Bollettino valanghe

Salmon River Mountains

Payette Avalanche Center
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Pericolo valanghe

Fri
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

Dangerous avalanche conditions exist—be careful. You're likely to trigger small to large avalanches of new snow on many wind-affected slopes above 7,000 feet. There are persistent weak layers buried about 2 feet deep that may allow you onto some steep slopes without any obvious signs of instability, such as cracking or collapsing, before releasing, and it is too late for you to escape. The best way to reduce your risk is to stick to lower-angled terrain that is not directly connected to or below steep, wind-exposed slopes. The sun today will make small, naturally occurring loose snow avalanches likely on slopes facing the sun.

Problemi valanghivi

  • Wind Slabs

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

    You may encounter fresh wind slabs 1-2+ feet thick in exposed terrain at middle and upper elevations. Slabs will be thicker and more widespread in alpine terrain. Wind slabs that you encounter may be perched above a slippery crust, making avalanches easier to trigger or wider than you'd expect. Relatively small wind slabs moving downhill could trigger the larger avalanches. 

    Look for wind slabs near ridgelines and on the sides of mid-slope terrain features like gullies and ribs. Surface textures like dunes, ripples, or pillows are clues that the wind has been at work. Cracks shooting out from your skis or machine are clear indicators that you've found an unstable slab. 

    WET SNOW AVALANCHES: Wet snow slides are possible on steep slopes that receive direct sunshine today. The sun popping out can also increase the odds of new snow slab avalanches failing on slippery rain/rime crusts formed near the beginning of the storm. The scope of these slides may range anywhere from 5,000 to 7,000 feet. Subsections of each zone (like Big Creek, which received 1.3 inches of water but only ~4 inches of new snow & has remained well above freezing) may also remain prone to wet snow problems. 

  • Persistent Slabs

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

    The possibility of triggering a 2-4' thick avalanche breaking on a layer of buried surface hoar from valentines day remains possible as test scores have showed propagation into the hard range (ECTP24). This layer of buried surface hoar produced 2 widespread natural avalanche cycles over the past week and  has been found everywhere in our advisory area and has been a problem on shaded and protected aspects. On some slopes these slabs also rest on weak combinations of crusts and surface hoar. 

    The most recent human triggered avalanche involving this snow occurred Saturday, when riders triggered a slope that propagated deeply above them. Triggering an avalanche involving deeper layers of facets from January is less likely than the "2-4 foot thick" fresh slabs listed above, but the consequences are far greater.

Avalanche Discussion

The last storm on 2/24 left us with 9-12 inches of new snow on top of a fresh layer of surface hoar. This new snow caused widespread natural avalanche activity on a deeper layer of surface hoar/crusts with weak snow buried on Valentine's Day, see our observation from Wednesday near Josephine Lake. The storm on 2/24 brought moderate-to-strong southwest-to-west winds. Rain fell to about 7,000 feet in most areas. Above 6,800', the wind has been at work crafting slabs. Recent westerly winds [shifting WNW] will continue to build these slabs in exposed terrain. Expect that these can be affected by a rider's weight today. Temps were cooling yesterday afternoon as the sun had softened the surface. Expect stiffer slabs today as the wind and cooler temps have likely firmed upper-elevation slopes and formed crusts on the new snow on aspects tilted to the sun. 

As the day warms, the odds of triggering avalanches of new snow (either loose or slab) may increase with direct sunshine. Much of the new snow below 7,000' sits on a slippery rain crust. slopes start to see direct sun, expect the avalanche danger to rise. 

All in all, when the going gets complicated, the best approach is to simplify: avalanches of some variety are likely today, and they could be large. When conditions like this exist, the travel advice is simple: maintain good spacing and don't group up in avalanche terrain; avoid steep wind-affected slopes at middle and upper elevations; practice cautious route-finding; and evaluate the snowpack.

Regioni coperte