Bulletin d’avalanche

Central Sierra Nevada

Sierra Avalanche Center
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Danger d’avalanche

Mon
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Another wet storm will enter our area with high elevation snow, rain, and strong winds.  Slabs of wind blown snow will form in gully features, below ridges, and in open terrain.  Sloughs of new snow could slide downhill on existing firm snow surfaces.  Dangerous avalanche conditions will exist today as more snow and wind impact our forecast region.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Wind slabs are expected to form today in near and above treeline areas.  Southwest winds have increased into this morning with ridgetop winds expected to be well in excess of 100mph today.  Wind slabs will form above the rain/snow line, which could be at higher elevations early this morning before dropping quickly down to 7000'.  As this storm intensifies, more heavy snow will be available for wind transport and wind slab development. 

    Look for blowing snow, new cornice formation, and wind pillows as clues to where these wind slabs are forming.  Move around areas of concern and avoid steep wind loaded slopes and areas below large corinces. 

    (12/28/2024)

    Recent wet wind slab avalanche  on Red Lake Peak, Carson Pass area.

    Photo: Public

  • Loose Dry

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    Recent rain has been observed up to 10,000' throughout the forecast area yesterday.  A variety of rain soaked snow to firmer rain crust will exist on the old snow surface.  Generally, bonding is expected to be good between the new storm snow and the old snow surface as we move from warmer to colder temperatures.  As additional snowfall accumulates, there could be some issues on these firmer crusts or within the storm snow as snowfall rates increase.  Dry loose sloughing will be possible in wind protected below and near treeline areas.  This would involve the new storm snow in steeper terrain.  Most of these would be expected to be small in size, but could have increased consequences above terrain traps.  If temperatures fluctuate or if snow levels stay higher than forecasted, this problem could switch over to encompass wet snow instabilities.   

Avalanche Discussion

Over the past several days, incremental loading of deeper, faceted weak layers that linger above 8,000' to 8,500' in the eastern and southern portions of the forecast area has occurred. Thus far, these lingering weak layers appear to have handled the increasing load. These layers include the Dec 12 pwl and basal facets near the ground that both exist where a shallower and weaker snowpack has continued to persist.  That said, if you happen to trigger an isolated snowpack collapse or whumpf sound today, it's best to avoid NW-N-NE aspect avalanche terrain in the immediate area.

Régions couvertes