Avalanche forecast

Purcells

Mar 14 – 15, 2023Avalanche Canada
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Avalanche danger

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

Storm snow and strong southwest winds have created dangerous avalanche conditions at alpine and treeline. Use extra caution when transitioning into wind affected terrain, where storm slabs remain reactive to human triggering.

Avoid thin, rocky, wind effected areas where triggering slabs is more likely. If triggered storm slabs may step down to deep weak layers resulting in large destructive avalanches.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    1.5–3

    Numerous weak layers from January and February exist at all elevations on a variety of aspects. On shaded slopes, these layers generally present as surface hoar, and on sun-exposed slopes they present as facets and a crust.

    Avalanches triggered on these layers can step down to the facets at the bottom of the snowpack resulting in a very large avalanche.

    These layers can be remotely triggered. Avoid traveling below steep slopes.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2.5

    15-30 cm of storm snow has settled with warm temperatures into a reactive storm slab over a variety of surfaces. Be extra cautious on north and east slopes where southwest winds have built deeper pockets of storm slab. Storm slabs may be particularly reactive where they overlie a weak layer of surface hoar in sheltered treeline terrain.

    If triggered, storm slab avalanches may step down to deeper weak layers resulting in large avalanches.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2.5–4

    The base of the snowpack remains very weak. Very large human triggered avalanches are possible at treeline and above. Avoid shallow and rocky areas, where the snowpack depth is highly variable. This is a very concerning avalanche problem and should stay in your mind when traveling in the backcountry.

Confidence

Moderate

Avalanche Summary

On Sunday, good visibility revealed a widespread natural avalanche cycle from within the storm. Numerous storm slab and wind slab avalanches were observed on all aspects in the alpine and at treeline, up to size 2.5. Three natural deep persistent slab avalanches were observed in the Golden area, size 2.5-3, in steep, rocky terrain at 2400m.

If you head out in the backcountry, let us know what you are seeing by submitting a report to the Mountain Information Network.

Snowpack Summary

15-30 cm of storm snow is being redistributed by southwest winds. Storm snow overlies a plethora of surfaces including wind-affected surfaces in open areas, surface hoar and facetted snow in sheltered areas and a sun crust on steep solar slopes.

Buried surface hoar sits 70-90 cm deep in sheltered terrain features, and a thin sun crust exists at the same depth on steep south-facing terrain. Several other layers from January can also be found in the top 100cm of the snowpack.

The lower snowpack is made up of a widespread layer of large, weak basal facets and depth hoar in some areas. this weakness has been responsible for a number of recent very large, destructive avalanches and will continue to be a concern.

Weather Summary

Tuesday Night

Mainly clear skies. Alpine temperatures reach a low of -10 °C. Ridge wind southwest 15 km/h. Freezing levels drop to valley bottom.

Wednesday

Mainly cloudy with sunny periods and isolated flurries, trace accumulation. Alpine temperatures reach a high of -4 °C. Ridge wind northwest 20 km/h gusting 35 km/h. Freezing levels rise to 1300 meters.

Thursday

Sunny. Alpine temperatures reach a high of -2 °C. Ridge wind variable 15 km/h. Freezing levels rise to 1400 meters.

Friday

Sunny. Alpine temperatures reach a high of -2 °C. Ridge wind southerley 20 km/h. Freezing levels rise to 1600 meters.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be especially cautious as you transition into wind affected terrain.
  • Surface hoar distribution is highly variable. Avoid generalizing your observations.
  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Avoid areas with a thin or variable snowpack.

Regions covered