Avalanche forecast

Purcells

Mar 17 – 18, 2014Avalanche Canada
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Archived · expired 13 years ago

Avalanche danger

Wed
Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–4
    Recent storm accumulations may take longer to bond due to the presence of buried surface hoar and crusts. Watch for increased triggering in wind-exposed terrain, or when solar radiation is strong.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–4
    With forecast sunny breaks on Tuesday loose wet avalanches will become likely on sun-exposed slopes. Pushy loose wet activity may also trigger deeper, more destructive avalanches.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    3–5
    Recent storm accumulations have added stress to a number of persistent weaknesses which exist in the mid and upper snowpack. Any of these weaknesses would be destructive if triggered. Watch for increased sensitivity with forecast solar radiation.

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Tuesday

Weather Forecast

Overview: A ridge of high pressure will bring dry conditions to the region on Tuesday. A frontal system will bring moderate snowfall on Wednesday before the dry ridge rebuilds on Thursday.Tuesday: Mix of sun and cloud / Light to moderate northwest winds / Freezing level at 1500mWednesday: 10-20cm of snow / Moderate to strong southwest winds / Freezing level at 1400mThursday: Mix of sun and cloud with light flurries / Moderate northwest winds / Freezing level at 600m

Avalanche Summary

Although observations were limited on Saturday, a size 3 natural persistent slab avalanche was triggered on a south aspect in the north of the region. The avalanche is thought to have failed on a recently buried crust/surface hoar interface. On Sunday observations were somewhat limited; however, widespread storm slab activity to size 2 was reported in the north of the region where recent accumulations were higher. Further south in region several size 1.5 natural storm slabs were reported with a few explosive controlled storm slabs to size 2.

Snowpack Summary

Up to 45cm of recent storm snow exists and has been blown by strong winds into much deeper deposits in lee terrain. These recent storm accumulations overlie crusts on previously sun-exposed slopes and surface hoar in shaded terrain. Rain at lower elevations continued to saturate the snowpack and lower elevation surfaces may now exist as a refrozen crust. Below the new snow, 60-100cm of settled snow has been bonding poorly to buried surface hoar and crusts. The deeper facet/crust persistent weakness buried at the beginning of February, now down 60 to 160cm, has been highly variable in terms of reactivity and is still very difficult to trust. Needless to say, any avalanche at these deeper, persistent interfaces would be large and destructive.Weak basal facets exist in many areas, but without a large load, triggering now is unlikely.

Regions covered