Avalanche forecast

South Rockies

Apr 5 – 6, 2012Avalanche Canada
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Avalanche danger

Sat
Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–5
    Wind slab avalanches are present below ridge crest and behind mid slope features like ribs. Wind slab avalanches have the potential to step down and trigger avalanches anywhere in the upper meter of the snowpack.

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    3–7
    Large cornices hang over most lee slopes. Cornices may become weak with daytime heating so pay attention to what's happening above you & bear in mind that cornice fall could initiate large avalanches failing on persistent weak layers.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–4
    Periods of sun are expected Friday & the new snow will likely react quickly to the strong solar input, producing loose snow avalanches.

Confidence

Fair - Due to limited field observations

Weather Forecast

Cool dry air out of the north brings light convective flow to much of the province Friday & Saturday. Friday: Sunny periods in the morning give way to broken cloud in the afternoon. Expect the occasional convective burst of snow. No significant precipitation is expected. Ridge top winds moderate out of the NW. Freezing level tops out around 1800 m. Saturday: Freezing level starts at the surface, climbs to 1700 m, then returns to the surface overnight. Winds moderate westerly at all elevations.. Sunday: Flow switches from north to south Saturday evening resulting in slightly warmer temps Sunday. Freezing level climbs to around 2000 m. Winds light out of the east at treeline, moderate W at ridge top.

Avalanche Summary

No avalanche activity reported from the region Wednesday or Thursday. Control work in the Fernie area Thursday produced avalanches to size 2 with most activity being limited to the 20 cm of storm snow. The storm snow was reportedly quite sensitive to ski cutting, numerous size 1.5 avalanches were triggered in this fashion on N, NE & E facing slopes. A few deeper avalanches were triggered by control work under headwall features too.

Snowpack Summary

10 - 20 cm of snow fell in the region Wednesday. The new snow was accompanied by moderate winds out of the south which created soft slabs on lee aspects. There was a good re-freeze reported from Monday night and again on Tuesday night, that has resulted in a supportive melt-freeze crust on all aspects up to about 2200 metres. North aspetcs may be dry down to about 2000 metres in some areas. Southerly aspects became moist in the alpine on Tuesday, but snowballing and wet point releases were limited to size 1.0. Forecast new snow and strong winds are expected to create new windslabs and add a new load to storm slabs. Deep weak layers may continue to be triggered by large loads like cornice falls or storm slab avalanches.

Regions covered