Bollettino valanghe

Presidential Range

Mount Washington Avalanche Center
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Pericolo valanghe

Wed
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

New snow and light winds could make it easy to trigger small avalanches today. Beneath the new snow are areas of older wind-drifted snow, which are less likely to avalanche but are much larger in size. Watch out for quick changes in snow hardness, cracking, or recent avalanches, which are signs of unstable snow.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2.5

    Small wind slabs between 6 inches and 1 foot may develop throughout the day today that are reactive to the weight of a person. Wind slabs varying in depths from 1 - 4 feet deep can be found underneath shallow new snow in steep, alpine terrain on easterly and southeasterly aspects. Expect these slabs to react stubbornly or be unreactive to potential triggers. This avalanche problem could produce large avalanches that are up to D2.5 in size and slide deep into runout paths. Though slabs are thick and firm in some areas, finding a thin spot near the flanks of a slab will make triggering an avalanche easier to do. Knowing where thin spots are from a distance can be impossible.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    A shallow snowpack and very cold temperatures has driven the development of weak faceted crystals of snow at lower elevations in and outside of our forecast area. The addition of new snow and mixed precipitation today as well as recent wind slab formation (which may have developed in isolated areas) may make this problem more sensitive to a trigger. Steep snow slopes on all aspects at lower elevations may fail from the added weight of a skier or climber. Red flags for this problem may include an audible whumpfing you can hear and feel, and shooting cracks. Also keep in mind the consequences of even a small avalanche if you are climbing or skiing in steep, technical terrain.

Avalanche Discussion

3 - 6 inches of new snow falling on light winds may make safely traveling and navigating safely through avalanche terrain more challenging today. New snow will cover evidence of large, existing wind slabs from the weekend’s storm event. Without being able to see the older snow surface underneath the new snow, it will be a roll of the dice between windslab or a scoured, hard old snow surface. Though it may be hard to trigger a larger existing wind slab, their large size, hard debris, and lack of visual identification should be a main topic of conversation in the decision making process today. 

Throughout the day, there is a potential for new wind slabs to form on easterly and southeasterly aspects at mid and upper elevations. There is some uncertainty around the potential for mixed precipitation to be found within this new snow at mid and upper elevations. If this happens, the mixed precipitation may form a breakable crust layer that is difficult to ski or travel in and could increase small, loose avalanche activity. 

We’ve been tracking development of facets at elevations below 3000 feet for the last few weeks. The facets exist, but generally have not been an avalanche problem due the shallow snow pack. Recent observations (Wildcat, Grafton Notch, Great Glen) show that new snow and wind from the February 4th and 5th storm event has added stress to this layer. Today, with the potential for increased weight on the snow pack with snow and mixed precipitation, this trend could continue. Keep this in mind when traveling on slopes steeper than 30 degrees at lower elevations. We’ll continue to watch this over the next few days to see if this weak snow structure is capable of producing an avalanche with some additional snowpack stress, if not we will likely remove Persistent Slab as an avalanche problem.

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

Please help us and your fellow skiers, riders, and climbers by submitting any pertinent or interesting observations to our website.

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