Avalanche forecast

Presidential Range

Mount Washington Avalanche Center
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Avalanche danger

Tue
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Triggering a small avalanche today in new, wind-drifted snow may be easy. Also, triggering a deeper, larger avalanche on east-facing and south-facing slopes is less likely, but could have deadly consequences. Identifying the larger avalanche problem will be hard or impossible today since it may be covered in new snow. Stick to slopes less than 30 degrees in steepness or travel on hard, textured snow surfaces without overhead hazard to avoid the avalanche hazard.

Avalanche problems

  • Wind Slabs

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

    The 3.5 inches of snow recorded at Hermit Lake in combination with moderate and strong northwest winds have created reactive wind slabs on east-facing and south-facing slopes in steep terrain. These slabs are likely to be between 5 -10 inches in depth and soft, but may be very sensitive to the weight of a single person. Additionally, triggering a new wind slab has the potential of “stepping down” into a deeper layer of instability (see Persistent Slab Problem below).  Look for areas of soft, smooth, and rounded-looking snow to identify where these new slabs could be found. Look out for stiff, hollow-sounding snow and shooting cracks as signs that you have found a new unstable wind slab.

  • Persistent Slabs

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

    On east-facing and south-facing aspects at middle and upper elevations, old wind 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 in the next several days with additional new snow and wind. This avalanche problem is likely stubborn to react to a trigger, but carries serious consequences if an avalanche does occur. If new wind slabs have covered the old snow surface, this problem will be impossible to identify from a safe distance. The only sure way to manage this avalanche problem is to avoid avalanche terrain on the listed aspects. 

    These slabs have proven to 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 this observation. Areas of similar snow are now buried under new wind slabs.

Avalanche Discussion

Assessing avalanche conditions today will challenge any backcountry traveler. 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 Tuesday and strong wind loading to follow the storm. Over the next several days, expect to see an increasing danger trend in east and south-facing avalanche terrain. 

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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