Bulletin d’avalanche

Northwest Coastal

Apr 4 – 5, 2017Avalanche Canada
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Archivé · expiré 9 years ago

Danger d’avalanche

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

New snow, wind, warming, and rain will increase the avalanche danger on Tuesday. It's a good time to stick to conservative terrain.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    2–3
    A weak layer from February produced several large human triggered avalanches at the end of March, and may still react in shallow areas. Heavy loads such as a storm slab avalanche or a cornice fall are also possible triggers.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    1–2
    20-40 cm of new snow and wind speeds exceeding 60 km/h will build very touchy storm slabs.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–2
    Rain at lower elevations will cause loose wet avalanches in steep unsupported terrain features.

Confidence

High -

Weather Forecast

TUESDAY NIGHT: 15-25 cm of snow, 60+ km/h south wind, freezing level up to 1200 m.WEDNESDAY: Another 5-15 cm of snow throughout the day, 60 km/h south wind, freezing level around 1000 m.THURSDAY: Linger flurries with another 5-10 cm, moderate southeast wind, freezing level up to 1000 m after an overnight freeze.FRIDAY: Mostly cloudy with isolated flurries, moderate southeast wind, freezing level up to 1000 m after an overnight freeze.

Avalanche Summary

On Monday, two large cornice falls were reported, one of which triggered a size 2.5 persistent slab avalanche on the February weak layer on a northeast aspect at 1600 m. Explosive control north of Stewart produced numerous size 1-2 wind slabs and cornices on north and northwest aspectsOn Wednesday, expect the new storm slabs to be touchy at higher elevations with the ongoing potential for deeper avalanches on the February weak layer.

Snowpack Summary

Strong winds and 20-40 cm of new snow will form fresh storm slabs above 1200 m. At lower elevations, rain will weaken the snow and release loose wet avalanches in steep unsupported terrain features. On shaded aspects above 1300 m, the new snow is burying 20-30 cm of old storm snow. Elsewhere, a mixture of crusts and moist snow surfaces exist from recent melt-freeze cycles. The late February persistent weak layer continues to be a concern for triggering large avalanches. This combination of crust and weak facets is now down 100-150 cm. Recent snowpack tests at the May Creek area found moderate sudden results on the layer on a east aspect around 1200 m. The layer could still be triggered by light loads in shallow weak spots.

Régions couvertes