Lawinenlagebericht

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 6 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Triggering a larger avalanche remains possible in the eastern portion of this zone—the Little Wood drainage, Pioneer Mtns, and near Bald Mtn—where 16-20 inches of recent snow fell on a weak snowpack. Wet snow avalanches will become possible as the day warms up. These will be most likely on slopes getting hit by the sun, and on all lower elevation slopes.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    The southern Pioneer Mtns (including the Little Wood drainage, Mormon Hill, and Swede Peak areas) as well as Bald Mtn near Ketchum, received 16-20” of dense snow early last week. This new snow fell on persistent weak layers that formed during the February dry spell and resulted in several large, natural persistent slab avalanches. Some of the slides were hundreds of feet wide (photo to right), failing at the interface between the new snow and the old rotten snow on shadier slopes. Today, you are most likely to trigger a slab avalanche where the wind has affected the snow, but slides large enough to bury people are possible in sheltered terrain too. 

    You may be able to trigger slides remotely: from flatter terrain above, below, or to the side of a steep slope. Choosing lower angled terrain is the only way to safely "manage" this problem. 

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1

    Observations yesterday indicated that things were pretty quiet on the wet slide front. I would expect a similar pattern today, but continue to monitor snow conditions as the day heats up and slopes get cooked by the sun. Loosely speaking, there are two types of wet snow problems to watch for:

    • At lower into middle elevations, the snowpack is in a typical melt-freeze cycle—starting out strong when frozen in the morning, and weakening as it becomes wet with daytime warming. Where the snowpack is shallow and weaker, this type of wet slide could gouge down to the ground once it gets moving (see photo at right).
    • At middle and upper elevations, loose snow avalanches could involve the recent snow that fell since the weekend. This will be more likely on E and W-facing slopes that are transitioning from dry to wet snow, but could extend into S aspects too.

Avalanche Discussion

With the important exception of the SE corner of our forecast area, the snowpack throughout the regions is relatively stable and triggering a large avalanche is unlikely.

In the Little Wood drainage, the Pioneer Mtns, and near Bald Mtn, 16-20 inches of new snow fell earlier this past week. February was exceptionally dry in this particular area, which led to widespread faceted snow on mid and upper elevation shady slopes. When Ben went into this area a week ago, he observed several large natural avalanches (photo). While it's been a number of days since the snowfall ended, these type of persistent slab problems don't go away quickly. Triggering a dangerous avalanche—large enough to bury or kill you—remains possible in this portion of the forecast area. You're most likely to find this problem on mid to upper elevation slopes that face NE-N-NW.

The rest of the forecast area to the north and west received about 8-14 inches from this same storm, which wasn't quite enough load to lead to widespread instability. Here, we're trending towards a stable snowpack with the typical wet snow problems as the day heats up and the possibility of finding an isolated wind slab. Maintaining situational awareness as you move through the mountains will help you recognize and avoid these problems. How does the snow change as you go up in elevation and move onto different aspects? How are things changing as the day warms up? LOW danger is a double-edge sword—decreased likelihood of triggering a slide, but often we gravitate towards more consequential terrain where even a small slide could be dangerous.

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