Bulletin d’avalanche

Eastside Region

Eastern Sierra Avalanche Center
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Danger d’avalanche

Sun
Alpin
3 · Marqué
Limite forestière
2 · Modéré
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

Significant snow accumulations in the southern part of the zone mean that the avalanche hazard is more elevated in areas south of Mammoth.  Fresh and sensitive wind slabs will be our primary concern near and above treeline.  Loose wet sloughing will also be possible today on solar aspects and at lower elevations. Critical snow and terrain assessment will be essential today.

Problèmes avalancheux

  • Wind Slabs

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

    Yesterday’s storm brought snow accumulation ranging from 0” up to 10” depending on the region. Recent observations suggest the highest storm totals are in areas south of Mammoth and along the Sierra crest.  Strong winds have been largely out of the northeast and concentrated at higher elevations. While winds are expected to drop significantly throughout the day, they will continue at transportable speeds. Expect the size and distribution of fresh wind slabs to be greater in areas with higher snow totals. Large drifts, recent cornice growth, hollow upside-down feeling snow, and uneven snow surfaces are all clues that indicate nearby wind deposits. Do your own localized assessments and be suspect of terrain features that encourage drifting, such as the leeward sides of ridgelines, alpine couloirs, gully features, and cross-loaded depressions.

    Intentionally triggered D1 wind slab avalanche. East aspect, near treeline terrain 8775 ft, Mammoth area. 18 inches thick soft slab broke 50 ft. wide and ran 40 ft. The slab broke on Fist-hard precipitation particles.

    Photo: Clancy Nelson

  • Loose Wet

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

    Temperatures will be significantly warmer today with partly cloudy skies and decreasing winds. Surface moistening and an increased risk of rock fall should be expected on solar aspects and at lower elevations as the sun returns.  Keep an eye out for early warning signs such as sticky and moist surface snow, upside-down feeling snow, and rollerballs & pinwheels. These are clues that may foreshadow larger point-release avalanches. Consequential areas of unstable snow are more likely in areas with higher snow accumulations from yesterday’s storm.  Be wary of your exposure to terrain hazards and be prepared to retreat to more shaded aspects if surface warming reaches concerning levels.

    Multiple small wet loose avlanches on an east aspect at 13,000'. 4/21/23.

  • Loose Dry

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

    In the past 12 hours, mountains in the southern half of the ESAC zone (South of Mammoth) saw moderate accumulations of low-density snow over slick old snow surfaces. On shaded, wind-protected slopes, dry loose avalanches may be a factor today. The terrain where these avalanches are most concerning is steep northerly slopes near and above the treeline that have a long vertical run where sluffing snow can entrain the snow below it, building into a larger avalanche. Timing will be an important consideration for loose snow concerns today. Backcountry enthusiasts will likely be able to observe the transition from loose dry concerns this morning to loose wet concerns this afternoon. Monitor localized accumulations closely and be aware of your exposure to terrain traps below.

    Photo: Steve Mace

Avalanche Discussion

New snow and mild spring weather will be a powerful draw to the backcountry enthusiast today. Don’t let the spring fever lure you into making poor decisions.  The snowpack will be in a state of transition today where loose, cold surface snow will stiffen, becoming more moist as the day progresses.  While you may see loose dry sluffs this morning on cold protected slopes, by this afternoon avalanche concerns will shift around the compass rose to more solar aspects where loose wet avalanches will become increasingly likely. Backcountry enthusiasts will be able to monitor this shift throughout the day.  Keep in mind that the snowpack doesn’t like to see rapid change. Avalanches of concerning size will be more likely as you move south of Mammoth, up in elevation, and as the day progresses.

Régions couvertes