Bulletin d’avalanche

Salmon River Mountains

Payette Avalanche Center
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Danger d’avalanche

Sat
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 8 months ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Heavy snowfall, fluctuating temperatures, elevated rain/snow levels, and strong winds have created dangerous avalanche conditions. Above 6,500 feet, you're likely to encounter wind slabs 1-1.5 feet thick. Wind slabs will be thickest and most reactive on north and east-facing terrain. If you're observing signs of instability, such as shooting cracks, it's time to back off steep terrain and/or find another aspect.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    8-12 inches of dense, heavy snowfall along with strong SW winds have created wind slabs 1-1.5 feet thick. You're most likely to encounter wind slabs above 6,500 feet, especially on north and east-facing terrain features. Look for evidence of wind-loading like fresh cornices, pillows, dunes, or drifts. Be on the lookout for obvious signs of instability, such as shooting cracks. If you're finding a dense, hollow slab of new snow, it's time to back off steep terrain and find another aspect that is not harboring wind slabs.

    Local terrain features can influence the prevailing wind direction. Micro-terrain features across all aspects of the compass such as gullies and ridgelines can become cross-loaded. Be alert to the aspects you're traveling on and how winds have loaded those slopes.

Avalanche Discussion

Winter has finally arrived in the West Central Mountains. Along with the aforementioned Wind Slab problem, I would have my guard up for several reasons today:

  • Uncertainty exists about the snowpack structure above 7,500 feet. Due to recent weather and challenging travel conditions, we have limited information above 7,500 feet.
    • What we know : a deeper snowpack exists with 3-4 feet of snow; we have been tracking at least two persistent weak layers over the past few weeks; last week's rain/snow levels pushed up to 8,500 feet.
    • What we don't know :  how have the persistent weak layers responded to the weather events of last week; how thick is the ice/crust complex from last week's rain event; if the snowpack is still harboring dry, weak snow from October & November.
  • Yesterday's storm came in "upside down". Meaning colder, lighter snow fell beneath heavy, wetter snowfall later in the day. This creates instabilities within the new storm snow.
  • New snow has been falling on slick crusts from last week's rain and warm temperatures. Yesterday, we observed new snow showing signs of poor bonding to this crust. You can read my observation HERE. 
  • Rain has been falling below 6,000 feet since early this morning. Rain falling on 8-10 inches of new snowfall will create wet loose slides at lower elevations. There is very little existing snow cover in this elevation, but it's something to have on your radar for today.

Despite the excitement around a foot of recent snowfall, coverage in the mountains is still very thin for this time of year. Off trail travel on snowmachines is nearly impossible right now. Logs, rocks, and the like will be lingering just beneath recent snowfall.

Help us paint a picture of our evolving snowpack across a large area. Even general information, such as snowpack depth on a given aspect, can help inform our forecast and the broader community. Drop us an ob below:

Submit an online observation HERE

  • Tag us #payetteavy
  • Download the Avy App HERE

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