Boletín de aludes

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Peligro de aludes

Tue
Alta montaña
4 · Fuerte
Límite del bosque
3 · Notable
Bajo el límite
3 · Notable
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Desactualizado: este boletín caducó 2 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

You can trigger avalanches large enough to bury you on many slopes today. A storm brings up to 11 inches of new snow by 5pm and sustained strong winds. Avalanche danger will rise to become very dangerous throughout the day.  Avoid traveling on or underneath slopes steep enough to avalanche. Slides can be triggered from long distances away from steeper slopes and can run into gentler terrain below. Dense freshly forming wind drifts will be sensitive to your weight, especially as you climb higher in elevation. 

Conditions will be at their worst where more snow is falling in this zone's northern and western portions, including the White Clouds.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2

    Sustained strong winds began 2 days ago and increased overnight. The ongoing storm will bring up to 11 inches of snow and sustained strong winds to the western end of this zone. Expect to find a range of problems involving this new precipitation. At upper and middle elevations, you'll find reactive wind slabs and you may be able to trigger loose snow avalanches that run fast and far on weak, slick surfaces. In sheltered middle elevation terrain, expect to easily trigger slides the new snow that may have a loose characteristic to them, gaining mass and speed as they run downhill. Importantly, natural and triggered slides involving the new snow can trigger the much larger, more destructive persistent slabs described below. 

    These slides will be largest and most reactive in the western portion of this zone where more snow is falling. These certainly can be large enough to bury you, and at their smallest, largest enough to take you for a ride down through consequential terrain. Rippled snow surfaces, dunes, pillows are all signs that the wind has been at work. The ongoing light-density snowfall and wind may make it harder to identify where wind slabs exist.

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1.5–3

    Triggering large to very large avalanches here is a disconcerting possibility. With the additional 11 inches of snow that will fall and strong winds throughout the day today, more stress is being added to these weak layers. These slides come in two flavors:

    • Weak snow from December forms the base of the snowpack and has produced dozens of avalanches large enough to turn your car into scrap metal. A very dense slab rests uncomfortably on top of this weak snow. This slab makes triggering one of these avalanches much more difficult, but the resulting slide would be destructive and likely unsurvivable. The first sign of instability on this weak layer will be the very large avalanche you trigger. The most likely terrain for making one of these beasts is steep, rocky, wind-affected terrain where the snowpack has thinner spots that give you access to the weak layer. 
    • Several weak layers exist in the upper 12-18 inches of the snowpack. These layers are highly variable. On some slopes they are well bonded, while on others they are producing large avalanches. You may find good stability on one slope and then trigger an avalanche when you change to a nearby slope. Cracks shooting out from your skis or machine are a clear sign you've found an unstable slab. The human-triggered slides that have failed on this layer have involved crust+facet combinations and have been triggered from a distance (remotely). 

    Persistent Slab avalanches behave in ways that catch experienced users off guard. You can trigger them from flat or low-angle terrain long distances away from steep slopes, and they can break far above you. Dozens of skiers or riders can ski/cross/highmark large slopes before a very avalanche releases. 

Avalanche Discussion

A winter storm will bring up to 11 inches of new snow to the Galena Summit & Eastern Mtns Zone by 5pm tonight, but there's a lot more nuance to how this storm will impact the snowpack. Avalanche forecasting at a regional scale is an imperfect science — we are forced to tell you what will happen across wide geographic areas that may be impacted by significantly different weather. Our current storm is riding in on a NW flow, meaning it will drop significantly more snow in the western and northern portions of this zone than in its eastern reaches. Western locations like Galena Summit and Baker Lake will receive just under a foot of snow, while the Pioneer Mountains will receive just around six inches of snow. 

In the eastern portion of this zone, the sustained strong, westerly winds will be the main architect of new instabilities in the snowpack. Even with less than a foot of snow falling, sustained strong winds are enough of a force to load slabs large enough into starting zones to create slides that may be large enough to bury you. At upper and middle elevations, you'll find reactive wind slabs and you may be able to trigger loose snow avalanches that run fast and far on weak, slick surfaces. In sheltered middle elevation terrain, expect to easily trigger slides the new snow that may have a loose characteristic to them, gaining mass and speed as they run downhill. Importantly, natural and triggered slides involving the new snow can trigger the much larger, more destructive persistent slabs.

Now, take these conditions, but imagine them with almost double the amount of snowfall in the western portion of this zone. Expect each of these same issues to be worse here. This means larger wind slabs, more snow running in loose snow avalanches, and most importantly more load onto the existing persistent slab problem. Large natural persistent slab activity will become a concerning possibility here throughout the day, with the potential for slides to break deep into the snowpack and run to valley bottoms. While the avalanche danger is HIGH across this zone, just know that depending on where you head out today, you may find two, or a few, different shades of red. 

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