Avalanche forecast

North Rockies

Mar 7 – 9, 2021Avalanche Canada
View on map
Archived · expired 6 years ago

Avalanche danger

Tue
Wed
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
Open full map

Highlights

 Wind slabs are the main concern. Deeper layers in shallow snowpack areas in eastern parts of the region are still a concern and are trickier to manage. 

Avalanche problems

  • Wind Slabs

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

    The recent winds have created wind slabs across exposed leeward and crossloaded terrain.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–3

    The persistent slab problem appears to have been put to rest in deep snowpack areas in the west of the region, but on the eastern slopes (e.g. Kakwa) this is less certain. The most likely triggers are surface avalanches stepping down, cornice fall, or the weight of a machine or a person hitting a thin-spot.

Confidence

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

Weather Forecast

Saturday Night: Mainly cloudy with isolated flurries, accumulation 1-3 cm, moderate southwest wind, alpine temperature -5 C, freezing level at valley bottom.

Sunday: Mainly cloudy with scattered flurries, accumulation 1-5 cm, moderate to strong west and southwest wind, alpine temperature -4 C, freezing level 1200 m.

Monday: Mainly cloudy with scattered flurries, accumulation 1-5 cm, moderate southwest wind, alpine temperature -3 C, freezing level 1300 m.

Tuesday: Mix of sun and cloud, moderate to strong west wind, alpine temperature -3 C, freezing level 1300 m.

Avalanche Summary

The warm temperatures this week triggered loose wet avalanches on solar (south throug west) aspects. Strong winds triggered wind slabs naturally up to size 2 and explosive controlled avalanche (near Pine Pass) up to size 3. 

See this MIN post near Mc Bride on Friday which sums up recent avalanche observations nicely.

Snowpack Summary

Strong south to west winds in exposed areas have scoured some slopes and built windslabs on others. Freezing levels reached treeline Thursday and Friday with +3 C at Renshaw, +8 C in Kakwa on the east side of the divide. It has cooled slightly since so you will likely find a dusting of new snow on the surface or a crust treeline and below.

There was a range of accumulated new snow totals from last weekend: somewhere around 90 cm in Pine Pass (the deepest), down to 30 or 40 cm in Kakwa. The key point is there's recent loose snow at higher elevations available for wind transport. 

About a metre of snow covers a weak layer of facets (and potentially surface hoar) from mid February and a slightly deeper, widespread persistent weak layer from late January/early February that consists of surface hoar. It is most prevalent around treeline elevations, but likely reaches into the alpine and in openings below treeline too. These layers are both significantly shallower in the east of the region.

Terrain and Travel

  • Avoid freshly wind loaded terrain features.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

Regions covered