Avalanche forecast

Purcells

Mar 17 – 18, 2020Avalanche Canada
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Avalanche danger

Thu
Fri
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

A stable weather pattern is forecast for the next few days. Minimize exposure to steep slopes facing the sun during the hottest part of the day.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Moderate to strong northeast and east wind formed wind slabs at all elevations which might be reactive to human triggers. 

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    A weak layer of surface hoar sits 50-100 cm deep, within the range for human-triggering.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    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. 

Confidence

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

Weather Forecast

MONDAY Night: Clear skies, light northwest wind, alpine temperature -8 C.

TUESDAY: Mix of sun and cloud, light northwest wind, alpine temperature -1 C, freezing level 1800 m.

WEDNESDAY: Mainly cloudy, light northwest wind, alpine temperature -5 C, freezing level 1300 m.

THURSDAY: Mix of sun and cloud, light northwest wind, alpine temperature -6 C, freezing level 1200 m.

Avalanche Summary

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.

Regions covered