Avalanche forecast

Kootenay Boundary

Apr 1 – 2, 2012Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–6
    The increased wind and new snow have formed windslabs in lee zones at ridgecrest. These overlie a slick melt freeze crust in most locations and surface hoar on North aspects. A small windslab event could step down to the deep, persistent weakness.

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    2–7
    Cornices continue to grow. There is potential for triggering deep persistent slabs on underlying slopes.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    2–4
    Up to 70cm of new snow has fallen recently. At lower elevations, expect moist sluffing, while higher up (drier snow) the storm slab is more cohesive. A small storm slab event (or sluff) could step down to the deep weaknesses.

Confidence

Fair - Intensity of incoming weather is uncertain on Tuesday

Weather Forecast

MONDAY: Light precipitation throughout the day with intensity increasing late afternoon into the evening. Freezing level 1200-1600m. Winds light to moderate from the south. TUESDAY: Moderate to heavy precipitation combined with moderate to strong southerly winds. Freezing level 1500-1800m. WEDNESDAY: Light precipitation with freezing levels at 1200-1500m.

Avalanche Summary

The region has been very active with avalanches the past several days. Natural, explosive and human triggered avalanches have been reported up to size 2.5. Reports come from all aspects, with a bias to north facing slopes. At lower elevations (where the surface is moist) these are running as loose events and at higher elevations the new snow is propagating as a slab. Remote triggering has also been observed. There was one sympathetic triggered avalanche that released on the early February weakness 150cm deep. Also, several large avalanches (up to size 4.0) were explosive controlled recently. These failed from northeast to northwest aspects at ridgecrest and ran full path to valley bottom, ending as deep moist deposits.

Snowpack Summary

Up to 70cm of new snow has fallen since March 26. Shears within the upper storm snow are tightening with the persistent warm temperatures, although a reactive graupel layer down 25-40 remains. The March 26 interface is a melt freeze a crust on all aspects except true north treeline and alpine, where small surface hoar (5mm) is present in sheltered places. The bond at this interface is gaining strength, with lingering concerns on true south aspects where the crust is thickest and where the surface hoar lurks. At lower elevations, the consistent high freezing levels have kept the new snow heavy and moist. The deep, persistent early February surface hoar lingers in the snowpack giving sudden results in testing. Concern remains with heavy triggers (cornice), step down avalanches and rapid loading from intense precipitation, strong winds or sun.

Regions covered