Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

The strong April sun is expected to make conditions conducive to wet snow avalanches today on sun exposed slopes across all aspects. Small, unstable slabs may linger in places where wind drifted snow filled in over the past 24 hours, as well as in isolated areas on other slopes. Identify signs of instability and move cautiously around suspect terrain.

 

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Despite the cold start to this morning, full sun is expected to contribute to rapid warming of the snow surface in sun exposed areas across all aspects. Areas around exposed rocks and cliff bands tend to warm faster than surrounding areas. Keep in mind that the sun angle is now high enough to significantly impact northerly aspects.

    Look for signs of snow surface warming, including roller balls and pinwheels. Slopes and flats that received significant sun yesterday likely have a breakable crust on the surface this morning. The change from a breakable crust to a soft wet surface or the presence of roller balls/pinwheels are indications of potentially unstable wet snow.  Consider moving to lower angle slopes if these signs of instability are present.

    Wet loose instability often initiates first around sun exposed rocks and cliffs where the most rapid heating occurs. March 25, ENE aspect on Elephant's Back, Carson Pass area, CA

    Photo: Public

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    1–1.5

    Ridgetop winds made a 180 degree shift from SW to NE early yesterday morning. Small amounts of drifting snow and new shallow, small wind slabs were observed yesterday along some southerly aspect terrain at and above treeline. Wind speeds over the past 24 hours were strongest yesterday morning and again early this morning. Snow surface warming today may make any slab instability easier to trigger on sun exposed slopes.

    Recent avalanches, test slope failures, and snow surface cracking may indicate that unstable slabs exist in your area. Identify areas where recently wind drifted snow has filled in. These frequently include slopes below or adjacent to wind drifts, cornice features, in gullies, and on open slopes. Often the snow on the upper portions of these slopes have snow surface texture indicative of wind loading. Once you identify signs of potential instability and the associated slopes of concern, move around these slopes with caution.

    With the below average air temperatures following the recent storm, it is not impossible that isolated slab instability leftover from the recent storm could linger across colder N-NE aspect terrain. Take this into consideration as well, especially for travel in complex terrain. 

    Some recently wind loaded areas may have some hybrid wet snow/slab characteristics today, similar to what was observed on this slope back on March 29.

    Photo: Sierra Avalanche Center

Avalanche Discussion

Two skier triggered slab avalanches were reported yesterday in steep, NE aspect terrain. One was a size D1 that occurred near 8,500' on Peak 9,268' (West Shore Tahoe area) and carried a skier approx 300 vertical feet through a cliff area. The skier was not buried but sustained serious injury. The second avalanche was a size D2 slab/wet snow hybrid that occurred mid-slope (approx 7,600' to 7,800') on Flagpole Peak (Echo Summit area). The triggering skier was not caught or carried.

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