Lawinenlagebericht

Central Sierra Nevada

Sierra Avalanche Center
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Lawinengefahr

Thu
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

Avalanche activity continues to decrease. However, triggering an avalanche may remain possible on an isolated steep slope where weak snow lurks below the storm snow or where wind-blown snow has piled up near ridges, gullies, and other exposed terrain. If you see signs of unstable snow or have doubts about a slope, move on to a different option. Travel plans that use simple terrain and create safety margins may help reduce the consequences of an avalanche. 

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–2.5

    The snowpack continues to gain strength, and obvious signs of instability like cracking, whumpfing, and collapsing have become less prevalent. Avalanche activity has also decreased, with the last known persistent slab avalanche occurring on Sunday or Monday. Some tests still indicate that the old snow buried under the recent storm snow remains weak on northerly aspects, especially in areas where a shallower snowpack exists. 

    Most people will not see signs of unstable snow today, nor will they trigger avalanches. Still, triggering a persistent slab may remain possible in some isolated areas. These spots are more likely to hide in complex terrain like couloirs, cliffy/rocky areas, or places with multiple overlapping avalanche paths where more variability exists. If one of these avalanches does occur, it would be surprising, large, and consequential. Choosing simpler terrain may help reduce the consequences, while lower-angle terrain could help avoid the problem.

    (12/15/2024)

    80’ wide 18” to 30” crown.  Snowmobile triggered avalanche on Sunday, Dec 15.  Relay Peak, Mt. Rose area.

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Winds have decreased over the last 24 hours and blowing snow remained limited yesterday. Much of the wind-blown snow that piled up on the leeward sides of ridges, gullies, and other wind-exposed terrain features has bonded with the snow below it. Triggering a wind slab avalanche should be more difficult today, but some unstable wind slabs may still linger in more heavily wind-loaded areas. 

    Recent avalanches, cracking in wind-blown snow, cornices above a slope, piles of drifted snow, and wind features on the snow surface can help indicate where unstable wind slabs may still linger. Identify the wind-loaded areas and move around them carefully. Using sheltered terrain can help increase the potential to find softer, non-wind-affected snow. 

    (12/17/2024) Small wind slab triggered by cornice collapse.

Avalanche Discussion

Over the last several days, observations have revealed a widespread persistent slab and wind slab avalanche cycle that occurred during the weekend. In addition to the avalanche cycle and snow during the storm, strong winds have left wind-sculpted snow surfaces across the forecast area. To cap it off, rain up to about 8300 ft on Monday deposited a rain crust on many slopes. Expect variable snow surface conditions when traveling in the backcountry.

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