Avalanche forecast

Presidential Range

Mount Washington Avalanche Center
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Avalanche danger

Sun
Alpine
4 · High
Treeline
4 · High
Below
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Highlights

Very dangerous avalanche conditions exist. Natural and human-triggered avalanches large enough to bury people are very likely. Some avalanches will be large enough to snap trees or destroy a house and may run far into areas previously considered safe. Traveling in or under avalanche terrain is not recommended.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1.5–3.5

    New snow, driven by strong winds, will create additional, dangerously large and reactive wind slabs on top of existing wind slabs at elevations above 3500 feet. The hardness of these wind slabs may vary depending on aspect and terrain features. In areas sheltered from the wind, these slabs are likely to be softer and may behave more like storm slabs. However, it's important not to overlook the potential for large wind slabs forming at ridgelines above.

    Existing large slabs may slide early in the storm due to the added weight of the new snow. Avalanches initiating within the new snow layer could act as effective triggers for deeper weak layers in the existing snowpack, creating very large avalanches. Large slab avalanches may run further than usual, potentially affecting popular hiking trails such as the Tuckerman Ravine trail past Hermit Lake, the Gulf of Slides Trail, Summer Lion Head Trail, and the Fan of Huntington Ravine.

    The best advice is simple, stay far away from large open steep slopes capable of producing avalanches. Visibility is likely to prevent you from using visual cues that would normally help keep you out of trouble in wind-loaded avalanche terrain.

    Very large avalanche in Tuckerman Ravine 3/20/24

Avalanche Discussion

Things to consider:

  • Stepping Down: Thursday's strong winds have stiffened the snow surface, creating a bridging layer that may temporarily support a person's weight. However, there is a considerable risk that an avalanche in the new snow could break through this layer and entrain the older snow below, resulting in larger and more destructive avalanches. It's important not to assume that the existing snowpack is stable.
  • Natural Avalanches: Avalanches can occur naturally without warning, potentially starting hundreds of feet above you even if conditions seem manageable underfoot.
  • Unsurvivable Avalanches: Avalanches may be so large that companion rescue is not a realistic safety measure.

Weather Key Points:

A strengthening low-pressure system is set to bring a significant winter storm to the forecast area, starting last night and continuing into Saturday. This storm will be characterized by heavy snowfall and moderate to strong winds, which will significantly increase the avalanche danger. 

  • Heavy snowfall is expected with rates of 1 to 2 inches per hour possible early Saturday morning.
  • Snowfall rates may taper somewhat mid-morning Saturday, but another round of heavy snow is expected late Saturday afternoon into the night as colder air moves in.
  • 15 to 20+ inches of snow is forecast. 
  • Southwest winds will shift northwest this evening. 

How did we get here?

Over the past week, several factors have contributed to the current snowpack going into this weekend. 

  • Snowfall: 30 inches of snow has been recorded at upper elevations in the previous 7 days.
  • Wind: Winds have predominantly been from the west at speeds of 30-50 mph, which are perfect for transporting snow into east-facing ravines.
  • Avalanche Activity: This period has seen at least two natural avalanche cycles. Some large paths have already released and slid, while others remain heavily loaded and ready to avalanche. Very large avalanches have occurred in the Gulf of Slides, Tuckerman Ravine and Hillman’s Highway. (Obs1,Obs2,Obs3). Paths that have slid this week now have new slabs formed by recent elevated winds.
  • Temperature: Cold temperatures have limited the settlement of these large slabs.

Field observations conducted on Friday have shown that, despite strong winds on Thursday, instabilities persist in the snowpack. Notably, graupel from last weekend remains in the terrain and may act as a persistent weak layer due to the cold temperatures we've experienced this week. 

Given these conditions, we strongly advise against venturing into avalanche terrain today. The combination of new and wind-loaded snow, existing instabilities, and challenging visibility creates a highly dangerous dynamic avalanche environment. Today is not the day to tempt risk, as the consequences are too great and the hazards are likely to be unmitigable.

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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