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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Veraltet — dieser Lagebericht ist 13 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

MODERATE avalanche danger exists on slopes 35 degrees and steeper on all aspects in near and above treeline terrain due to new wind slabs, the formation of loose wet snow, and unlikely but not impossible deep persistent slabs. MODERATE avalanche danger also exists below treeline on slopes 35 degrees and steeper on the SE-S-SW-W aspects due to the formation of loose wet snow.

Lawinenprobleme

  • Wind Slabs

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

    Strong southwest winds combined with some snow still available for transport on the upper elevation windward aspects, means that new wind slabs could form on leeward slopes today. These wind slabs should remain smaller than those that formed during the storm, but human triggering of them will be possible today. The wind loaded NW-N-NE-E-SE aspects in near and above treeline terrain will hold the most fragile wind slabs. Even though it is unlikely it is not impossible that failure of these wind slabs could add enough weight to the snowpack to cause the resulting avalanches to step down to deeper weaknesses in the snowpack.

  • Loose Wet

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

    Warmer overnight temperatures, daytime warming, and sunshine could cause enough melting in the upper snowpack for some wet snow instabilities to form again today on the E-SE-S-SW-W aspects below 8500 ft. These should remain limited to surface instabilities like roller balls, pin wheels, and wet loose avalanches. Wet slabs should remain unlikely, but not impossible today.

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    3

    Weak layers of well developed facets and depth hoar remain buried deep in the snowpack on near and below treeline NW-N-NE aspects above 9,000 ft. The strong thick layer of new snow above these weak layers has made breaking these weak layers difficult and deep persistent slab avalanche activity has become unlikely. However, it is not impossible for the right trigger in the right place to still release one of these slabs. Areas where a shallower snowpack exists (like where the whumphing occurred on Tamarack yesterday) or where trigger points like rocks are closer to the surface could allow humans to still trigger these slides. Since near and below treeline areas above 9,000 ft. only represent a small portion of the forecast area this problem remains isolated in distribution.

Avalanche Discussion

Observations from near Round Top on Carson Pass, Talking Mountain on Echo Summit, and Tamarack Peak in the Mt. Rose area all showed a thick layer of storm snow ranging from 3 to 6 ft in depth. The storm snow in all three of these locations showed signs of continued settlement and consolidation. On Talking Mountain and near Round Top some less dense layers still remained within the storm snow in the top 3 to 4 ft of the snowpack, but data and observations did not reveal any signs of instability associated with those storm snow weakness. As the winds picked up yesterday they started transporting snow at the upper elevations and adding more wind loading to leeward slopes on Talking Mountain and in the Round Top area.

In all three of these areas yesterday, weak snow still exists at the bottom of the snowpack at the upper elevations. On Round Top, on Talking Mountain, and in most places on Tamarack data and observations indicated that while this weakness remains, it would be very difficult to trigger. However, human triggered whumphing did occur in one spot on Tamarack Peak where a shallower (2-3ft in depth) snowpack existed. 

Some wet loose avalanche activity did occur yesterday on the SE-S aspect of Jake's Peak, and some skier triggered wet loose sluffs occurred on steep, sun-exposed, S facing test slopes between 7600 and 8200 ft. on Talking Mountain.

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