Bollettino valanghe

Salmon River Mountains

Payette Avalanche Center
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Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 8 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Heavy, wet snowfall and strong winds have created dense wind slabs 1-2 feet thick above 7,500 feet. 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.

Problemi valanghivi

  • Wind Slabs

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

    Recent dense, heavy snowfall coupled with strong W/SW winds have created wind slabs 1-2 feet thick. You're most likely to encounter wind slabs above 7,500 feet, especially on north and east-facing terrain features. Wind slabs in the upper elevation are likely overlying crusts and buried weak layers. These dense wind slabs could behave differently than a typical wind slab and should be treated cautiously.  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 recently wind-drifted snow.

    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

Another storm with a lot of precipitation and above average temperatures. Snow totals were not nearly as impressive as snow water equivalent (SWE) totals. The mountains picked up 2-3 inches of SWE, with 8-16 inches of snowfall. It looks like the Salmon River Mountain zone was favored, as rain/snow levels rose to ~7,000 feet yesterday along West Mountain. Along with ourWind Slab problem, I would have my guard up for a few other 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.
  • Our recent storm came in "upside down". Meaning colder, lighter snow fell beneath heavy, wetter snowfall. This will likely feel and behave more like a storm slab in terrain that's sheltered from the wind (~below 7,500 feet).
  • New snow fell on slick crusts from last week's rain and warm temperatures. Thursday, we observed new snow showing signs of poor bonding to this crust. You can read my observation HERE. 

Despite the excitement about the 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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