Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

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3 · Marcato
Limite del bosco
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Sotto il limite
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Non aggiornato — questo bollettino è scaduto 9 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

As sun and warm temperatures cause rapid warming today, the avalanche danger will increase to CONSIDERABLE once last night's refreeze melts. Large human-triggered loose wet avalanches are likely today if people venture onto steep slopes where wet snow exists. Natural loose wet avalanches are possible. Some wet slab avalanches may also be possible today. The warming will weaken any lingering wind slabs keeping human-triggered wind slab avalanches possible today as well. Avoid slopes where wet snow or wind slabs exist.

Problemi valanghivi

  • Loose Wet

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

    Strong April sunshine and warm temperatures will lead to rapid warming of the snow today. This rapid warming will quickly melt through last night's refreeze and weaken the snow. Human-triggered loose wet avalanche activity will become likely on any slopes that receive sunshine today. Some natural loose wet activity will be possible as well. These loose wet avalanches could entrain all of the new snow and could involve enough snow to pose problems for backcountry travelers. The largest loose wet instabilities will exist on the slopes where the most new snow exists and where the most warming occurs.

    Avoid slopes where signs of rapid warming like sticky wet surface snow, roller balls, pinwheels, or other signs of wet snow exist. Once the sun hits the slopes today, the snow will quickly become unstable and less fun to recreate on. Seek out shaded sheltered slopes where the snow remains cold and non-wind-affected for better and safer recreation.

  • Wind Slabs

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

    Fragile wind slabs and cornices may still linger on or above wind-loaded slopes. Today's rapid warming could also weaken the bonds holding these wind slabs and cornices in place and make them more fragile and easier to trigger as the day warms up. Wind slabs could exist on wind-loaded N-NE-E aspects as well as on cross-loaded NW and SE aspects. Any wind slab avalanches that occur today could involve enough snow to bury or injure a person. The largest and most fragile wind slabs will exist in near and above treeline terrain in areas where the most new snow has accumulated on slopes that receive sunshine.

    Clues like cornices above slopes, drifted snow, ripples in the snow surface, and other wind created textures can help identify where fragile wind slabs may exist. Use this information to avoid the wind slabs and to find sheltered non-wind-affected snow to travel on.

  • Persistent Slabs

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

    Loose wet snow instabilities should comprise most of the wet snow issues today, but some wet slab avalanches may become possible as the day warms up. Wet slab avalanche problems could develop in sun-exposed areas on any slopes where more than a few inches of new snow exists. Any wet slab avalanches that occur today could involve enough snow to bury or injure a person.

Avalanche Discussion

Yesterday observations from Hidden Peak found 8 to 10 inches of new snow at the upper elevations and 1 to 2 inches of new snow below 7300 ft. This new snow rested on top of deep wet snow. Ski cuts on test slopes at all elevations triggered large pinwheels and ski-width-wide loose wet avalanches that entrained whatever new snow existed. Near the summit of Hidden Peak where wind-loading had formed wind slabs, small cornice pieces dropped on the slopes also triggered similar loose wet instabilities. 

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