Avalanche forecast

Presidential Range

Mount Washington Avalanche Center
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Avalanche danger

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

Heavy snowfall and wind will increase avalanche danger on all aspects of the compass. It may be easy to trigger an avalanche in new and wind drifted snow, especially later in the afternoon and evening. On steep east-facing and south-facing slopes, triggering a deeper, more destructive avalanche that is hidden by new snow is possible. Poor visibility may make stability assessments and route finding very challenging.

Avalanche problems

  • Persistent Slabs

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

    On east-facing and south-facing aspects at middle and upper elevations, old slabs between 1 - 3 feet in depth are becoming buried by new snow. A generally poor snowpack structure with two distinct persistent weak layers and propagation potential could become a problem with increased weight of new snow or the weight of a person. This avalanche problem is likely stubborn to react to a trigger, but carries serious consequences if an avalanche does occur. If new snow or wind slabs have covered the old snow surface, this problem will be impossible to identify from a safe distance. Digging in the snow to assess layers and instability can give a general idea of the conditions but remember it is only a snapshot that may not be representative of the whole picture.

    These slabs may be reactive to the weight of a single person, especially at thin spots in the slab, and have the ability to propagate across a large slope. Check out this observation from a human-triggered avalanche Saturday in Tuckerman Ravine. A video of the incident filmed by a member of the public can be found in the incident report. Areas of similar snow are now buried under new wind slabs and storm snow.

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–1.5

    8 - 10 inches of new snow falling today and tonight on light and moderate southeast winds will likely blanket the terrain with a layer of soft storm snow. This new snow may create small soft slab avalanches, even if it has not yet formed a stiffer, deeper wind slab. On north and west-facing slopes, expect storm snow to form slightly stiffer slabs and be more sensitive to the weight of a person. 

    Later tonight and early tomorrow morning, shifting winds will begin to transport new snow to east and south-facing slopes and form new wind slabs that are increasingly sensitive to the weight of a person. These new wind slabs are likely to form in the same or similar locations where persistent slabs are hidden underneath new snow. A smaller wind slab avalanche has the potential to cause a deeper, much more destructive avalanche multiple feet deep. 

    Watch for blowing snow as a sign or rapid loading and that wind slabs are forming. Visibility may make it challenging to safely assess where new slabs have formed. Careful, well-planned route finding is critical while also looking out for stiff, hollow-sounding snow and shooting cracks as signs that you have found a new unstable wind slab.

Avalanche Discussion

Accurately assessing avalanche conditions today will challenge any backcountry traveler. Constant assessment of wind speed and direction will help to identify the new wind slab problem. If lower-than-forecast wind speeds occur, expect wind slabs to be slower to build and expect to find small storm slab conditions. 

Storm snow and new wind slabs have hidden areas of older slabs which are harboring multiple instabilities. Notably, a thin crust and thin layer of facets from radiation recrystallization on February 21st and 22nd can be found generally 1 - 2 feet below the snow surface. Below that, a melt/freeze crust dating back to February 17th can be found up to 3 feet or more below the surface of the snow. These layers have the ability to cause avalanches moving forward, especially with significant snow forecast for today and wind loading from the northwest to follow the storm. 

Persistent avalanche problems are not often seen here in the Presidentials. In this case, a unique setup of weak layer formation, cold temperatures, lighter-than-usual winds, and consistent snowfall, has allowed for this to happen. Persistent slab avalanches are very dangerous (even if the likelihood of triggering them is lower) since the instability is hidden well below the surface of the snowpack. Determining slope stability can also be dangerous since there is no sure way to judge the stability of a slope from a distance. The instability may also be stubborn. For instance, 10 people could ski a slope, which could appear to be stable, but all it takes is for the 11th person to find an invisible thin spot in the slab for it to trigger. Avoidance is the most effective way to mitigate and avoid a persistent avalanche problem. 

 

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. 

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