Bulletin d’avalanche

Sea To Sky

Feb 24 – 25, 2020Avalanche Canada
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Archivé · expiré 7 years ago

Danger d’avalanche

Wed
Thu
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Points saillants

Recent snow rests on a weak layer so it may take longer than usual to bond to old surfaces and will likely remain reactive to human traffic. Continue to make conservative terrain choices while storm snow settles and stabilizes.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    1–2

    30-60 cm of recent snow is settling into reactive storm slab over a weak interface consisting of surface facets, surface hoar or sun crusts (aspect/elevation dependent). Storm slabs will be deepest where strong southwest winds have loaded lee terrain features in alpine and exposed treeline areas. A forecast switch in wind direction from south to northwest Sunday will mean wind loading on a variety of aspects.

Confidence

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

Weather Forecast

Sunday night: 5-10 cm new snow. Moderate to strong northwest wind. Freezing level dropping from 1000 m to valley bottom.

Monday: Mix of sun and cloud. Moderate northwest wind. Freezing level 800 m.

Tuesday: 5-10 cm new snow. Light to moderate southwest wind. Freezing level 900 m.

Wednesday: Cloudy. Light to moderate northwest wind. Freezing level 1300 m.

Avalanche Summary

Natural loose dry avalanches to size 1.5 were observed Saturday. Extensive explosive control work produced numerous size 1.5 storm slab and loose dry avalanches. Slabs were touchy, 10-30 cm deep and running far on firm bed surfaces.

Also on Saturday, a deep persistent slab size 3 was observed on a northwest aspect. It was estimated to be 2 days old, failing on basal weak layers and sliding on glacial ice. This has been the first report of an avalanche on these deep weak layers for several weeks.

Snowpack Summary

30-60 cm of recent snow sits over a layer of widespread surface facets, surface hoar in sheltered areas or sun crusts on solar aspects. Recent avalanche activity indicates a poor bond at this interface. In the alpine and exposed treeline, recent snow has been redistributed by strong wind, loading deep deposits into lee features.

Faceted snow and crusts exist near the base of the snowpack in much of the region. This layer is believed to be largely dormant at the moment but appears to be most likely a problem on the eastern side of the region, in alpine terrain, and where there is relatively smooth ground (e.g., glaciers, scree slopes, rock slabs). The first sign of activity in several weeks was reported on Saturday, a size 3 slid on glacial ice on a northwest aspect.

Terrain and Travel

  • Use increased caution at all elevations. Storm snow is forming touchy slabs.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.

Régions couvertes