Lawinenlagebericht

Central Sierra Nevada

Sierra Avalanche Center
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Lawinengefahr

Thu
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Kernpunkte

New snow today along with strong winds will create areas of wind drifted snow.  In addition, warming temperatures, rising snow levels, and rain at lower elevations, will lead to wet snow instabilities.  These avalanche concerns will increase throughout the day with the avalanche danger expected to further rise tomorrow as a larger, more powerful storm enters our area. 

 

Lawinenprobleme

  • Wind Slabs

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

    New snow with strong to gale force SW winds will create new wind slabs in near and above treeline areas.  These new wind slabs have started forming overnight with additional new snow available for wind transport and will continue throughout the day.  At lower elevations, these wind slabs may be weakened by warming temperatures and rain today.  At higher elevations, these wind slabs will continue to build and become weaker with more snow and continued winds into tonight.   

    Look for signs of wind slab development today.  Blowing snow, cornice formation, wind pillows, and snow surface cracking in wind loaded areas, are all signs that wind slabs are present.  Use caution around large cornices and slopes below steep wind loaded terrain.

  • Loose Wet

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

    Warming temperatures, rising snow levels, and rain up to 7500', are expected this afternoon.  Rain on snow will deteriorate bonds quickly and weaken the upper snowpack including any new snow that has fallen overnight and today.  Most of these wet snow instabilities are expected to be in the form of roller balls, but some could entrain more snow and be larger in size involving all of the recent storm snow and some previous unconsolidated surface snow.

    A "time it early" approach could help limit this avalanche problem today.  Getting out early and being out of the backcountry before the forecasted warmer temperatures and rising snow levels could help avoid most of these issues.  Warming temperatures and rain on snow could quickly increase the avalanche hazard and result in unstable snow conditions.

         

Avalanche Discussion

* We've been monitoring surface hoar around the forecast area as a potential future weak layer if it persists to burial.  The recent strong to gale force SW winds have destroyed or knocked over much of this surface hoar in wind exposed areas over the past few days.  Mountain inversions, with warmer air at the higher elevations and colder air near the valley bottoms, have also likely limited surface hoar development above around 7000'.  Recent observations show intact surface hoar with the potential for burial by new snow limited to shaded, wind protected, lower elevations areas below around 7000'.  Forecasted warming today with increasing rain levels are expected to further reduce this issue.    

 

 

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