Bulletin d’avalanche

Mt Hood

Northwest Avalanche Center
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Danger d’avalanche

Fri
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 5 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

A fast-moving storm will bring new snow, strong winds, and rising avalanche danger throughout the day Thursday. Avoid large wind-loaded features and unsupported slopes 35 degrees and steeper. Be especially cautious during periods of heavy snowfall and minimize your exposure to overhead hazard.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2–2.5

    New snow and wind will form fresh and reactive drifts with the most dangerous avalanche conditions developing Thursday afternoon. Existing slabs formed over the past week of heavy snowfall are still healing, and additional loading will not help the situation. Cornices are also a concern and are overbuilt along many ridgelines. If they fall, they could act as huge triggers on slopes below.

    Pay attention to changing conditions throughout the day. Westerly winds up to 50mph will easily transport new and existing low-density snow into thick drifts. Travel cautiously if you transition into wind-affected terrain. Seek out lower-angle or wind-sheltered slopes to reduce your risk.

    (12/28/2021) Obvious wind loading on Pea Gravel Ridge. The west-facing windward aspect is scoured with exposed rock, and the east-facing leeward aspect is fat and loaded. Photo: Andrew Kiefer

  • Storm Slabs

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

    It has been a prolonged period of cold, snowy weather, and the pattern continues Thursday. However, two factors make tomorrow's storm stand out. First, precipitation intensity looks high, with around 1ft new snow expected in just a 12 hour period. Second, the snow will fall at slightly warmer temperatures relative to the past week. This combination will likely create cohesive slabs with a poor bond to cold, old snow surfaces. Be heads up by the time 6in or more new snow accumulates. Look for cracking in the new snow as your travel, and easy or sudden fractures in tests. Seek out small, inconsequential features to assess the new snow before considering larger slopes. When in doubt, default to lower angle terrain.

    (12/25/2021)

    Example photo of a skier-triggered avalanche (size D1) about 1 foot deep in recently fallen snow on Arrowhead Mtn. (5800ft, W) near Stevens Pass. 

    Photo: Stephen Semanski

Avalanche Discussion

Blowing snow and wind loading should be widespread near and above treeline Thursday. Visibility will be poor and avalanche conditions will worsen throughout the day. By afternoon, choose simple, lower-angle terrain and avoid travel in the runout of large avalanche paths.

The 6-7ft of storm snow since 12/21 is settling and stabilizing in wind-sheltered areas. The recent snow has settled to about 4ft, and it is right-side-up and well bonded to the solstice crust. Stability tests targeting the recent snow have not produced concerning results. 

A very large avalanche occurred on 12/23 on the Newton Clark Headwall. Find out more information in this REPORT in the NWAC Avalanche Occurrence Database. Although this very large avalanche is an outlier event, it should give you pause before exposing yourself to large alpine terrain from above or venturing to the upper mountain in the coming days.

Although temperatures are moderating slightly, they remain unseasonably cold. Make sure you are prepared for the conditions and think through the consequences of any accident leading to extended exposure in backcountry terrain. With all the recent snow, watch out for tree wells and keep eyes on your partners. Learn more about deep snow safety HERE.

Régions couvertes