Bulletin d’avalanche

Central Sierra Nevada

Sierra Avalanche Center
Voir sur la carte

Danger d’avalanche

Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
Open full map
Périmé — ce bulletin a expiré 6 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

A weak refreeze of the snow surface is expected again today with above freezing overnight temperatures and clear skies.  Loose wet avalanches and cornice fall will be possible as rapid warming occurs.  MODERATE avalanche danger will exist today at all elevations.

Problèmes avalancheux

  • Loose Wet

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

    Clear overnight skies will provide a brief and superficial snow surface refreeze due to radiational cooling.  Overnight low temperatures were in the mid 30's to mid 40's at most locations.  Rapid warming occurring early this morning will melt and break down these surface crusts quickly.  E-SE-S aspects will melt the fastest and could be wet and unsupportable by mid-morning.  SW-W-NW-N-NE aspects will have varied melt rates throughout the day.  Timing will be critical if you want, or need, to travel in avalanche terrain today.  Loose wet avalanches large enough to injure or bury a backcountry user are possible.

    Loose wet avalanches could occur as soon as the snow becomes wet and unsupportable.  Changing aspects may help to avoid deteriorating snow conditions.  Avoid avalanche terrain as the snow becomes wet and deep.

    Photo:  Recent loose wet avalanche on Mt. Tallac, Desolation Wilderness area.

  • Glide Cracks

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

    Cornice fall remains possible throughout the forecast region with a weak overnight refreeze and rapid warming today.  Large cornice blocks could break and slide downslope.  This cornice fall could also release loose wet avalanches or wet slab avalanches as they fall and load the slopes below.

    Avoid areas and slopes below large cornices.  Stay well back from the edges of cornices along ridgelines and avoid any cracks that are along the backside of cornices. 

     

    Photos:  Large cornice chunk from recent cornice fall on Mt. Tallac.  Large cornices on Carson Pass.

Avalanche Discussion

Loose wet avalanches were reported from Mt. Tallac, in the Desolation Wilderness area, yesterday.  A group descending at 12:30pm on E-SE aspects caused numerous loose wet avalanches to run downslope.  Previous large loose wet avalanches and cornice fall was also observed in this area.

Observations from Little Roundtop, Carson Pass area, showed mostly supportable conditions into the midday.  By the early afternoon, snow became unsupportable below 8500'.  Evidence of previous loose wet avalanche activity along with cornice fall was observed in this area.

Snow surface conditions warmed quickly on Relay Peak, in the Mt. Rose area.  E aspects were wet and unsupportable by 9am with some sections of good corn snow found early on S/SW aspects.  Melt freeze crusts of 3-4'' thick became wet and unsupportable quickly yesterday.   

Régions couvertes