Avalanche forecast

North Rockies

Feb 7 – 9, 2021Avalanche Canada
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Avalanche danger

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

Large human triggered avalanches are likely this weekend, particularly on slopes above 1600 m. Conservative terrain choices are critical right now. The persistent weak layer of surface hoar will be slow to gain strength.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1.5–2.5

    New snow this week has combined with moderate to strong northwest wind to create wind slabs which may remain reactive in lee terrain features. These wind slabs may be sitting on top of weak surface hoar crystals in lower alpine and treeline areas, which would make them easier to trigger Sunday. Cold temperatures and time should reduce the likelihood of triggering these as we head into the work week.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2.5

    A surface hoar layer buried near the end of January is now down 40 to 80 cm and has recently been quite sensitive to triggering. This layer has been the most sensitive right at treeline, but it is thought to extend into the alpine too.

Confidence

Moderate - Uncertainty is due to extremely variable snowpack conditions reported through the region.

Weather Forecast

Brrrr! Arctic air ushers in bitterly cold temperatures with no new snow in sight.

SATURDAY NIGHT: Overnight low temperature around -30 C, light to moderate north wind, trace of snow possible. 

SUNDAY: Clear skies, daytime high temperature around -15 C, light northwest wind, no snow expected.

MONDAY: A few clouds, daytime high temperature around -25 C, light variable wind, no snow expected.

TUESDAY: Clear skies, daytime high temperature around -25 C, light north/northeast wind, no snow expected.

Avalanche Summary

No new avalanche observations to report from Friday.

On Wednesday and Thursday wind slab development was noted in the Kakwa, more details and images here.

On Wednesday there were reports of numerous natural avalanches 20 to 40 cm in depth running at and above treeline. A southwest slope produced a size 3 natural avalanche. These avalanches presumably ran on surface hoar which was producing very touchy conditions. There are some great visuals of this activity in this MIN.

Snowpack Summary

Since Wednesday the north has gotten 16 to 20 cm while the south half of the region has received 25 to 40 cm, with the Renshaw being the big winner.  

This means that there is now 40 to 80 cm of snow resting on buried surface hoar which is most prevalent above 1600 m, it likely reaches into the alpine too, we're just not sure how high it extends.

Below 1600 m this snow is resting on a crust. 

There are presently no deeper concerns in the snowpack.

Terrain and Travel

  • Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
  • Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.

Regions covered