Bollettino valanghe

Eastside Region

Eastern Sierra Avalanche Center
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Pericolo valanghe

Sat
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
4 · Forte
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In sintesi

Heavy snowfall and strong winds are creating very dangerous avalanche conditions. Large natural avalanches are expected. Buried weak layers will add to the size and sensitivity of the hazard today. You could easily trigger slabs large enough to kill you from unexpected places that you may typically consider safe storm-day riding. Traveling in and under avalanche terrain is not recommended.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    2–3

    Snowfall and strong winds continue today. You will find dense, deep, rippled wind deposits on the leeward side of ridgelines, in gullies, and in steep forest clearings. These will be larger near and above treeline and will likely break naturally across start zones. Don’t be surprised to find fresh drifts at lower elevations and further down slopes than normal. Poor visibility will make identifying large drifts difficult. Avoid travel on or below steep, open slopes, and be skeptical of sheltered areas with wind-loaded avalanche paths above you. 

  • Storm Slabs

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

    Heavy snowfall rates of up to 2 inches per hour are forecasted today. Storm instabilities, both slabs, and sluffs, will be sensitive in steep wind-sheltered terrain. Convexities and confined terrain features deserve particular caution. Even small avalanches can be dangerous above terrain traps like cliffs or creek beds. 

    (12/30/2022)

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2–3

    Well-developed facets and facet crust combos exist in the upper snowpack. Storm slabs and wind slabs could step down to buried weak layers creating larger, more destructive avalanches. You can trigger avalanches breaking on old snow from below and from terrain you may typically think of as safe. This is a dangerous problem that’s difficult to assess and predict. Avoidance is the best way to manage your uncertainty. 

    (2/20/2023)

    Crown profile of a wind slab avalanche that stepped down into older layers of faceted snow sometime around 2/14/23.

Avalanche Discussion

Triggered avalanches to size 1 were reported yesterday morning. Folks wisely avoided whiteout conditions and frigid temperatures. The resulting lack of observations is a source of forecaster uncertainty. Regardless, heavy snowfall and strong winds are forecasted across the entire region and down to the lowest elevations through Saturday morning rapidly loading a poor snowpack structure. 

Before new snowfall began on the 21st, occasional, isolated avalanches stepped down to weak faceted layers on north and east aspects. Propagating snowpack tests indicated that these layers could be a source of instability. Uncertainty about the problem stemmed from the spotty nature of the slab overlying this structure. It was not yet cohesive or widespread enough to connect features with the concerning old snow. That’s likely changed. Overlapping avalanche concerns, deteriorating conditions, and a complex upper snowpack will prove tricky to navigate. Poor visibility and cold wind chills will complicate your hazard assessments and any potential rescue scenario. Sometimes it's best to just grab a cup of coffee and watch it snow.

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