Lawinenlagebericht

Central Sierra Nevada

Sierra Avalanche Center
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Lawinengefahr

Tue
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
Open full map
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Kernpunkte

Triggering an avalanche remains possible today. Watch out for areas where wind-blown snow has piled up on open slopes near ridges, gullies, and below cornices. Weak snow may still linger on steep slopes in cold, sheltered areas. If you see signs of unstable snow, move to terrain not steep enough for snow to slide downhill.

The avalanche danger will increase tomorrow as a winter storm impacts the area. 

Lawinenprobleme

  • Wind Slabs

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

    Wind slabs still linger on NW-N-NE-E-SE facing slopes where wind-blown snow has piled up below ridges, in gullies, and on open slopes. Some data showed improvement in how wind slabs bonded to the snow below them. Other data, including a wider-than-expected skier-triggered wind slab on a test slope, indicated that triggering a wind slab avalanche remains possible. Wind slabs may still break wider than expected. As the wind increases today, blowing snow could add to the existing wind slabs.

    Recent avalanches, blowing snow, cracking in wind-blown snow, wind-created surface textures, and cornices above a slope can help determine where wind slabs may exist. Recreating in more sheltered areas without signs of wind-loading can help avoid wind slabs, but you will still have to deal with possible lingering weakness in the upper snowpack mentioned below.

    (3/26/2023)

    Skier-triggered wind slab failure on a test slope near Meiss Ridge at Carson Pass.

    Photo: SAC

  • Persistent Slabs

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

    Unseasonably cold weather has allowed weaknesses in the upper snowpack, including graupel layers and lingering storm snow weaknesses, to persist longer than usual, especially on steep NW-N-NE aspects. The cold has also made it hard for the recent snow to bond to the firm surfaces and rain crusts below it. While yesterday was the first day that no new slab avalanches were reported on these layers, ski cuts on a steep N-facing test slope still caused the recent storm snow to slide off the firm snow below it. This sluffing indicates weak bonding between the cold snow and those old firm surfaces. Avalanche activity on these weaknesses should continue to decrease today, but triggering a soft slab avalanche will remain possible, especially on steep terrain with trigger points like convex rollovers. 

    Recent avalanches, unstable snowpit test results, snow surface cracking, snowpack collapse, or whumpfing can help identify unstable snow. Still, patches of unstable snow may exist in seemingly stable areas, and starting an avalanche could be the first sign of lingering instability. If you see any signs of instability or have any doubt about a slope, move to lower-angle, non-avalanche terrain that is not connected to steeper slopes. 

    (3/26/2023)

    Ski cuts on a sheltered N-facing test slope that had previously avalanched caused last night's snow to sluff off the firm old snow surface on Incline Lake Peak.

    Photo: SAC

Avalanche Discussion

  • Ski cuts above a test slope on Carson Pass yesterday triggered a wider-than-expected wind slab failure in the test slope. Another test slope in that area did not break as wide. In the Incline Lake Peak area, ski cuts and tests on wind-loaded test slopes did not produce signs of instability. 
  • Ski cuts on a sheltered N-facing test slope that had previously avalanched caused yesterday's fresh snow to sluff off the firm snow below it on Incline Lake Peak. 
  • While some small rollerballs or pinwheels may form on sunny slopes today, unseasonably cold weather and increased cloud cover this afternoon should prevent widespread wet snow from forming despite the intense spring sun. Sun crusts may exist on sun-exposed E-SE-S-SW-W aspects.
  • No new surface hoar related avalanches have been reported since Monday, and tests targeting this layer indicate that it has gone dormant.
  • The layers in the upper snowpack have started adjusting to the current load, but an additional load tomorrow may reactivate some of these weaknesses.

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