Bollettino valanghe

Presidential Range

Mount Washington Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
3 · Marcato
Sotto il limite
Senza grado
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In sintesi

You could trigger a very large avalanche that could bury you, multiple people, and damage trees. These dangerous avalanche conditions can be found on steep north, east, and south-facing slopes at middle elevation. Deep drifts of new snow or cracking underneath your feet are signs that conditions are dangerous. Approach avalanche terrain with caution, perform careful snowpack observations, and use conservative decision-making to mitigate hazards today.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–3

    Large wind slabs that may be sensitive to the weight of a person could be found on steep north, east, and south-facing slopes. MWOBS recorded over 18 hours of 75+ mph west and northwest winds, these winds will likely have scoured upper elevations limiting the size of the avalanche problem you could find there. Middle elevations are the areas of greatest concern today, and where careful snowpack assessment and visual observations will be critical today. These avalanches could be multiple feet thick and have the destructive potential to bury multiple people and destroy trees. 

    Signs of dangerous wind slab conditions will be smooth, rounded and pillow snow slopes, deeper drifts in wind protected areas, shooting cracks under your feet, and recent avalanches. Assessing slab depth will help to understand the size of these newly formed wind slabs and instability tests like hand shears and column tests will help to understand sensitivity. Manage overhead hazard by limiting time underneath large wind slabs. Consider the terrain and potential consequences today as decision makers, these avalanches have the potential to be very large and may not give many, if any warning signs of instability.

Avalanche Discussion

Over 18 hours of 75+ mph winds will have decreased sensitivity in these newly formed wind slabs, pushing well past the window of peak of instability for natural avalanches. Typically this is criteria that fits the definition of a moderate hazard, however today, considering the potential size of very large human triggered avalanches the hazard remains elevated at CONSIDERABLE.

Another thing discussed this morning was that these wind slabs were formed in really cold temperatures, with yesterday averaging 0 F. These cold temperatures may have preserved instabilities of the former wind slabs that had not been released in the previous large cycle earlier this week. Slopes like Central Gully in Huntington showed a large wind slab visible from the road Wednesday evening that formed from the same conditions that produced very large and destructive avalanches in Hillmans and Tuckerman Ravine. The cold temperatures may have preserved the same weak layer that those avalanches failed on, and the new wind slabs formed yesterday may have been enough stress for those to fail and step down. It is also possible that this set up remains and has not yet avalanched and today could be susceptible to human triggers. Due to new coverage it may be hard to tell what has avalanched as the extreme winds often work to scour crown lines, debris, and can reload terrain. 

Looking ahead, we have issued an avalanche watch as a coastal storm will bring significant precipitation with 8-12+ inches of snow forecast to fall during the day tomorrow. Snowfall rates will be heavy with 1-2 inches forecast to fall at times. The heavy precipitation and wind speeds will create dangerous avalanche conditions and our recommendation will be to avoid all avalanche terrain.

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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