Boletín de aludes

Central Sierra Nevada

Sierra Avalanche Center
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Peligro de aludes

Wed
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó 4 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

People could still trigger avalanches today in areas where wind-blown snow has piled up near ridges or in more sheltered areas where recent snow rests on top of weak snow. Look for signs of unstable snow, like recent avalanches, blowing snow, and cracks in the surface snow. If these clues exist or there is doubt about the snow's stability, move into gentler terrain.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    Strong E and NE winds have built slabs of wind-drifted snow on SE-S-SW-W-NW-N aspects near and above treeline. While the winds should decrease today, they may remain strong enough to transport snow at times. People could still trigger wind slab avalanches today. On some sunny slopes, sun and warmth on the cold snow may make them easier to trigger.

    Blowing snow, fresh piles of wind-drifted snow, wind-created surface textures, and snow surface cracking can help identify where unstable wind slabs may still exist. Wind slabs could lurk in unusual places due to the NE winds. Traveling in terrain sheltered from the wind can help bypass potentially unstable wind slabs and locate more consistent snow conditions. 

    (1/30/2023)

    Small wind slab failure on a NW facing aspect near treeline on Silver Peak.

    Photo: SAC

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    Cold weather has kept the storm snow soft and loose in wind-sheltered near and below treeline terrain. It has also kept the storm snow from bonding with itself and the snow below it. This recent snow will start to gain strength in today's warmer weather. As it coalesces, it will become more of a slab layer. In areas where the new snow rests on top of surface hoar or graupel, triggering an avalanche that involves the storm snow will remain possible. These would stay small and shallow in places where only 3 to 4 inches of storm snow exists. In the areas where more storm snow fell, larger avalanches could occur. Today's warming may also produce some small wet snow instabilities in the recent snow. 

    Cracking in the storm snow, unstable test results, or reaching into the snow and finding it easy to pull the storm snow away from the snow below it all indicate possible unstable storm slab conditions. If signs of instability or uncertainty about a slope exist, bypass that area and switch to sub-30-degree slopes without steeper terrain above. 

    (1/29/2023)

    An ECT with partial propagation on buried surface hoar. Just lacking a sufficiently cohesive slab. South of Carson Pass, near Charity Valley, CA

    Photo: SAC

Avalanche Discussion

  • Skier-triggered cracking and small wind slab failures occurred on small test slopes loaded by the NE and E winds yesterday. 
  • Some small sluffs of loose dry snow occurred on steep slopes yesterday as the storm snow slid downhill on weak surface hoar. 
  • Buried surface hoar exists under the recent storm snow in some areas. Some places also have graupel at the base of the storm snow. 
  • Widespread wind-affected snow exists in open areas near and above treeline. 
  • Warming temperatures today will change the snow surface, and some wet snow may form, especially on sunny slopes. 

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