Avalanche forecast

South Columbia

Apr 11 – 12, 2017Avalanche Canada
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Avalanche danger

Thu
Fri
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Winter continues in the alpine. A series of new storms are expected to develop new wind slabs over the next few days.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–2
    Variable wind directions over the past few days may have developed wind slabs on several aspects in the alpine and at treeline. Forecast new snow may hide recent wind slabs.

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3
    Cornices have grown large and may fall off naturally with solar effect or daytime warming. Cornice falls were responsible for triggering a number of large persistent slab avalanches last week and as recently as Saturday.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–4
    A cornice fall or smaller slab avalanche currently has the potential to trigger large, destructive avalanches on deeply buried weak layers. This is more likely to occur in thin or variable snowpack areas at higher elevations.

Confidence

High -

Weather Forecast

Overnight: Cloud and moderate southeast winds developing with freezing down to 700 metres. Wednesday: 5-8 cm of new snow with moderate southeast winds and daytime freezing up to 1600 metres. Thursday: 5-10 cm of new snow with a chance of convective flurries producing up to 15 cm in some areas. Daytime freezing up to 1700 metres. Friday: Mostly cloudy with a chance of sunny breaks in the afternoon and daytime freezing up to 1400 metres.

Avalanche Summary

Natural cornice falls were reported up to size 3.0 on Monday. There were also reports of isolated wind slabs up to size 1.0. Loose dry and loose wet avalanches to size 1.0 were reported on Sunday. 

Snowpack Summary

The recent storm snow is 30-50 cm including the snow that fell late lat week. The recent snow sits above a mix of old surfaces that include melt-freeze crusts at treeline and below and on solar aspects in the alpine. Fragile new cornice growth also occurred along ridgelines over the course of the week. Below the new snow interface, a number of storm snow and crust layers that formed over mid to late March appear to be well bonded. The February weak layers are now down about 170-220 cm and the deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack. These deep weak layers produced large avalanches with cornice falls and other heavy triggers in late March and early April. Yet another deep release was reported in the region on Saturday. This activity, although growing more sporadic, is keeping these layers an ongoing concern. They may be more likely to fail on southerly aspects during periods of strong solar radiation.

Regions covered