Avalanche forecast

Purcells

Mar 13 – 14, 2023Avalanche Canada
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Avalanche danger

Wed
Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Storm snow blankets the region and has created reactive storm slabs at all elevations. If triggered storm slab avalanches could step down to weak layers deep in the snowpack creating large destructive avalanches. Careful snowpack evaluation, cautious route-finding and conservative decision-making are essential for a safe day out in the mountains.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    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

    10-25 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 Monday, poor visibility made for limited observations in the alpine. Several natural loose dry and storm slab avalanches were reported on steep terrain. Ski cutting produced numerous size 1.5 storm slab avalanches in open terrain.

On Saturday, a natural size 2.5 was observed at 2400 m on a northwest aspect. The avalanche was +100 cm deep and occurred on one of the persistent buried layers within the snowpack.

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

10-25 cm of storm snow overlies a plethora of surfaces including hard, 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 60-80 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

Monday Night

Cloudy with mixed precipitation, 2-6 cm of new snow at higher elevations. The Western Purcells will see an additional 15 cm. Alpine temperatures reach a low of -6 °C. Ridge wind southwest 20 km/h gusting 40 km/h. Freezing levels lower from 1700 meters to valley bottom through the night.

Tuesday

Mainly cloudy with sunny periods. Alpine temperatures reach a high of -4 °C. Ridge wind southwest 15 km/h gusting 30 km/h. Freezing levels rise to 1200 meters.

Wednesday

A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -3 °C. Ridge wind northwest 20 km/h. Freezing levels rise to 1300 meters.

Thursday

Mainly sunny. Alpine temperatures reach a high of -2 °C. Ridge wind northwest 20 km/h. Freezing levels rise to 1400 meters.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Be especially cautious as you transition into wind affected terrain.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • Avoid areas with a thin or variable snowpack.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

Regions covered