Bollettino valanghe

Eastside Region

Eastern Sierra Avalanche Center
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Pericolo valanghe

Thu
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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In sintesi

Expect dangerous avalanche conditions. Though natural avalanches will become less likely throughout the day, you can trigger large to very large slabs of recent and drifted snow in steep terrain. Deeply buried weak layers could result in giant avalanches hitting the runouts of large paths. Don’t let your guard down as the storm clears.

Problemi valanghivi

  • Wind Slabs

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

    Wind loading could continue into the late morning. Dense slabs of drifted snow built up quickly yesterday and overnight. Touchy cornices developed during the storm. Wind deposits will take time to stabilize. Though natural wind slab avalanches will be less likely throughout the day, large human-triggered slides are likely below ridgelines and in cross-loaded gullies. If you trigger a wind slab today, it could step down to older snow and the resulting avalanche could be much more dangerous than expected. Avoid steep leeward terrain where avalanches could be big enough to bury or kill you. The runouts of avalanche paths with wind-loaded start zones pose significant overhead hazards today.

    Large Wind Slab avalanche in the June Lake area. 2/14/13.

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2.5–4

    A persistent weak layer of faceted snow was buried in late February. Several deep slab avalanches released on this layer in the 48 hours prior to yesterday’s powerful storm. A questionable snowpack structure has been rapidly loaded by intense snowfall and wind into the early hours of this morning. Don’t expect this extremely dangerous problem to stabilize as quickly as wind or storm slabs. Potential deep slab triggers may include other avalanches or cornice fall. Deep Slabs can propagate widely, connecting multiple start zones and terrain features. With good coverage in the tracks of avalanche paths at all elevations, these avalanches could reach maximum runouts and impact areas like mature forests and flat terrain usually considered safe zones. Avoidance is the best way to manage an uncertain and unsurvivable hazard. 

    (3/13/2023) Photo: Jeff Montgomery

  • Storm Slabs

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

    Snowfall decreased early this morning and the recent snow will become less sensitive throughout the day. Soft, cohesive slabs of recent snow and sluffs fanning out from a point will be possible in steep sheltered terrain. Sunshine midday could trigger wet snow on solar aspects. Convexities and confined terrain features like chutes are most concerning. Terrain traps like cliffs, creek beds, or deep tree wells would increase the consequences of triggering an avalanche. 

    (3/14/2023)

    Intentionally triggered storm slab avalanche 

Avalanche Discussion

Multiple avalanches were reported during yesterday’s storm. Forecasters triggered storm slabs, wind slabs, and sluffs to size 1 breaking at the new/old snow interface. Natural storm slabs and wet snow avalanches slid on snowbanks in Mammoth. Intense snowfall and extreme winds continued overnight. As snowfall and winds die down this morning natural avalanches will become less likely, with the exception of possible wet snow instabilities as the midday sun hits the new snow. 

 In the past 72 hours, several explosive-triggered and step-down deep slab avalanches indicate that the deep persistent slab problem was still sensitive to larger triggers. The expected size for deep slabs has increased and there is potential to reach historic runouts in some paths. Cornice fall or relatively smaller avalanches could be all that is needed to trigger one of these monsters.

Most avalanche accidents occur at considerable danger on the first good weather day after a major storm. Be extra cautious and conservative. Remember that resources are stretched thin as highway and county officials continue to manage the new snow. If you do venture out today, be considerate of snow removal efforts. Blocking snow drifts, travel routes, and snow piles makes it impossible for road crews to finish the job.

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