Bollettino valanghe

Salt River and Wyoming Ranges

Bridger-Teton Avalanche Center
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Pericolo valanghe

Wed
Alta quota
4 · Forte
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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In sintesi

Very dangerous avalanche conditions exist. The combination of intense snowfall and wind will create wind slabs that will be large and easy to trigger.  Avalanche conditions will be most dangerous on slopes with windblown snow, but it's also possible to trigger a slide breaking 1-2 feet deep on steep, sheltered slopes.  It will be a good day to stick to lower slope angles, terrain not exposed to steeper slopes overhead, and avoid wind-loaded terrain. Human-triggered and natural avalanches are very likely at upper elevations.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1–2.5

    Heavy snowfall and strong winds built slabs overnight. Expect to find wind drifts 2-3 feet thick in terrain exposed to the wind throughout the day. These slabs will be easy to trigger today and will create avalanches large enough to bury a person. Additional snowfall and wind this morning and into the afternoon will help these slabs continue to grow in size and distribution. Natural avalanches are likely in upper-elevation terrain; pay attention to the terrain above you. On slopes that directly face the sun, slabs are resting on stiff, icy crusts. Any slide you trigger in these areas will pick up speed quickly as it travels downslope. 

    Much of yesterday's snow was transported into slabs, and another round of snowfall overnight made for additional ammunition. Rates of snowfall today are forecasted to be high (1-2 inches per hour). As of 6 AM, it is raining at lower elevations in certain areas of the Greys. Conditions are changing rapidly. As you gain elevation, you will be more and more likely to find these slabs and they will grow in thickness and distribution. They will be the largest and most sensitive in upper elevation terrain where winds are strongest and are transporting the most snow.

    Avalanche conditions will be most dangerous on slopes with windblown snow, but it's also possible to trigger a slide on steep, sheltered slopes.

    (2/20/2023)

    Surface snow showing clear signs of instability on Mt. Taylor, 8600' SE

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    2–3

    We have begun a large storm cycle that will add significant weight to buried persistent weak layers. Two factors prevent this from being a simple case where I can tell you exactly what will happen and when. The first is that the new snow load will be dependent on what pans out with the weather forecast today, as well as the rate of snowfall. The second is that we have a complex and variable snowpack with a number of buried weak layers. As new snow piles up through the day, triggering an avalanche will be most likely on weak layers within the top 1-3 feet of the snowpack or on yesterday's snow surface. It will also become possible to trigger deeper, older layers, resulting in a dangerously large avalanche. 

    Go back to the basics: we have a handful of persistent weak layers, and they are getting loaded with new and windblown snow. When you look at it that way, it's clear that the avalanche danger is on the rise, and we need to scale back our terrain choices by choosing lower-angled slopes. 

    Low-elevation slopes have far weaker snow near the base of the snowpack; if forecasted snowfall pans out in valleys as expected today, avalanches may occur on deeper layers at these elevations. 

Avalanche Discussion

Vitamin W

Old father winter is back and does not want any of us to miss out on our daily dose of wind. Monday night marked a significant shift in our recent weather with an extended storm cycle that breaks last week's dry pattern. Storms provide exceptional tests of a season's snowpack. It's not perfectly clear how our aging weak layers will respond to constant loading and wind. But we do know that natural and human-triggered avalanches will become increasingly common, likely breaking in one of three ways:

  1. We'll likely see some mid-storm instabilities or slides breaking on yesterday's snow surface. These slides will be on the smaller side, and these issues will be short-lived.
  2. Triggering a larger avalanche will be most likely on the old/new snow interface buried Monday evening, in the top 1-3 feet of the snowpack. These will be more likely on crusted aspects. These newer layers of weaker snow and crusts from high pressure are largely untested, making it more difficult to predict their behavior with the forecasted snowfall. 
  3. While less likely, the added load will make it possible to trigger deeper, older layers of weak snow. Especially in areas with a deeper snowpack, these layers have been showing signs of improvement. It's not clear if they have any punches left in them, but shallow portions of this zone with weaker snow remain an issue to be regarded. These avalanches would be very dangerous and break deeply. As the new snow adds up over the coming days, the chances of infrequent and isolated but larger avalanches will increase.

While there is some uncertainty about how our snowpack will react to the impending storm cycle, one thing is clear: the avalanche danger is on the rise, and we need to start traveling more cautiously in the backcountry. This means dialing back slope angles, paying attention to the consequences of going for a ride, and avoiding all wind-loaded terrain. In zones that receive the most snow today, that will likely trend toward avalanche terrain avoidance and low-angle "dad pow." 

Regioni coperte