Bollettino valanghe

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Sawtooth Avalanche Center
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Pericolo valanghe

Fri
Alta quota
4 · Forte
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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In sintesi

Very dangerous avalanche conditions will develop this afternoon as a powerful storm brings heavy snowfall and strong wind. Naturally occurring 1-3 foot thick avalanches may break widely on buried weak layers. Slides can be triggered from long distances away from the slope that releases. It would take some bad luck, but triggering 4+ foot thick avalanches on deeply buried weak layers is not out of the question. 

AVALANCHE WARNINGS may be issued this evening as the intense storm continues overnight. 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–3

    You're likely to trigger large avalanches on many slopes. These slides will break widely on a weak snow interface, including slick facets, crusts + facets, and surface hoar, buried and preserved by Monday's storm. Today's heavy snowfall and strong wind will double the thickness of these slabs by sundown, creating dangerous avalanche conditions on all aspects and elevations, including areas sheltered from the wind. 

    Anticipate touchy conditions that will only worsen late in the day and as you climb into windier terrain. Persistent Slab avalanches can release in surprising ways. You can trigger them from flat or low-angle terrain long distances away from steep slopes, and they can break far above you. Snowpack cracking and collapsing are obvious clues that the slab + weak layer combination you've encountered is unstable. 

    ADDITIONAL DISCUSSION: The shallower Persistent Slabs described above have the potential to step down to release a very large, destructive 4+ foot thick avalanche. These slides would fail on persistent weak layers in the middle or base of the snowpack. The chance we see these beasts will only increase as the storm intensifies this evening and tomorrow.  

    (2/26/2024) This slab avalanche released during an intense period of precipitation on Monday. Today's storm will add to these slabs, creating dangerous conditions on many steep slopes.  Photo: VandenBos

  • Wind Slabs

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

    Today's 5-12" of snow and strong S and SW wind will build fresh, sensitive wind slabs in exposed terrain. Given the intensity of the wind, anticipate these slabs on any open slope, including the mouths of main drainages and roadways that typically funnel wind.

    While dangerous on their own, these fresh slabs are likely to release on the persistent weak layers described above. Cornices will grow rapidly, calving off to release slabs on the slopes below. Drifts, dunes, rippled snow surfaces, and chalky snow pillows are clues that the wind has been at work. If you're experiencing whiteout conditions, you're traveling through the most dangerous overlap of today's avalanche problems. 

    (2/27/2024) This slab avalanche was triggered Tuesday from 50 ft away on a low-angle ridgeline. It broke widely in wind-drifted snow on a thin layer of facets above a crust. Cracks extended another 100' cross-slope beyond the crown. Smiley Ck, ENE @ 9,100'. Photo: Sawtooth Avalanche Center

Avalanche Discussion

A powerful storm is directing a fire hose of atmospheric river moisture at our region. Expect wind speed and snowfall intensity to increase throughout the day, causing whiteout conditions. The chance of natural and human-triggered avalanches will increase rapidly this afternoon and overnight, creating very dangerous avalanche conditions in many areas. AVALANCHE WARNINGS may be issued this afternoon. 

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