Avalanche forecast

Purcells

Feb 10 – 11, 2023Avalanche Canada
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Archived · expired 4 years ago

Avalanche danger

Sun
Mon
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Persistent slab avalanches continue to be reported in this region. The message remains the same – a complex, and generally weak snowpack is best managed by continuing to stick to lower angled, low consequence terrain.

Avalanche problems

  • Wind Slabs

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

    Recent new snow combined with wind has formed fresh wind slabs in lee terrain features.

  • Persistent Slabs

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

    Several weak layers in the upper and middle portions of the snowpack are at prime depths for human triggering. Stay disciplined and choose low consequence lines. Use extra caution in steep, wind-sheltered terrain where buried surface hoar is most likely to be preserved.

  • Deep Persistent Slabs

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

    It remans possible that riders could trigger a weak layer of facets near the base of the snowpack. The most likely area to trigger it is in shallow areas with variable snow depths. Avoid thin and rocky start zones and select routes that avoid traveling through or under large avalanche paths.

Confidence

Moderate

Avalanche Summary

On Wednesday there were two reports of natural deep persistent slab or persistent slab avalanches to size 3. These were viewed in the central part of the region and in the Dogtooth range. It seems both were triggered by heavy loads (cornice fall and wind slab avalanche stepping down) on north east and east aspects at 2500m.

There were also reports of wind slab avalanches to size 1.5 and 2.5 on north and east aspects in the alpine.

The possibility remains of triggering facets near the base of the snowpack, particularly on shallow, rocky slopes.

Snowpack Summary

20-50 cm of snow since late January is settling, or has been redistributed by moderate southwest wind. This overlies another layer of windslab, or surface hoar sitting on facets or a thin sun crust.

50-70 cm below the surface, the mid-pack contains a layer buried in early to mid January that remains a concern. It mostly exists as surface hoar, but facets or a crust may also be present.

A layer from late November is found 75 to 150 cm deep and is part of a generally weak, faceted snowpack.

Snowpack depths range between 80 and 180 cm at treeline, with the shallowest depths found on the eastern edge of the region.

Weather Summary

Thursday Night

Mainly cloudy with isolated flurries, accumulation 1-3cm. Moderate southwest ridgetop wind. Treeline temperature around -7 °C.

Friday

Mainly cloudy with scattered flurries, accumulation 3-5cm. Moderate to strong southwest ridgetop wind. Treeline temperature around -4 ºC. Freezing level rising to 1300m.

Saturday

Mainly cloudy with isolated flurries. Light to moderate west ridgetop wind. Treeline temperature around -5 ºC. Freezing level rising to 1200m.

Sunday

Mostly cloudy. Light to moderate west and southwest ridgetop wind. Treeline temperature around -6 °C. Freezing level around 1100m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
  • Approach lee and cross-loaded slopes with caution.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Uncertainty is best managed through conservative terrain choices at this time.

Regions covered