Bollettino valanghe

Presidential Range

Mount Washington Avalanche Center
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Pericolo valanghe

Wed
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

During the day today, it will be possible for large avalanches to occur from the weight of a person on steep, wind-sheltered slopes on east and south aspects. Look out for areas of softer, smooth, wind-drifted snow which has collected on top of an old, icy snow surface. 

This evening, new snow and wind may increase the avalanche hazard on north through east aspects enough for natural avalanches to be possible and for new snow drifts to be very sensitive to the weight of a person.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Firm wind slabs resting on an old, hard snow surface are common throughout the forecast area at middle and upper elevations on northeast through south aspects. In general, existing wind slabs have a strong-over-weak character. Slab depth will vary between 1 - 4 feet, directly correlated with exposure to the wind. Expect slabs in wind-protected and sheltered terrain to be softer, deeper, and more reactive to the weight of a skier or climber. It will be important to investigate the strength of the bond between the new and old snow before committing to a slope. 

    This evening, new snow may build wind slabs on north-facing through east-facing terrain. With several inches of snow, new slabs could be over a foot in depth, increasing the load on older wind slabs, or forming on the old, icy bed surface. This variability and potential for larger, more destructive avalanches could warrant a CONSIDERABLE rating for the onset of the evening hours.

Avalanche Discussion

Over the past few days, wind slabs have grown in size in some areas due to an increase in wind speed and continued transport of snow from fetch areas. Today, harder slabs from prolonged high wind exposure overnight should act stubbornly, but they still have the ability to propagate because of their weak bond to the old, icy snow surface underneath. In isolated, wind-protected areas, expect softer wind slabs to be more reactive to your presence.

Today’s avalanche problem requires careful decision making for anyone traveling in avalanche terrain. The variability in slab depth means it will be possible to find thin spots where it may be easier to trigger an avalanche. Additionally, areas that are considered “isolated” or “wind-sheltered,” as often referred to in the forecast, are many times the tops of popular ski descents and may be holding the most concerning snow today. Approach each slope with a critical eye today and don’t assume consistency of conditions across the terrain. 

If significant amounts of new snow fall tonight, expect an increase in the likelihood of natural avalanches for the rating to tip from MODERATE to CONSIDERABLE as we move into tomorrow. In the case of several inches of new snow, there is a potential for both smaller avalanches propagating on the old melt/freeze crust surface, as well as propagation on top of existing wind slabs with a chance for this failure to step down onto the buried melt/freeze crust, making it a much larger and more destructive avalanche. Careful evaluation of the weather changes and loading patterns will be necessary to confirm or deny this hazard change.  

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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