Bulletin d’avalanche

Northwest Coastal

Jan 4 – 5, 2015Avalanche Canada
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Archivé · expiré 12 years ago

Danger d’avalanche

Tue
Wed
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Points saillants

Strong winds have probably redistributed snow and created wind slabs in a variety of places. Make conservative terrain choices and stay tuned to signs of instability. 

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–4
    Strong outflow winds are a common theme throughout the region. Wind slabs could be especially deep and touchy in southern areas where the strong winds coincided with heavy snowfall. 

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    1–6
    There are a couple buried persistent weak layers in the upper and mid snowpack, primarily in northern areas like Bear Pass and Ninginsaw Pass.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–3
    Southern areas near Terrace and Kitimat received ~30-45 cm of snow by Sunday afternoon. There is potential for storm slabs to form in sheltered areas, or the new snow might just react at loose dry sluffs in steep terrain.

Confidence

Fair - Due to the number of field observations

Weather Forecast

Synopsis: We should see a brief lull in the weather on Monday before the arrival of another strong frontal system late in the day. There could be a few breaks Monday morning followed by increasing cloud and snow in the evening. Overnight Monday and through Tuesday we could see 20-40 cm of snow. Winds increase once again to strong from the S-SW. The freezing level stays at valley bottom on Monday and Tuesday with treeline temperatures around -10. Snow and winds should gradually taper off on Wednesday. An above freezing layer might also form between 1000 and 2000 m.

Avalanche Summary

Several natural and explosive triggered wind slabs up to size 2 were reported on Saturday. Most of these were fresh wind slabs up to 40 cm deep from steep north-facing terrain near treeline. Wind slabs will probably remain sensitive to human triggers on Monday.

Snowpack Summary

Conditions are highly variable throughout the region. Southern sections near Terrace received around 30 cm of new snow while Bear Pass and Ninginsaw didn't see any new snow on Saturday night. Strong winds are one common theme in all areas though. Ridge winds have been cranking from the SE stripping windward slopes bare and probably forming hard or dense wind slabs in lee and cross-loaded areas. A buried surface hoar layer, down 25-35 cm, may be more prevalent in northern sections like Bear Pass and Ninginsaw Pass. The mid December crust can be found down around 40 to 80 cm and is sandwiched with facets and surface hoar. The November crust, down 70 to 175 cm, is gaining strength but is still reactive in some test profiles. The deeper snowpack weaknesses could 'wake up' with heavy loading from new snow and wind.

Régions couvertes