Bulletin d’avalanche

Mt Hood

Feb 12 – 13, 2019Northwest Avalanche Center
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Archivé · expiré 8 years ago

Danger d’avalanche

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

Deep new snow combined with very strong winds and warming has created dangerous avalanche conditions requiring conservative terrain choices Wednesday. Avoid steep slopes greater than 35 degrees, especially higher terrain that received wind deposited snow where you are likely to trigger life-threatening avalanches. Avalanches could be large and run far and fast.

Problèmes avalancheux

  • Wind Slabs

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

    Ridgetop winds have averaged 20-40 mph and gusting to 60 mph over the past two days. 3 feet or more of storm snow combined with these strong winds are building deep slab layers in exposed terrain, with large hard slabs forming above treeline. Any wind-affected snow is likely to be very sensitive to human triggering. Most wind slabs overlie faceted (weak) snow above a firm crust (sliding bed surface), which is a dangerous recipe for slab avalanches. Avoid avalanche terrain and stick to low angle sheltered terrain well away from open slopes above.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1

    Continued snowfall overnight will continue to build unstable slabs that may produce large natural or human-triggered avalanches. A very weak underlying snow structure exists in most areas, consisting of weak snow that may be poorly bonded to a hard crust, especially on any southerly facing terrain. Winds will keep the storm slab problem confined mostly to sheltered terrain. It will be best to avoid steep slopes greater than 35 degrees and seek out wind sheltered terrain Wednesday.

Discussion

Snow and Avalanche Discussion

Since Sunday morning an impressive 3 ft or more of new snow has fallen in the Mt Hood area! The early storm snow fell with cold temperatures and more recent snow with gradual warming and very strong winds Monday night and Tuesday. All this storm snow is sitting on a hard crust and in areas is poorly bonded due to weak faceted crystals that formed on the crust. Widespread natural and controlled avalanches were reported Tuesday at Mt Hood Meadows. There were both soft and hard slab releases with many slides releasing to the crust layer, buried 3-6 ft or more in wind loaded terrain. Storm slabs were also sensitive to human trigger to lower elevations Tuesday, with some slides running fast and far. It will take extra time for these dangerous conditions to stabilize requiring conservative terrain choices. The safest and best conditions exist on lower angled terrain in wind sheltered locations.

Snowpack Discussion

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