Bulletin d’avalanche

North Rockies

Jan 28 – 29, 2022Avalanche Canada
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Archivé · expiré 5 years ago

Danger d’avalanche

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

Lingering wind slabs remain the primary concern with ongoing strong winds at higher elevations. Wind slabs are most likely to be triggered in steep, unsupported, and/or convex terrain features.

Problèmes avalancheux

  • Wind Slabs

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

    Recent strong winds have formed slabs in exposed high elevation terrain. Wind slabs have been most reactive where they overlie a thin crust. Expect these lingering wind slabs to remain reactive to human triggering on steep, convex and/or unsupported terrain features. Continued slab development is possible with the ongoing strong winds where there is still loose surface snow available for wind transport. 

Confidence

Moderate - Uncertainty is due to the extreme variability of wind effect on the snowpack.

Weather Forecast

The ridge of high pressure is expected to break down late Friday before a relatively weak storm system reaches the region Friday night bringing light snowfall for the weekend. The eastern slopes may see some warm air aloft on Friday with the alpine seeing temperatures slightly above freezing. 

Thursday Night: Mainly clear, moderate to strong SW wind, treeline temperature around -8 °C.

Friday: Increasing cloud cover, moderate to strong SW wind, treeline high around -4 °C.

Saturday: Light snowfall 3-6 cm, moderate to strong SW wind, treeline high around -3 °C.

Saturday night and Sunday: Snowfall 5-15 cm, moderate to strong SW-W wind, treeline high around -2 °C.

Avalanche Summary

On Wednesday, a size 2.5 wet slab was reported in the south of the region which was likely solar triggered on Monday or Tuesday. On Tuesday, explosives triggering numerous wind slabs up to size 3 in the south of the region. Some of these were failing down to the bedrock in extreme terrain features. A natural size 2 cornice-triggered wind slab was observed north of McBride. 

Snowpack Summary

The snow surface is highly wind affected in exposed terrain and wind slabs are lingering in leeward features. On steep solar aspects and at lower elevations, a melt-freeze crust may be found on the surface. In sheltered areas at treeline and below, a spotty layer of surface hoar has been reported in the south of the region. 

A thin crust may be found under the last week's snow down 20-30 cm, which was the main sliding surface for the wind slab cycle last weekend. Another crust is found down around 70 cm but has not shown recent reactivity. The lower snowpack is generally strong and bonded, with one or multiple crusts near the ground. We suspect the lower snowpack could be weak in shallow, rocky, wind-affected slopes east of the divide.

Terrain and Travel

  • Be careful as you transition into wind affected terrain.
  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Seek out sheltered terrain where new snow hasn't been wind-affected.

Régions couvertes