Bulletin d’avalanche

Banner Summit

Sawtooth Avalanche Center
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Danger d’avalanche

Sat
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Look for large, sensitive cornices, drifts, and slabs in areas exposed to the wind. These will be thicker and more widespread as you climb above about 9,000 feet. Cracking is a sure sign that you've found a touchy slab. The snowpack below 9,000 feet is complicated and highly variable.  Expect a wide range of conditions influenced by recent strong wind, heavy rain, and wet snow. Avalanche conditions are fundamentally different than they were prior to this storm. Increase your safety margins to handle this uncertainty. 

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1.5–2

    Two-day storm totals at upper elevations near Banner Summit should reach 12-18" by this afternoon. Snowfall has been accompanied by moderate to strong S and SE wind. Expect to find 1-3' thick wind slabs near exposed ridgelines and mid-slope gullies. These slabs will be thicker and more widespread as you climb above about 9,000'. Anticipate sensitive, thick, heavy pillows and cornices to guard the entrances of many steep slopes. Give these features a wide berth. While dangerous in their own right, failing cornices may trigger a large wind slab on the slope below. 

    Overlapping slabs and heavy, dense storm snow may make wind-affected terrain harder to identify. Pay attention to the depth and character of the new snow you're traveling through. Cornices, dunes, rippled snow, and areas with stiffer snow surfaces are clues that the wind has been at work. Cracks shooting in front of your skis or boards mean you've found a sensitive slab. Even small slabs can knock you off your feet or your machine. Consider the consequences of being caught before committing to riding steep terrain. 

Avalanche Discussion

Today's snowpack is not the relatively straightforward and predictable environment we've enjoyed over the past week. On the contrary, the complexity and uncertainty of what we'll find out there has increased dramatically. Soaking rain, intense thunderstorms, heavy wet snow, and strong to extreme wind have reset the table in unpredictable ways. Here are some things to keep in mind as you head back into the hills:

Above ~9,000'New snow and wind are the main factors driving the avalanche hazard here. While some rain did fall, most precipitation fell as snow. Wind slabs and sensitive cornices should be top of mind. Dense snowfall can rapidly build large cornices and thick slabs. These hazards can grow abruptly as you climb in elevation. 

Middle GroundThis is by far the trickiest terrain today. Wednesday night and Thursday's rain was the most significant rain-on-snow event of the season. Rain lines began above 9,600' before lowering to around 7,500' yesterday. Skiing and riding through these elevations is an uncertain adventure with many unknowns. You may encounter a wintery snowpack at the top of a run that quickly deteriorates into trapdoor wet glop. Middle elevation NW-N-NE facing slopes may be particularly dangerous today. These slopes were dry before the storm. Now, they've absorbed up to an inch of rain and are capped with wind slabs. Stability in this elevation band can change quickly with both aspect and elevation. Don't assume you have it figured out. Carefully evaluate (and re-evaluate) conditions before committing to riding steep terrain. 

Below ~7,500'What's left of the snowpack below 7,500' is a wet mess. Any thin crusts you find this morning may just barely keep you afloat above unpleasant glop. It will take a few days for the snowpack to drain and refreeze. Until then, mild afternoon temperatures or any short bouts of sunshine will find you sinking into mush. If this happens, wet avalanches remain a possibility on very steep slopes. 

Enjoy the new snow, but do so with curiosity and a conservative mindset. Let's all take a collective step back as the snowpack adjusts to the wild spring weather.

Régions couvertes