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

You are most likely to trigger an avalanche at middle and upper elevations today as a northwest wind moves recent snow onto easterly aspects. Fresh drifts will be sensitive to your weight and may avalanche naturally on steep slopes. Large avalanches may occur on steep east-facing aspects.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Expect to find sensitive wind slabs building and cross loading onto east-facing aspects this morning that will increase in size throughout the day. With moderate wind speeds, these slabs are likely to be more reactive than we typically find with higher wind speeds. In the steepest terrain, including the headwall of Tuckerman Ravine, it is possible for these slabs to avalanche naturally from their own weight. With roughly 12 inches of new snow available to be transported, developing wind slabs could be two to three feet thick in some locations, enough snow to easily bury a person. 

    The red flags of new snow and wind, coupled with how snow is behaving under your feet, will be more useful than stability tests in assessing this avalanche problem. Visible wind-loading snow at the ridgelines and shooting cracks are an obvious sign you’ve found this avalanche problem.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    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. 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

Wind speeds yesterday were light, resulting in minimal wind slab formation. Careful skiers were treated to 12 inches of storm snow with minimal wind effect by avoiding north-facing slopes. Overnight, northwest wind increased to 30-40 mph, driving snow transport into eastern terrain which will continue throughout the day today. Expect these slabs to be more reactive to a trigger than we often see from strong winds following a winter storm. As denser wind slabs build on a bed of softer wind protected storm snow, a strong-over-weak structure will result. As the slabs build, the weak snow below will be stressed and may fail from the weight of the new snow alone, or from the weight of a person. Wind scouring in upper start zones is also less likely at these wind speeds, allowing slabs to form higher in the ravine gullies. 

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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