Avalanche forecast

Presidential Range

Mount Washington Avalanche Center
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Avalanche danger

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

New snow and changing winds will create dangerous avalanche conditions on all aspects of the compass. Large avalanches that have the ability to bury multiple people are a possibility in all avalanche terrain at upper and middle elevations. New snow and blowing snow may make safety assessments and route finding difficult.

Avalanche problems

  • Wind Slabs

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

    New wind slabs 1 - 3 feet thick will have the opportunity to form today on west-facing aspects from 8 - 12 inches of new snow and wind. These new slabs may be sensitive to the weight of a single person and may also avalanche naturally. They will have the destructive potential to bury multiple people. Watch for the snow surface to become denser and deeper from blowing snow to confirm this avalanche problem.

    Older wind slabs from recent storms are still remaining on east-facing and south-facing slopes. These older slabs are generally 1 - 3 feet in depth and will be hidden by new snow today. These slabs may be reactive to a human trigger and have the potential to create a very large avalanche. Wind slabs on these aspects will be difficult or impossible to assess from a safe distance.

    Overnight, winds will shift from the north and eventually from the northwest by morning. If this shift and speed increase happens earlier than forecast, expect large and sensitive wind slabs to build on east-facing and south-facing slopes. When this shift happens, very large, destructive natural avalanches are likely in the Eastern Ravines of Mount Washington.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1

    New snow falling on lighter winds, especially in the morning, may create point-release, loose avalanches on all aspects today. Even though smaller in size than the wind slab avalanche problem, these may still be big enough to bury a person. These are most likely to be encountered in very steep terrain and also on rocky terrain around cliffs in lower elevation terrain.

Avalanche Discussion

Expect avalanche danger to continue to increase significantly over the next 36 hours. While new snow falling on easterly winds will widen the distribution of the wind slab avalanche problem today, this problem will refocus tomorrow back to east-facing and south-facing slopes. Once this wind shift and speed increase occurs (most likely early tomorrow morning), there is a high likelihood of a large, destructive avalanche cycle in Mount Washington’s eastern ravines. 

Over the past 1 - 2 weeks, multiple avalanche cycles have helped expand the size and connectivity of avalanche paths in the Presidential Range. As new storms continue to roll in, avalanches will have the opportunity to be more destructive and run farther into runout zones than we have seen in the past 2 years. Keep this in mind when selecting travel routes and leave a margin for error. 

Field teams took time to investigate the prevalence and changes of deeper persistent layers in the snowpack yesterday. In observation locations, persistent layers were still identifiable in some areas but have had the opportunity to gain strength over the past week. Warm temperatures and sun yesterday were certainly an aid in this process of settlement and bonding. Little to no propagation potential was observed from these previous layers of concern. Over multiple storm cycles, layers of concern have also been “flushed out” of many areas. Given these observations, and the significance of the upcoming wind slab avalanche cycle, the persistent problem has been removed from the forecast. It is not impossible that an upcoming wind slab avalanche steps down into a deeper weak layer. We expect these deeper persistent layers to become completely benign once we have many hours of 100 mph winds beginning tomorrow night.

The Lion Head Summer Trail is CLOSED due to increased avalanche hazard. The Lion Head Winter Route is OPEN and the most direct route to the Mount Washington Summit from Pinkham Notch.

OBSERVATIONS: Please consider submitting an observation of what you are seeing in your travels. Submitting an observation hones your skills, informs other users, and improves our forecasts. 

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