Avalanche forecast

Purcells

Dec 23 – 24, 2012Avalanche Canada
View on map
Archived · expired 14 years ago

Avalanche danger

Tue
Wed
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
Open full map

Highlights

Lower danger ratings in the alpine should not be seen as carte blanche for bigger terrain.  See the forecaster's blog for some ideas about approaching the mountains this week.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    2–6
    In the alpine wind slabs up to 70 cm in depth are still a concern, especially in steep unsupported terrain.  Pay attention to what the winds are doing.  Even a short burst of wind has the potential to create touchy shallow wind slabs.

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    1–3
    New snow and wind has fueled significant cornice growth. Although unlikely, the right chunk of falling cornice has the potential to kick off a wind slab avalanche in steep terrain.

Confidence

Good

Weather Forecast

Monday: Light ridgetop winds out of the E. No Snow. 1500m temp: -15 Freezing level: SurfaceTuesday: Light SE ridge top winds. 1500m temp -13 No snow. Freezing Level: SurfaceWednesday: Light SW ridge top winds. Treeline temp -13. No snow. Freezing Level: Surface

Avalanche Summary

No large avalanches were reported yesterday.  There were however a few reports of both natural and skier triggered avalanches to size 1.5 in wind loaded features.  Cornices were also reported to be touchy in the north of the region.

Snowpack Summary

In the last four days the north of the region received 30 - 50 cm while the zone closer to the Purcell Wilderness Conservancy received closer to 80 cm. Winds picked up Wednesday/Thursday of last week forming large wind slabs in the Alpine that produced a limited avalanche cycle to size 2 that persisted through Friday.  It sounds like these slabs are settling out but I'm still suspect of them, especially on steep unsupported features. New (relatively) thin wind slabs involving Saturday nights snow may still be an issue Monday. Cornices are also a problem at the highest elevations. The mid-pack is reported to be settling well. I haven't heard of any test results involving the late November surface hoar in the last five days. The early November crust, near the base of the snowpack has also been inactive as of late. It's important to note that professionals are still cautious about these lingering persistent slab problems, but the likelihood of triggering is low. Be wary of steep complex terrain with a shallow snowpack, where triggering a persistent weakness is more likely.

Regions covered