Bulletin d’avalanche

Presidential Range

Mount Washington Avalanche Center
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Danger d’avalanche

Tue
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

It will be possible for large avalanches to occur from the weight of a person on steep, wind-sheltered slopes today. The avalanche problem will be most likely found on east and south aspects between 3000 and 5500 feet in elevation. It will be easiest to trigger an avalanche where softer snow has collected, covering the old, icy snow surface. Finding and traveling on the old, icy snow surface is one way to avoid the avalanche problem today.

Problèmes avalancheux

  • Wind Slabs

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

    Wind slabs that are variable in size and distribution are common throughout east-facing and south-facing avalanche terrain today at the middle and upper elevations. Firm slabs up to 3 feet thick have formed from an increasing northwesterly wind. Expect to find a strong-over-weak slab structure which is sitting on top of a very firm, slick crust. Especially where slabs are softer to the touch, avalanches from the weight of a person are possible. It will be important to investigate the strength of the bond between the new and old snow before committing to a slope. 

    Remember, snow in the starting zones and higher up in the terrain can be more reactive and form larger slabs than snow lower down in the avalanche path or in the runout. Assessing snow low down in an avalanche path is not always representative of what is up higher.

Avalanche Discussion

Larger slabs from Friday’s snow and continued snow showers throughout the day yesterday have combined to form today’s avalanche problem. Over the past few days, wind slabs have increased in sensitivity and grown in size in some areas due to an increase in wind speed and continued transport of snow from fetch areas. Today, harder slabs from prolonged high wind exposure overnight should act stubbornly, but they still have the ability to propagate because of their weak bond to the old, icy snow surface underneath. In isolated, wind-protected areas, expect softer wind slabs to be more reactive to your presence.

Over the weekend, variability in wind slab size, depth, and distribution was clear throughout the forecast area. Some slopes held an obvious slab, while others were scoured down to the old, icy surface. This variability is a limiting factor for the avalanche hazard rating today, however it requires careful decision making for anyone traveling in avalanche terrain. The variability in slab depth means it will be easy to find thin spots where it may be easier to trigger an avalanche. Additionally, areas that are considered “isolated” or “wind-sheltered,” as often referred to in the forecast, are many times the tops of popular ski descents and may be holding the most concerning snow today. Approach each slope with a critical eye today and don’t assume consistency of conditions across the terrain. 

Thanks to everyone for taking the time to submit observations of snow and avalanche conditions, both inside and outside our avalanche forecast area. Please keep them coming.

The Lion Head Summer Trail is closed for the season due to avalanche risk. The Lion Head Winter Route is open.

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