Avalanche forecast

Presidential Range

Mount Washington Avalanche Center
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Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Areas of newly formed wind-drifted slabs have developed on steep terrain in the middle and upper elevations. These slabs are sensitive to human triggering and may fail into older subsurface layers of the snowpack in a step-down manner, creating a larger avalanche. Avoid areas where wind transported snow is apparent.

Avalanche problems

  • Wind Slabs

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

    Yesterday afternoon and into this morning we received around 5.4 inches of new snow, with 0.46 inches of SWE, on the summit of Mount Washington. Consistently strong winds from the west and northwest have moved snow from the fetch of the upper snowfields down lower into steep gullies and ravines. Drifted slabs of wind transported snow have formed that could be 1 to 2 feet thick in the upper elevation starting zones. Some of these slabs could be reactive or even touchy in their sensitivity to human triggering.

    It is possible to see evidence of natural avalanches in and below steep ski terrain this morning. It is even more likely that lingering slabs of consolidated wind-transported snow still reside above you in the starting zones and the tract of popular ski runs. Older drifted slabs, from earlier in the week, may become reactive with new snow loading them to the threshold of failure. Step down avalanches are a primary concern when we get repeated storms in succession and no time for proper settlement between them. 

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Dry snow in the middle and lower elevations could prove to be an avalanche problem in locations where slopes are over 35 degrees in steepness. Slick bed surfaces are common under new snow that has fallen since a week ago. Areas protected from the wind will have collected the most snow, offer the best skiing, and therefore draw skiers into them where this avalanche problem resides. You don't need to be in a large avalanche to sustain injuries.

Avalanche Discussion

The combination of new snow and wind has us at Considerable for today’s avalanche hazard rating. Newly formed slabs of wind drifted snow lie over slabs that have formed earlier in the week. It could be difficult to determine new from old slabs, so avoiding them both is a safer alternative. Sometimes a distinction can be made after examining their hardness and reactivity to human triggering. This means observing, digging, and testing to perform your own stability results. Although quick and hasty test pits done lower on a slope do not always translate to what you will find higher on steep slopes.

Observations from the past few days reveal enough sensitivity remains in wind created slabs to propagate cracks across the surface layers of snow. During storm events we focus on wind intensity and direction foremost, but consider when the wind is calm and snow is lightly falling vertically. During slack winds snow will collect in places undisturbed. As increased winds resume it can harden just the surface of the new snow leaving dry unconsolidated snow beneath. A more firm “wind-skin” can develop on the surface, grow thicker and more dense, leaving dry and softer snow below as the new weak layer of concern.

Our highly variable snowpack and ski conditions means there is uncertainty wrapped into each avalanche forecast that is posted. As you climb into avalanche prone terrain today consider the outcome of a worse-case-scenario unfolding around you and those in your proximity. Are you prepared? Do you have the right equipment to save someone, or do all the people in your group have the equipment to rescue you?

Thanks to everyone for taking the time to submit observations of snow and avalanche conditions, both inside and outside our avalanche forecast area. Please keep them coming.

The Lion Head Summer Trail is now closed for the season due to avalanche risk. The Lion Head Winter Route is open.

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