Avalanche forecast

South Rockies

Mar 9 – 10, 2012Avalanche Canada
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Avalanche danger

Sun
Mon
Alpine
4 · High
Treeline
4 · High
Below
4 · High
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Highlights

Very dangerous avalanche conditions exist in this region at this time.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–5
    Recent strong winds have set up touchy wind slabs in lee terrain in exposed areas.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    3–7
    A prominent persistent weak layer from the middle of February exists in some areas, and is most prevalent in the Flathead range. If triggered, this layer has the potential to produce large and dangerous avalanches.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2–6
    Warm temperatures have promoted instability in the upper snowpack and wet or moist slabs avalanches have occurred in many areas.

Confidence

Poor - Timing, track, or intensity of incoming weather is uncertain

Weather Forecast

Saturday: 5-10 cm new snow is expected, with extreme winds gusting from the SW to 110 km/h. Freezing levels around 1800 m. Sunday: Flurries or light snowfall. Winds strong southwesterly. Freezing levels around 1300 m. Monday: Further light precipitation with strong winds and freezing levels around 1300 m.

Avalanche Summary

On Friday, a natural avalanche cycle occurred up to size 3 in response to very warm temperatures and continued loading of exposed start zones by high winds. Over the past few days, there have been several reports from in or near the region of near misses, including a snowmobiler who triggered an avalanche and was buried for around 30 minutes, remote-triggered avalanches, and slab avalanches running into unusually low-angled terrain.

Snowpack Summary

Intense warming on Thursday and Friday was making the surface snow moist in many places. 20 to 50 cm of recent storm snow has been reported from different parts of this region. Winds from the SW and the NW have set up wind slabs in lee areas in exposed terrain. The mid February surface hoar layer is now down between 40 & 100cm and is more prevalent in the west and south of the region, particularly in the Flathead. Recent snowpack tests as well as a rider-triggered avalanche on this weak layer indicate that it still has the potential to be triggered in many areas and if it is triggered, a large avalanche could result. Remote-triggering, triggering from below and triggering on low-angled terrain are also concerns. Lingering concern remains for basal facets, particularly in shallower snowpack areas with steep, rocky start zones. Cornices are becoming well developed in response to recent winds and are likely starting to droop with the warm temperatures.

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