Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

Tue
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Hot sunny weather will likely cause wet snow avalanches and cornice failures today. Some places may not have refrozen last night, and in those that did, the change from semi-frozen snow to wet mush will happen fast. Once the snow becomes unsupportable or wet snow gets more than a few inches deep this morning, it’s time to move away from slopes steep enough to produce avalanches.

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1–2.5

    Temperatures stayed well above freezing again last night. While the snowpack may have lost enough heat to the clear night sky for a thin, weak refreeze in some areas, other areas may not have refrozen, especially on tree-covered slopes. Today's intense sunshine and warm weather will quickly melt through whatever refreeze did occur and create unstable wet snow on all aspects. Yesterday, a small wet loose avalanche carried the skier who triggered it downhill and almost pushed them into rocks before they stopped. Today's wet snow avalanches could also be large enough to cause problems for backcountry travelers. 

    Wet snow avalanches entrain more snow as they slide downhill, so expect larger activity on long steep slopes. Once the snow becomes unsupportable, starts to feel wet, or pinwheels/rollerballs start occurring, wet loose avalanches will follow quickly. You can reduce the risk of encountering wet snow avalanches by recreating on slopes less steep than 35 ° without steeper slopes above. Timing your day to find supportable snow may not work today since whatever refreeze may exist will melt so fast that conditions will change quickly. 

    (4/9/2023)

    Wet loose avalanche on Flagpole Peak.

    Photo: Public

  • Cornices

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–2.5

    Cornice failures will be likely today as the sun and warm weather weaken the cornices along many ridgelines. Large to massive blocks falling off these overhanging waves of snow could cause problems on their own or trigger wet snow avalanches on the slopes below.

    Predicting exactly when a cornice will fail is nearly impossible. Cornice failures almost always surprise the people who trigger them by failing farther away from the edge than expected and failing much larger than expected. Stay well away from cornices by putting exposed rocks or trees between you and the cornice. Consider avoiding travel on slopes below cornices.

    (4/8/2023)

    Cornices just outside of the Alpine Meadows boundry. One of these collapsed when a skier got within 10 feet of it. More info here.

    Photo: Public

Avalanche Discussion

  • Observers reported widespread wet loose avalanches, large pinwheels, and rollerballs starting around 10 am yesterday all across the forecast area. 
  • Recent new snow may have assimilated with the older melt-freeze crust below it on E-SE-S-SW-W aspects in areas that received three inches or less of new snowfall on Friday. Areas that were wind-loaded or received more snow will take longer for the recent new snow to transition to uniform melt-freeze in the upper snowpack.

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