Bulletin d’avalanche

North Rockies

Feb 26 – 27, 2022Avalanche Canada
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Archivé · expiré 5 years ago

Danger d’avalanche

Mon
Tue
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Points saillants

If you see any blowing snow, seek out sheltered terrain where the snow will not be wind affected and riding will be at its best.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Strong upcoming winds will have the potential to reload previously scoured slopes and build reactive wind slabs on immediate lee features of north-facing alpine slopes. Uncertainty remains about how much low-density snow will get transported and how well the developing slabs will bond to old surfaces.

    Older and stiffer wind slabs still exist on various aspects in any exposed terrain and around ridgelines, as the past winds blew from various directions, creating slabs in less common locations.  

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

The ridge of high pressure will keep the region dry and cold, with the potential for lingering valley clouds. The next round of snow is expected late Saturday night as a shift in the weather pattern will occur.

Friday night: Clear skies. Alpine temperatures around -8 C. Light to moderate southwesterly winds.

Saturday: Cloudy with isolated flurries. Freezing level rising to 1000 m. Alpine temperatures around -6 C. Strong southwesterly winds up to 60 km/h.

Sunday: Snow 5-10 cm. Freezing level rising to 1200 m. Alpine temperatures around -4 C. Strong southerly winds up to 60 km/h.

Monday: Snow 5-10 cm. Freezing level rising to 1400 m. Alpine temperatures around -2 C. Strong southerly winds up to 60 km/h.

Avalanche Summary

Wind slabs are still showing signs of instability on isolated features as human-triggered and natural avalanches have been reported thought out the region. 

Snowmobilers were able to trigger numerous small wind slabs (size 1) on convex lee features around Mt West on Thursday. Check out our field team's MIN report for photos and details. A very large natural avalanche (size 2.5) was also observed around Bear Pass on a north-facing alpine slope.

Earlier this week, shifting winds have redistributed the storm snow into wind slabs and several natural avalanches occurred. Evidence from the last storm is still visible around Kakwa, as numerous large natural storm slab avalanches were reported from treeline elevations.

Snowpack Summary

Recent cold temperatures and northerly winds have modified and transported the last storm snow (20-100 cm), creating heavily wind-affected surfaces in exposed areas and wind slabs in lee areas. This recent snow overlies a widespread crust (1 to 20 cm thick) which is found on all aspects and elevations.

Below the crust, 10-40 cm of more settled snow exists above the late January weak layer. This layer consists of weak faceted snow, a melt-freeze crust, and surface hoar crystals in isolated sheltered areas at treeline and below. In most areas, this layer is bridged by the thick crust above it. It is currently considered dormant, but could become active later this season. 

The lower snowpack is generally strong and well-bonded. The base of the snowpack is expected to be weak and faceted in shallow, rocky slopes east of the divide.

Terrain and Travel

  • Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Closely monitor how the new snow is bonding to the crust.
  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.

Régions couvertes