Avalanche forecast

South Rockies

Feb 16 – 17, 2021Avalanche Canada
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Avalanche danger

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

Use conservative decision-making on the BC side where surface hoar exists at treeline. Otherwise, watch out for wind slabs in unusual places created by wind from variable directions. Read our latest forecaster blog "Managing Moderate".

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Look out for wind slabs in unusual places. There have been some localized moderate to strong winds from variable directions. These winds have redistributed loose snow developing wind slabs in lee features, especially in the alpine and open areas at treeline. Newer reactive wind slabs will be slow to bond where they sit over cold sugary facets. There is also potential for wind slabs to step down to the late January persistent layer in isolated areas.

    In sheltered zones the surface snow is becoming faceted and sugary and sluffing should be expected in steep terrain.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–2

    40-65 cm of snow sits above a buried weak layer of surface hoar, facets, and a crust (depending on elevation and aspect). Reports suggest the surface hoar interface at treeline in the Elk Valley is the biggest repeat offender, and things have been most reactive on northerly and easterly aspects, but don't let your guard down elsewhere. 

    Small terrain features are producing small avalanche results, bigger features could produce larger more dangerous avalanches. These kinds of avalanches can happen in surprisingly mellow terrain and be triggered from a distance away.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

MONDAY NIGHT: Mostly cloudy with clear periods, light northwest wind, temperature low -15 C.

TUESDAY: Sunny with cloudy periods, trace of new snow, light northwest wind, temperature high -9 C.

WEDNESDAY: Mix of sun and cloud, light northwest wind, temperature high -8 C.

THURSDAY: Mix of sun and cloud, light westerly wind, temperature high -8 C.

Avalanche Summary

Several skier triggered wind slab avalanches up to size 1.5 were reported on Sunday on usually and reverse loaded terrain features. Natural avalanche activity of up to size 3 was reported as well dating a couple days back. Reports on whumpfing and cracking of the upper snowpack were varied. Some parties experienced whumpfs and cracks (see this MIN report) whereas others didn't (see this MIN report).

A skier accidentally triggered a size 1.5 wind slab in a reverse loaded feature on the Alberta side of the region on Saturday.

There are recent reports in the South Rockies region of human triggered avalanches on a persistent weak layer of feathery surface hoar. One of the groups made a MIN report for us, check it out. 

Snowpack Summary

The snow surface is wind affected, especially in the alpine and open areas at treeline. Cold temperatures promote faceting of the snow surface. A persistent weak layer lurks 40-65 cm below the surface. In some places it consists of surface hoar, in other places just facets, or crust/facet combinations. Reports suggest the surface hoar interface at treeline in the Elk Valley is the biggest repeat offender, and things have been most reactive on northerly and easterly aspects, but don't let your guard down elsewhere. 

A solid mid-pack sits above deeply buried decomposing crust and facet layers near the bottom of the snowpack. Though unreactive under the current conditions, steep rocky slopes and shallow snowpacks should still be approached with caution.

Terrain and Travel

  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • If triggered, loose dry avalanches may step down to deeper layers resulting in large avalanches.

Regions covered