Bollettino valanghe

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

As sun and rising temperatures heat the snow, natural and human-triggered wet loose slides will become likely on slopes directly facing the sun. Also, you could find wind drifts sensitive to triggering in upper elevation terrain. Look out for smooth, pillowed patches of snow close to ridgelines. 

Problemi valanghivi

  • Loose Wet

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

    As the sun and warmer temperatures heat up the snow, it will eventually lose cohesion and natural wet loose avalanches will become likely. This problem will be most common where more than approximately 6” of new snow fell in the last few days. 

    Fortunately, this problem is fairly easy to manage by keeping close track of the snow surface. 

    • Is the sun directly hitting the slope you’re on or below? 
    • Is the snow getting soft and mushy?
    • Can the snow no longer support your weight if you step off your skis or sled?

    If you find yourself in this situation, it is time to move to cooler, shaded slopes, or the apres-ski.

    Recognize that you don’t need to trigger wet loose avalanches; they have a nasty habit of happening on their own (natural avalanches). Don’t spend more time than you need to below steep, rocky terrain that faces the sun and is sheltered from the wind.

  • Wind Slabs

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

    The light winds and snowfall over the past few days built some soft slabs in alpine and exposed upper elevation terrain. Yesterday, in the adjacent Galena Summit zone, I got cracking in fresh drifts at upper elevations in the Boulder Mountains. Scott got unstable snowpack test results in the Smoky Mtns (photo). The wind slabs appear to be thicker and more reactive on NE and NW aspects where they may have formed above a sandwich of crusts and weak, sugary snow.

    Look for evidence of wind drifting such as smooth pillows of snow, dune-like drifts, ripples on the snow surface, and fresh cornices along ridgelines. Cracks shooting out from your skis or board are a sure sign that you've found a sensitive wind drift. If the snow suddenly gets stiffer as you're moving on a steep slope, it's time to pay close attention and evaluate your terrain choices.

Avalanche Discussion

The avalanche danger scale is a five-step scale that avalanche forecasters use to communicate information about the avalanche hazards you might encounter in the backcountry. Of course, the world doesn't fit neatly into five boxes. There are innumerable shades of gray and subtleties that our simple scale glosses over.  Today, the avalanche danger at upper elevations is mostly MODERATE; however, the type of slide that you might trigger varies significantly over space. Some details:

  • Pioneer Mountains, Little Wood drainage, and Smoky Mtns near Baldy: The southeastern corner of our forecast area got clipped by a significant stream of water since this weekend. While many of our other zones and areas picked up 6-14" of snow, this area is approaching 20" of snow and 2" of SWE (snow water equivalent). This relatively large, rapid load stressed a very weak snowpack for the first time this season; numerous large, natural persistent slab avalanches occurred. These types of slides can be triggered remotely, including from flat ground below avalanche paths—spooky! Dealing with this problem involves building wide safety margins into your travel plans.
  • Sawtooth, Smoky, White Cloud, Soldier, and Boulder Mountains: 6-14 inches of snow fell in the past few days. Light to moderate winds built small slabs in some upper elevation terrain. 
  • All areas with more than 6” of fresh snow on the ground: With the weather forecast calling for a warm and sunny day, we expect to see widespread natural wet loose avalanches involving the surface snow. I don't expect these slides to be large, but they could push you around or carry you into places you don't want to be. 

What tools or travel techniques will you use to manage these problems? The "simple" wind slab and wet loose problems present hazards that are predictable and easily avoidable. If you choose to enter avalanche terrain with this type of problem, you know what to look for and avoid. However, a persistent slab problem is an entirely different beast; you need to "close" large chunks of terrain to effectively manage this problem.

For all of the avalanche types or problems on today's menu, natural and/or human-triggered avalanches are possible—the kicker is the way you deal with the various problems is very different.

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