Avalanche forecast

Purcells

Nov 24 – 25, 2012Avalanche Canada
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Avalanche danger

Mon
Tue
Alpine
No rating
Treeline
No rating
Below
No rating
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Highlights

This bulletin is based on limited data. Local variations in conditions are likely to exist. Check out the Forecasters Blog for further details on interpreting early season bulletins.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–5
    Moderate SW winds have redistributed recent storm snow and has formed touchy wind slabs. Wind slabs exist on open leeward slopes and behind terrain features.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–6
    Two persistent layers exist through the region. A surface hoar layer buried 40-80cm down, and an early Nov crust buried near the base of the snowpack. The weight of a skier, or sledder hitting the sweet spot could trigger these slabs.

Weather Forecast

The ridge building over Southern BC will bring a cool dry northwesterly flow that should carry through Tuesday. Tonight and Sunday:  Clearing in the Southern part of the region and flurries on the Northern part. Light North West wind in the South and Moderate in the North. Temperatures will remain cool for the period and freezing level should remain around 800 m. Monday and Tuesday: Weather forecast stays similar on Monday except that Tuesday should warm up a bit and winds are expected to be stronger in the alpine from the same direction.

Avalanche Summary

Information came from the South Columbia region that a widespread avalanche cycle was triggered by the recent snow event with avalanches up to 2.5 in size on mainly N and NE aspects. A similar cycle could have gone through the Purcells as well, which could improve stability in those specific areas. However, if the recent load did not produce avalanches, I would keep in mind that human triggering is likely. If you and your friends have been out riding in the backcountry, and have observations to share, please send an email to [email protected]

Confidence

Poor - Due to limited field observations for the entire period

Snowpack Summary

The region got from  15 to 30 cm of snow in the recent storm. It fell with moderate winds from the South West. This has contributed to thicken the already existing wind slabs found on North and NorthEast aspects. Wind loaded slopes that haven't produced avalanches already would be the main concern for human triggering since 2 fairly deep persistent weak layers are found on all aspects and in the alpine and at treeline. The surface hoar layer is buried under approx. 60 cm, and the early season November crust is deeper, near the bottom of the snowpack ranging from 80 to 100 cm. The facet-crust layer is less reactive, however we do not have recent information about the sensitivity of the surface hoar layer.  There is still a sharp transition in snow depth from treeline to below treeline making backcountry travel more challenging under the 1300 m range.

Regions covered