within the range for human-triggering. 

Confidence

High - Confidence is due to a stable weather pattern with little change expected.

Weather Forecast

TUESDAY Night: Mostly clear, light northwest wind, alpine temperature -8 C.

WEDNESDAY: Mix of sun and cloud, light to moderate northwest wind, alpine temperature -2 C, freezing level 1900 m.

THURSDAY: Mix of sun and cloud, light west wind, alpine temperature -6 C, freezing level 1500 m.

FRIDAY: Mix of sun and cloud, light northwest wind, alpine temperature -3 C, freezing level 1700 m.

Avalanche Summary

On Monday there was a report of a skier remotely triggering (from a distance) a size 2 deep persistent slab avalanche at 2600 m on a northwest aspect. The avalanche was triggered from a thin spot, was 40-80 cm deep and ran on depth hoar near the base of the snowpack.

On the weekend there were reports of a few natural wind slab avalanches on the weekend size 1.5 to 2.5 on north and southeast aspects in the alpine. Additionally there were reports of several loose wet avalanches to size 1.5 from steep slopes facing the sun.

Snowpack Summary

Recent moderate to strong northeast and east wind has redistributed the snow and formed wind slabs at all elevations. New snow from last week may sit on a weak surface hoar layer and a sun crust on steep solar aspects. 

A weak layer of surface hoar buried February 22 may be found 50-100 cm deep. It may sit over a crust on solar aspects. Read more about surface hoar on our forecaster blog.

Deeply buried facets lurk near the bottom of the snowpack. This layer has been responsible for sporadic deep persistent slab avalanches, usually triggered from shallow, rocky start zones.

Terrain and Travel

  • Minimize exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
  • Cornices become weak with daytime heating.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.

Régions couvertes