Lawinenlagebericht

Central Sierra Nevada

Sierra Avalanche Center
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Lawinengefahr

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

Buried surface hoar beneath our recent storm snow has been found in the forecast region creating a persistent slab avalanche problem. Wind slab and loose wet avalanche problems will also be possible today.  Multiple persistent slab and wind slab avalanches were reported yesterday.  MODERATE avalanche danger will exist with human triggered avalanches expected.

Lawinenprobleme

  • Deep Persistent Slabs

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

    Surface hoar that formed earlier this week has been buried by our recent storm snow.  This buried surface hoar now sits under around 1 foot of storm snow in wind protected areas and up to 2 to 3 feet deep in wind loaded areas.  The low density storm snow will continue to settle, gain strength and become more cohesive.  Multiple avalanches were reported yesterday with wide propagation, remote triggering, and whumpfing sounds on this buried surface hoar weak layer.  Continued human triggered avalanche activity is expected today.

    This persistent slab problem exists on NW-N-NE aspects at all elevations.  The buried surface hoar will exist in open areas and not densely tree covered terrain.  Avalanches could continue to fail mid slope with very wide propagation.  Manage your aspects and slope angles carefully.  Remote triggering is very possible, so avoid connected terrain to larger avalanche paths. 

      

  • Wind Slabs

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

    Wind slab avalanches continue to occur post storm.  Some of these wind slab avalanches could be failing on top of buried surface hoar or one of the many layers of graupel that was deposited during the storm.  Winds shifted briefly from the SW to the NE yesterday and remained light throughout the day.  They are forecasted to shift to the W today and increase to moderate to strong speed by this afternoon.  Additional wind transport of snow could start as winds increase.  Wind slab avalanches remain possible in near and above treeline areas.

    Look for built out cornices, wind pillows, and steep wind loaded terrain.  These avalanches have been propagating wider than normal.  Avoid areas below large cornices and wind loaded slopes.  Manage terrain to reduce your risk.

      

  • Loose Wet

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

    Partly sunny skies today with intense March sunshine will create wet snow on solar aspects throughout the day.  Areas with more mid to high level cloud cover will have reduced loose wet activity.  Loose wet avalanches will become possible as the snow surface becomes wet and loses strength.  These loose wet avalanches could involve some or all of the recent storm snow. 

Avalanche Discussion

Multiple persistent slab avalanches failing on buried surface hoar were reported from the Blue Lakes area on Carson Pass.  Some of these avalanches had very wide propagation, were remotely triggered, and failed mid slope. 

Wind slab avalanches were reported from Silver Peak (Pole Creek area) and Frog Lake Cliff (Donner Summit area) yesterday.  4 other similar wind slab avalanches were observed near Silver Peak that were thought to have occurred on Wednesday.

Observations on Mt. Tallac at the site of a previous avalanche from Wednesday reveled buried surface hoar as the failure layer.  Whumpfing sounds were observed in the area along with snowpack tests that showed propagation likely on this weak layer.

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