Avalanche forecast

Presidential Range

Mount Washington Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Wind and new snow have combined and created dangerous avalanche conditions on steep, east and south aspects above 3000ft in elevation. In these areas, large avalanches could happen naturally or from the weight of a person. Sound decision making, knowledge, and safe travel techniques are necessary for safe travel in and around avalanche terrain today.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2.5

    Wind slabs varying in depths from 1 - 6 feet deep can be found in steep, alpine terrain on easterly and southeasterly aspects. This avalanche problem could produce large avalanches that are D2 or D2.5 in size and slide deep into runout paths. Expect these slabs to be sensitive to any disturbances or travel on them. 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

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    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 a wind slab (which may have developed in isolated areas) may make this problem even 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 whumping you can hear and feel, and cracking of the snowpack around you. Also keep in mind the consequences of even a small avalanche if you are climbing or skiing in steep technical terrain.

Avalanche Discussion

Yesterday’s weather brought higher wind speeds to the Presidential Range sooner than was forecast. This resulted in impressive wind loading rates that lasted the entire day. Natural avalanches were observed in multiple areas yesterday. Main Gully of Gulf of Slides slid naturally at least twice at a size of D2, avalanche debris was observed in Hillman’s Highway, and avalanche debris was observed on the Lion Head Summer Route slide paths. With limited visibility, it is expected that multiple other slopes also saw natural avalanches, but we will not be able to confirm this until there is better visibility today. Even though avalanches occurred, expect avalanche paths to have become re-loaded with wind-deposited snow and ready for another trigger.

Even with winds subsiding overnight, slowing or stopping active wind loading, don’t rule out the possibility of more natural avalanches today as the snowpack continues to adjust to the additional load and quick change in snow conditions. Some uncertainty still revolves around how much the wind affected the snow at higher elevations. There is a chance to see conditions more along the lines of a MODERATE rating in these areas, but we are not yet able to confirm this. Remember, wind slab in the starting zone of an avalanche path is going to act differently than the snow in other locations. This means that instability test results or snow pit profiles elsewhere are likely not representative of the snow and avalanche problem in the start zones.  

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 the 12 inches of new snow have not only added stress to the weak snowpack, it also creates the potential to be an avalanche problem with the increased volume of snow. Keep this in mind when traveling on slopes steeper than 30 degrees at lower elevations. The trouble with persistent slab avalanche problems is..they persist. However, if conditions are such that they are not producing avalanches then they may be best thought of as dormant. We’ll watch this over the next few days to see if this weak snow structure is capable of producing an avalanche, if not we’ll 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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