Avalanche forecast

Purcells

Nov 23 – 24, 2013Avalanche Canada
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Archived · expired 13 years ago

Avalanche danger

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

Forecasts are based on limited observations. Dig down, test weak layers and keep an eye on rising temperatures.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–3
    Recent winds have dominated alpine and treeline areas. Touchy wind slabs are likely found lee of terrain features.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–4
    Rider triggered slab avalanches are failing on a crust that sits 60-120 cm below the surface.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–3
    Surface snow may become moist and weak with warm alpine temperatures and sunshine. Small loose wet avalanches could trigger the persistent weak layer buried deeper in the snowpack.

Confidence

Fair - Due to the number of field observations

Weather Forecast

High pressure will strengthen though the forecast period bringing strong inversions (warmer temperatures) at upper elevations. No precipitation expected.Sunday/ Monday: A mix of sun and cloud. Alpine temperatures 0 degrees. Freezing levels near 2500 m. Ridgetop winds from the NW. Tuesday: Mainly sunny. Alpine temperatures below 0 degrees. Freezing levels falling to 1300 m. Ridgetop winds will be light from the NW.

Avalanche Summary

No recent avalanches reported. Earlier in the week a widespread cycle up to size 3 occurred throughout the region. Many of these avalanches ran on the October crust/ facet combo near the base of the snowpack.

Snowpack Summary

The average snowpack depths at upper elevations are near a metre or more. Wind slab problems likely exist on lee slopes.A bigger concern deeper in the snowpack is a melt-freeze / rain crust that formed early October. This is generally found from 70-120 cm down, with facetted (sugary) crystals above and below that are bonded poorly. The crust/ facet combo may be more predominant on Northerly aspects and allow for wider propagations, especially in places that have smooth ground cover (glacier ice, grassy slopes, rock slabs etc.).Snowpack conditions may change and deteriorate as temperatures rise in the alpine.

Regions covered