Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Shifting winds have been strong enough at times to blow and drift snow into cohesive slabs in a variety of areas near ridgetops.  Strong sunshine affecting the snow surface will allow for some surface wet snow instabilities to form on slopes with direct sun exposure.  Use caution in areas where recent blowing snow has deposited as well as on steep sunny slopes as daytime warming occurs.

Problemi valanghivi

  • Wind Slabs

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

    Ridgetop winds have continued to shift back and forth between SW and NE over the last couple of days.  Plenty of recent new snow has remained available along the ridgetops for wind transport. Unstable slabs of wind drifted snow remain possible on all aspects in near and above treeline areas.  Expect to encounter a patchwork of wind-scoured and drifted in wind slab areas on all aspects and potentially adjacent to one another.

    Look for blowing snow, drifted snow, and any snow surface clues that can help inform your group where wind slabs have formed or are forming.  Snow surface cracking while traveling through wind drifted areas indicates cohesion in the wind slab.  Make travel plans that move cautiously around steep wind loaded terrain and areas below large cornices.

  • Loose Wet

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

    The sun angle is getting higher and incoming solar radiation is continuing to increase as we move closer to spring. Despite the cooler air temperatures today,  snow surface warming from solar radiation will allow surface wet snow to form on E-SE-S-SW-W aspects as the day progresses.  Areas that intensify the solar radiation such as around rocks and gully features will be the first locations to show rapid warming and wet snow development.  Most wet loose instabilities are expected to be in the mid to lower elevation range, with higher elevations remaining colder with increased winds.

    Roller balls and pinwheels off of rocks, trees, and travelers' tracks will be indications of developing wet snow instability.  In addition to the concerns for today, this avalanche problem is expected to become increasingly widespread over the next few days as air temperatures continue to warm.

Avalanche Discussion

  • Near-surface faceting that occurred during the 38 day Jan/Feb dry spell created weak snow in the upper portion of the snowpack on some wind sheltered NW-N-NE aspects. The recent storm buried this weak layer under 1 to 1.5 feet of storm snow.  Over the past couple of days, the recent storm snow has settled and become more of a cohesive slab. One very isolated whumph with a crack going down to this weak layer was reported yesterday from N aspect below treeline terrain at 7,100' near Brockway Summit. Snowpit tests pointing towards instability have occurred only in very isolated areas post storm. No avalanches have been reported on this weak layer at this time.  On a regional scale, this near surface facet weak layer is very isolated in distribution with avalanches unlikely.  With that said, it is not impossible for a very isolated avalanche to occur on this weak layer in near to below treeline NW-N-NE aspect terrain with all the right ingredients.

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