Bollettino valanghe

Olympics

Northwest Avalanche Center
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Pericolo valanghe

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

In sintesi

Sustained moderate winds will effectively transport new and low-density old snow into thicker and more reactive deposits. Look for increasingly reactive deposits as you ascend and anticipate the lens-shaped deposits below freshly corniced ridgelines and cross-loaded wind-lips where they may reside. Avoid lee slopes steeper than 35 degrees unless slabs have yet to form in your area.

Problemi valanghivi

  • Wind Slabs

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

    We're expecting another 5-7" of snow along with nearly 24 hours of moderate wind transport. This will effectively transport the new snow (and some lower-density older snow) near ridgelines and quite significantly at upper elevations. By the time the storm eases tomorrow afternoon, average snow depths will be 1.5-2 ft above the Solstice Crust. Wind deposits will be thicker (2-4 ft above the crust) and more resistant. Shooting cracks, heavier or denser feeling snow, actively blowing snow, and fresh sharp cornices are signs alerting you to the problem. If you encounter any of these, avoid lee slopes steeper than 35 degrees.

    If warming starts to consolidate the upper snowpack, there is a chance that a storm slab could develop. Test slopes can help you evaluate this problem if the snow begins consolidating.

    (12/26/2024)

    Small storm slab, stubborn to ski tests.

    Photo: ONP Rangers

Avalanche Discussion

ONP rangers reported excellent riding and few signs of instability on Thursday and Friday. Less than an inch of that recent snow fell within the last 24 hours. 16" of gradually settling lower-density snow has yet to form a slab and is well bonded to the 1 cm thick Solstice Crust.  Much of the wind during the Christmas-Boxing Day storm redistributed higher-density snow, forming gargoyles as winds shifted directions multiple times.  In many cases the winds redistributed some of this snow well downslope, depositing it into forests. We don't have any concerns below the Solstice Crust, but the 12/7 crust (also 1 cm thick) is easily identifiable above melt forms. Check out the snow profile in the gallery.

The avalanche danger will increase Friday night and Saturday due to an expected 5-7" of new snow and sustained moderate winds. There's also a chance of rain at lower elevations. If it does rain in your area, rollerballs and wet loose avalanches could be easily triggered naturally or by humans. Rain on cold snow is a good time to reduce your exposure to all slopes steeper than 35 degrees.

Rideable snow now extends down to around 4400 ft. At these lower elevations, the shallow coverage limits the slab hazard, but consider the impact of even a small avalanche around terrain traps such as creeks, and gullies. Open creeks, downed logs, brush, and thin coverage make for slow going and many hazards are now barely submerged.

Regioni coperte