Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

Mon
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Areas of unstable surface wet snow are expected to form quickly this morning in response to rapid warming. Natural cornice fall is also a concern. The best bet for today is to time travel in avalanche terrain during the early morning hours and to consider avoiding avalanche terrain from late morning onwards.

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1–2

    Air temperature inversion conditions are giving most slopes a head start on melting this morning. Many upper elevation areas are already at 40 degrees at sunrise. Last night's snow surface refreeze was fully dependent on radiational cooling of the snowpack under clear skis. A weak to decent snow surface refreeze is expected to have occurred on open slopes. Areas under forest canopy may not have refrozen at all. 

    It's April and the sun angles are now high enough to create wet snow on all aspects. Long open slopes with sustained slope angles will have the potential to create the largest wet loose avalanches. In areas where rollerballs or pinwheels are occurring or the upper snowpack is wet and unsupportable, consider moving to slopes less steep than about 35 degrees in slope angle to reduce the risk of becoming caught in a wet loose avalanche.

    (4/8/2023)

    Wet loose avalanche, trigger type unreported, E aspect terrain near 9,700' on Tamarack Peak, Mount Rose area, NV.

    Photo: Public

  • Cornices

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–2.5

    There is an increased likelihood of a natural cornice fall cycle today and tomorrow. Some of the cornices out there near treeline and above treeline on N-NE-E aspects range in size from very large to massive. Falling blocks of very dense snow will have some destructive potential.

    The exact moment that a cornice fall will occur is nearly impossible to predict and is often larger than expected. Nearly everyone involved in a cornice fall incident while on a ridgetop is caught by surprise when the cornice breaks off much further back from the edge than expected. Stay well back from cornice areas on ridgetops by staying close to exposed rocks or trees. Consider avoiding travel on slopes underneath cornices.

    (3/31/2023)

    It won't take much for some of these cornices to collapse. Ward Canyon, CA

    Photo: Public

Avalanche Discussion

  • A colder start to the day yesterday delayed most wet loose avalanche occurrences until the midday to afternoon hours. A much warmer start this morning and increased heating will allow for wet snow instability to occur much earlier today.
  • Recent new snow is expected to have assimilated with the older melt-freeze crust below it on E-SE-S-SW-W aspects in areas that received three inches or less of new snowfall on Friday. Areas that were wind loaded or received more snow will take longer for the recent new snow to transition to uniform melt-freeze in the upper snowpack.

Regioni coperte