Avalanche forecast

Purcells

Mar 5, 2018Avalanche Canada
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Archived · expired 9 years ago

Avalanche danger

Tue
Wed
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Although the temperature is forecast to remain cool at upper elevations, when the sun does come out it can have an immediate impact on those slopes directly facing it.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2
    Recent new snow combined with wind means localized slabs on the leeward side of ridges and on cross-loaded slopes and gulleys. Anticipate old buried wind slabs on a variety of aspects.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–3
    A weak layer buried up to 90cm deep "woken-up" last week. This problem seems most reactive in south-facing terrain where buried crusts exist.

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

MONDAY: Mix of sun, cloud and isolated flurries / Light to moderate west wind / Alpine temperature -10 TUESDAY: Mix of sun and cloud / Light west wind / Alpine temperature -12WEDNESDAY: Mix of sun, cloud and isolated flurries / Light southwest wind / Alpine temperature -7

Avalanche Summary

Reports from the weekend consist primarily of natural and explosive triggered wind and storm slab avalanches size 1.5 to 2.5 in the alpine and at treeline on northerly, easterly and westerly aspects. There are also reports of two size 1 remotely triggered avalanches (from a distance) on a west aspect in the alpine. On Thursday there was a report of naturally occurring size 2.5 persistent slab avalanche on northeast facing slope at 2400m. This was reported to be triggered from a falling piece of glacier ice.

Snowpack Summary

Storm snow amounts from the last week total 50-80cm (higher amounts in the south and west parts of the region). This new snow has been redistributed into wind slabs in wind-exposed terrain by primarily south, southwest and southeast wind. 70-100cm below the surface there's a layer buried mid-February that's a sun crust on solar aspects, and spotty surface hoar on sheltered slopes. This layer looks most concerning on on solar aspects where it's associated with with small facets or surface hoar above.There are several deeper layers that have shown signs of improving but still remain suspect as low probability - high consequence avalanche problems. We are talking about surface hoar layer buried back in December and January. Near the base of the snowpack is a November crust combined with loose sugary faceted snow. These layers may "wake-up" with strong inputs such as sustained warming, sustained snowfall, large triggers (e.g. cornice fall or smaller avalanches coming down from above); human triggering is also possible in shallow snowpack areas with convoluted terrain.

Regions covered