Avalanche forecast

Purcells

Feb 25 – 26, 2023Avalanche Canada
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Avalanche danger

Mon
Tue
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Wind affected snow can be found at all elevations. Watch for dense, cohesive slabs in all areas - especially fresh slabs forming from southwest winds.

The weak snowpack continues to produce large slab avalanches. Keep your exploration to low angle supported terrain - avoiding thin, rocky and steep features.

Avalanche problems

  • Wind Slabs

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

    Expect variable wind affected surfaces on all aspects and at all elevations. Strong north/east winds from earlier this week have now been replaced by south/west winds building fresh wind slabs where snow is available for transport.

    Watch for wind loading mid to low on slopes, and be wary of cross-loaded features. Wind affected snow may sit over a layer of surface hoar in sheltered terrain features, or over a sun crust on south facing slopes which may increase reactivity.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–4

    The base of the snowpack remains very weak. Very large human triggered avalanches are possible at higher elevations. Avoid shallow and rocky areas, where the snowpack varies rapidly from thick to thin.

    The mid and lower snowpack also contain several surface hoar layers. Due to the overall weak snowpack structure, small avalanches are likely to step down to any of the deeper weak layers creating large and destructive avalanches.

Confidence

Moderate

Avalanche Summary

Natural and explosive triggered avalanches were reported on Tuesday and Wednesday to size 3, on all aspects and elevations. While natural activity appears to have tapered off, human-triggered slab avalanches remain possible while the recent storm snow begins to bond to underlying surfaces.

Deep persistent slab avalanches continue to be periodically reported throughout the region. Including a very large skier-triggered, fatal avalanche last Thursday.

This MIN post from Thursday observed a size 3 avalanche near Golden at least 1 m deep. Likely a naturally triggered slab, the failure plane is unknown. However this still indicates the weak and unpredictable snowpack remains concerning.

Snowpack Summary

Up to 50 cm of recent snow continues to be redistributed by wind. Winds have shifted from north/east to west currently. In sheltered areas loose snow can still be found. A layer of surface hoar is now buried by 30 to 50 cm in sheltered terrain and a thin sun crust on steep south-facing terrain. In general, the mid snowpack is well consolidated and bonding.

The lower snowpack contains a number of buried weak layers such as surface hoar with variable distribution, as well as a widespread layer of large, weak basal facets and depth hoar in places. These weaknesses have been responsible for a number of recent very large, destructive avalanches and will continue to be a concern.

Weather Summary

Friday Night

Mostly clear skies with no precipitation. Moderate westerly winds. Freezing levels below valley bottom.

Saturday

Snowfall begins, delivering 1-3 cm over the day. Freezing levels remain below valley bottom with alpine highs of -15 °C. Moderate southwest winds continue.

Sunday

Up to 5 cm overnight with snow continuing over Sunday with up to 5 cm possible throughout the day. Freezing levels around 600 m. Alpine high of -5 °C with moderate to strong southwest winds.

Monday

Cloudy with moderate southerly winds easing slightly. Alpine high of -9 °C. Freezing levels around 300 m. Possible flurries.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Keep your guard up at lower elevations. Wind slab formation has been extensive.
  • Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

Regions covered