Bulletin d’avalanche

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Danger d’avalanche

Wed
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 5 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

You are most likely to encounter avalanches in areas where the wind has added weight to weak layers in the snowpack. These weak layers exist in the upper snowpack and near the ground. You can significantly reduce your risk of triggering an avalanche by choosing terrain that is sheltered from the wind.

Conditions continue to be more dangerous near the Smoky Mountain crest/Dollarhide Summit where the recent storm hit the hardest. 

Problèmes avalancheux

  • Wind Slabs

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

    Last week's storm dropped 12-30" of new snow in this zone, accompanied by strong winds. The greatest amounts fell from Dollarhide Summit SW towards the Soldiers. Despite lower snow totals around the Wood River Valley, small, natural, and skier-triggered avalanches were reported this past week, and a fresh natural wind slab was reported yesterday (photo above/right). Wind slabs will be most common at upper elevations, but this week's wind also drifted some open middle and lower elevation terrain (example).

    These slabs have had a bit of time to bond to the surfaces that they were deposited on but there are still places where you can trigger them. In this zone, these wind slabs are most concerning where they overlap with the persistent slab problems described below. Stiff slabs on top of weak layers (those in the middle of the snowpack as well as at the base) are never a good combination. 

    ADDITIONAL DISCUSSION A crust+facet combination exists underneath last week's storm snow on slopes that directly face the sun (southern half of the compass). This layer produced a number of large, natural avalanches in neighboring zones during the recent storm:

    •  SW Bowl of Galena Peak (photo)
    • In the Boulders near Mushroom Ridge
    • Behind Horton Peak in the Pole Creek drainage (photo).

    Time will tell how long this layer will be problematic, but I'll be particularly leery of slopes where this layer exists for the next bit.

    (1/8/2022) Small natural wind slab avalanche in Croy Canyon. 6800’, E. Photo: V. Rossin

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–3

    Weak October snow is buried 2-5+' deep on most shady middle and upper elevation slopes. Some sunnier, upper elevation aspects have this layer too. The recent storm event just added a huge load to this weak layer, especially on wind-loaded slopes. It is the most deeply buried near Dollarhide Summit SW to the Soldiers. The recent storm largely missed the mountains above the Wood River Valley, but avalanches observed earlier this season indicate that this weak snow is problematic where it exists. 

    Where are you more likely to trigger an avalanche on this layer? Most savvy backcountry skiers and riders are still avoiding very steep (>35 degrees), rocky, wind-affected slopes at upper elevations and in alpine terrain.

    (1/3/2022) This large persistent slab avalanche was observed above the East Fork of the Big Wood River prior to the recent storm. It failed on facets (October snow) buried near the base of the snowpack.

Avalanche Discussion

WEAK LAYER and SLAB DISTRIBUTIONAfter a wild month of nearly continual snowfall and wind we find ourselves in a period of clear skies, cold temperatures, and light winds. The calm after the storm. This is a great time to take stock of the state of the snowpack and think about the variability that we are seeing across our area. The first two rounds of storms (mid-December and near Christmas) brought a big helping of snowfall to most of our region. A bit more snow fell in our northern and western mountains (Banner Summit area, Sawtooths, Western Smokys, Soldiers) but the mountains above the Wood River Valley and those on the eastern side of the Big Wood and Salmon Rivers (Pioneers, Boulders, White Clouds) picked up their fair share. These storms buried a layer of weak snow that had stuck around after our first big snowfall of the year in late October. This October snow was preserved on shaded slopes at middle elevations and most slopes at upper elevations. The December snowfall pattern left a thicker slab of snow on top of this weak snow in the more favored areas (north and west) and a thinner slab to the south and east. Simple enough.

The most recent storm (January 3-7) heavily favored the northern mountains and left the good people of the Wood River Valley wondering, "storm, what storm"? In areas favored by this storm, we saw widespread avalanches related to the new snow (wind slabs, storm slabs, loose snow avalanches) as well as a pattern of activity that pointed to the involvement of a weak layer buried at the base of this storm snow. This layer appears to be at its worst on slopes that face the south half of the compass, where it exists as a subtle crust with facets above and below. In the areas favored by this storm, this layer is buried 2-3.5' down under a meaty slab of snow. In the areas that were missed by this storm, this weak snow is much closer to the surface. This is starting to feel a little more complex.

If we mentally zoom back out, we can see that we have patterns of weak snow and slabs that vary widely by aspect and elevation, and between forecast zones. If you want to completely avoid areas where either of these weak layers exists you will have to do quite a bit of thinking and planning. As the likelihood of triggering avalanches on these weak layers slowly decreases and the Avalanche Danger slowly comes down, we find ourselves in a tricky place. Avoiding avalanche terrain is pretty simple, but deciding when and where to engage with avalanche terrain is very complex. When you are out in the mountains today, think about these patterns and whether or not these weak layers exist in the terrain you are playing in. The danger may be MODERATE in all of our zones, but the snowpack is different everywhere you go. Whether or not you choose to enter avalanche terrain is up to you, just be sure you know what sort of dragons you are choosing to engage with.

Régions couvertes