Boletín de aludes

Eastside Region

Eastern Sierra Avalanche Center
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Peligro de aludes

Tue
Alta montaña
4 · Fuerte
Límite del bosque
4 · Fuerte
Bajo el límite
3 · Notable
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Desactualizado: este boletín caducó 3 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Very dangerous avalanche conditions exist this morning where the most new snow has fallen, especially around Mammoth. Traveling on and below wind-loaded terrain is not recommended. New snow could be sensitive to human triggers and could shed as wet snow avalanches as the storm clears. Avalanches breaking in new and drifted snow could step down to deeply buried weak layers resulting in a much larger slide. Conservative decision-making will be essential for safe travel, even outside of the Mammoth area today. 

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Very Likely
    Tamaño
    2–3

    Wind loading could continue into the late morning. Touchy slabs of drifted snow developed quickly yesterday and overnight. They will be bigger and more dangerous as you gain elevation, and where the most new snow has fallen: around Mammoth, and near the Crest. Wind deposits will take time to stabilize as the storm clears. Though natural wind slab avalanches may become less likely throughout the day, large human-triggered slides are likely below ridgelines and in cross-loaded gullies. Blowing snow and cornice development will point to the most dangerous slopes. Shooting cracks in dense snow are red flags. Traveling in steep leeward terrain and the runouts of avalanche paths with wind-loaded start zones is not recommended.

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2

    Snowfall will taper off this morning and the recent snow will become less sensitive throughout the day. The Mammoth area received the lion’s share of precipitation, which is where the problem will be largest and most dangerous. Soft, cohesive slabs of recent snow and sluffs fanning out from a point will be likely 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.

    (3/19/2023)

    Unstable storm snow

  • Deep Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2.5–4

    Deep Persistent slab avalanches failing within older layers of snow from February have become a low likelihood/high consequence scenario. Human triggering of these layers is unlikely, however, there is the potential for large wind slab avalanches to step down. If triggered, expect deep slabs to propagate widely, connect multiple start zones and terrain features, and run long distances to valley floors. Features of concern include shallow trigger points, steep complex terrain, convexities, and slopes with overhead hazards like cornices or big start zones. You can decrease your exposure to the problem by limiting time spent in the tracks and runouts of large avalanche paths. Uncertainty is high and avalanches could be unsurvivable.

    (3/15/2023)

    Nevahbe Ridge deep slab avalanche

     

     

Avalanche Discussion

The storm that will clear out of our area today has had the biggest impact on the area surrounding Mammoth. Yesterday, forecasters found touchy wind slabs in the Lakes Basin and we have reports of avalanches in the Sherwins. As of this morning, this area has picked up over 2 inches of snow water equivalent, and over 16 inches of new snow. Southwest winds have been moderate to extreme. North and south of Mammoth, snow totals are between 3 and 8 inches with less than an inch of new water. A forecaster in Lee Vining found reactive loose dry avalanches below treeline yesterday.

The weather changes today as the storm clears. Southwest winds are forecasted to continue at snow-blowing speeds for the majority of the day. And they’ll have right-side-up new snow to transport. As skies clear and temperatures rise below treeline, loose dry snow could become loose wet. 

The last reported deep slab avalanche was a natural D4, witnessed south of the forecast area near Owen's Point on 3/15/23. While snowpack tests in the Mammoth area and north since the 14th have indicated that weak snow buried in mid-February is becoming more unreactive, a party touring just south of the Bishop zone reported collapses just 72 hours ago. That indicates that where the snowpack is thinner, like the southern half of the forecast area, avalanches stepping down to deep layers are more likely. 

Keep in mind that the recent run of high-intensity storms has had serious impacts on communities, infrastructure, and road crews. Considerate travel choices and strategic parking will be appreciated if you decide to venture out today. With good coverage at lower elevations this winter, recent avalanches have been running further, impacting roadways and buildings in the communities of Virginia lakes, Mono City, June Lake, and Aspendell. It is important to practice good run-out awareness. Triggering an avalanche above infrastructure could have devastating consequences.  Have a backup plan, remember that it often takes multiple passes to clear roadways and trailhead parking. Road crews are working overtime to allow access to communities that have recently been stranded by heavy snow, avalanche activity, and flood damage. Blocking snow drifts, travel routes, and snow piles makes it impossible for road crews to continue their work.

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