Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

Tue
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 8 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Heavy rain and high elevation snow continue with lower snow levels and the potential for larger avalanches to occur today.  Slabs of wind drifted snow will form in open areas and wet snow avalanches may also be an issue if temperatures and snow levels change throughout the day.  Early season conditions exist with collision hazards due to our shallow snowpack.

Problemi valanghivi

  • Wind Slabs

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

    Seek out wind protected and less steep terrain today if travelling in the backcountry.  Blowing snow, cornice development, and building wind pillows will be signs of where wind slabs will exist.  Identify where problematic areas may be located in the terrain and make a plan to move around any areas of concern.  

    Wind slabs will form below ridges, in gully features, and in open areas as more snow is available for wind transport with continuing gale force Southwest winds.  Where wind slabs form on top of old weak faceted snow, potential exists for larger avalanches to break down into older weaker snow in the snowpack.  These slabs could exist in the most wind loaded locations and also in more wind protected locations where dense heavy new snow exists over weaker older snow.  A significant load of rain and heavy wet snow has been put on the snowpack at higher elevations and could result in avalanches where this older weak snow exists.

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    If temperatures rise today with increasing snow levels, wet loose avalanches could occur.  Rain on new snow or wet snow formation could lead to instabilities in the surface snow.  Move away from steep slopes if wet surface snow develops in your area.

Avalanche Discussion

Even with the new snow, we have a very limited amount of terrain available for over the snow recreation throughout the forecast region.  Collision hazards with rocks, bushes, stumps, down trees, and open water continue to exist with our shallow high elevation snowpack.  

We had an early start to our winter with snow and rain in October through mid-November.  After a 3+ week dry spell in late November into December, the upper snowpack became weak, faceted, sugary snow.  Widespread snow loss occurred with warm temperatures and high elevation rain that followed leaving a 1-2' snowpack above 8500-9000' on mostly northerly aspects.  More recent rains have made the weak faceted snow in the upper snowpack wet and the layers have been gaining strength at elevations below 9000'.  Above 9000', a more complex picture exists where older snow from Nov-early Dec is located.  Some areas of weak faceted snow have been found with other areas seeing some strength gains from the warmer temperatures and rain.  Due to our limited terrain available with snow, the same areas that folks will be going to recreate will be the same places where this weak snow potentially exists.  Large storm events in the past have shown us that a weak layer does not have to be that weak when we get a large storm event like we have now.

Regioni coperte