Bulletin d’avalanche

Northwest Coastal

Feb 9 – 10, 2016Avalanche Canada
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Archivé · expiré 11 years ago

Danger d’avalanche

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

There is a great deal of uncertainty regarding how the snowpack will recover from recent storm loading and very warm temperatures. I would manage this uncertainty with conservative terrain selection.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–6
    Recent storm loading, solar radiation and skyrocketing freezing levels have increased the likelihood of waking-up deep and destructive persistent weak layers. Cornice falls may also trigger a persistent slab avalanche.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–4
    Recently formed storm slabs may remain sensitive to human triggering on Wednesday, especially in the north of the region where recent accumulations were the greatest and more recent temperatures remained cooler.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–3
    Elevated freezing levels on Wednesday may promote ongoing loose wet avalanche activity. Loose wet avalanches may also step down to deeper, more destructive layers.

Confidence

Moderate - Due to the number of field observations on Tuesday

Weather Forecast

A series of relatively weak Pacific moisture systems will impact the region over the forecast period. On Wednesday and Friday expect 5-10cm of moist snow each day while only trace amounts are expected on Thursday. Freezing levels should drop gradually from 1800m on Wednesday to about 1000m by Friday. Ridgetop winds should remain mainly moderate to strong from the southwest.

Avalanche Summary

A widespread natural avalanche cycle to size 3 took place on Monday in response to recent storm loading and then rain. Avalanche types observed were loose wet, wet slabs, storm slabs and persistent slabs. I'm sure more of the same was observed on Tuesday with rising freezing levels and localized solar radiation. Cooling with help reduce avalanche activity; however, the forecast cooling trend is so gradual it's tough to say exactly when or to what extent.

Snowpack Summary

On Sunday a warm, wet and windy storm added mass and reactivity to recently formed storm slabs. 24 hour snow totals were around 40cm in the Terrace area with closer to 70cm falling in the mountains around Stewart. Rain on Monday, and then rising freezing levels and solar radiation on Tuesday have likely left most surfaces moist or wet. This warming has had a significant destabilizing effect on the snowpack. The January 9th surface hoar/facet layer is down 70-200 cm and remains a concern, especially with heavy and/or thin-spot triggers. Around the same depth you may also find a surface hoar/facet interface from around New Years. There continues to be a lot of uncertainty regarding the reactivity and distribution of this destructive persistent avalanche problem; however, warm temperatures have increased the likelihood of triggering these layers where they still exist. A very conservative approach to mountain travel is still required.

Régions couvertes