Lawinenlagebericht

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Kernpunkte

Dangerous avalanche conditions exist. Human-triggered avalanches involving dense, 1-4 foot thick slabs of snow are likely. Avalanches may be very large and destructive and can be triggered from long distances away from steeper slopes. Conservative terrain selection is encouraged today.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    2–3

    Friday's storm brought 16-26" of snow (1.5-2.1" of SWE) to this zone. The rapid loading pushed the layers of weak snow now buried in the upper 2-4 feet of the snowpack past their breaking points, resulting in a widespread natural avalanche cycle. On Saturday, Ethan and I observed hundreds of avalanches that failed on persistent weak layers including the slides pictured at right/above. 

    If you dig down, you'll find facet+crust combinations on slopes that face the sun and thicker stacks of weak facets on shaded slopes. Avalanches that fail on these layers will break very wide, wrapping around multiple aspects and connecting multiple avalanche paths. These slides can run the length of an avalanche path, impacting flat terrain long distances away from steeper slopes. 

    Managing persistent slab problems is difficult. If you want to completely eliminate the risk of triggering one of these beasts you'll have to avoid avalanche terrain. You can reduce (but not eliminate) your risk by sticking to gentler slopes. And don't forget to pay attention to what is above you, these avalanches can be triggered from long distances away from steeper slopes. 

    (3/10/2023) These very lage persistent slab avalanches failed in lower and middle elevation terrain on N-NE-E aspects above Croy Canyon west of Hailey. Old ski and skin tracks are visible on the bed surface of several of these avalanches.

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1.5–2.5

    Friday's storm was accompanied by strong to extreme winds blowing out of the SE-S-SW. The combination of new snow and wind built very large, dense, 1-3 foot thick wind slabs on many slopes. Triggering a wind slab avalanche large enough to bury you is likely today.

    You'll find wind affected terrain at all elevations in this zone. Wind slabs commonly form along ridgelines, near mid-slope terrain features like ribs and gullies, and on slopes near the mouths of drainages. Expect to find slabs in unusual locations, thanks to the strength of the wind. 

    Wind slabs and cornices that fail can be very effective triggers for the enormous, destructive persistent slab avalanches described above in Problem 1. 

    (3/10/2023) This very large slab avalanche failed in a heavily wind loaded location on a NW-facing slope at 6,800' above Croy Canyon. Large amounts of snow are being transported in this photo.

Avalanche Discussion

Friday's storm produced a truly impressive cycle of natural avalanches (video here). Avalanche activity was much most pronounced in our Galena Summit and Eastern Mtns and Soldier and Wood River Valley Mtns forecast zones. Head over to our Avalanche Database (map, list) to browse through some of these, we've entered about 200 avalanches large enough to bury you that occurred since Friday. Notable avalanches include slides on Della and Carbonate Mountains west of Hailey that dammed the Big Wood River (photo here) and hit several houses (photo here). We observed a number of very large natural avalanches in the Boulder and Smoky Mountains that broke thousands of feet wide (photo here). Natural avalanche activity was most widespread on Friday, though Scott observed 5 large natural avalanches that released in the Wood River Valley yesterday as well (observation here).

The Avalanche Warnings have expired, but conditions remain dangerous. Avalanche accidents commonly occur during the period of decreasing danger following major loading events. This is exactly where we find ourselves today. The mountains may not be crashing down like they did on Friday, but that doesn't mean it's time to let your guard down. Human-triggered avalanches remain likely, and the slides you trigger will not be small. Spend a few minutes browsing through the Avalanche Database to get a sense for the types of avalanches you might see and/or trigger out there. 

I recommend you head into the mountains with a conservative mindset today. If you are dead set on entering avalanche terrain, choose terrain where the consequences of being caught in an avalanche are lower. Your likelihood of surviving an encounter with an avalanche is greater in terrain free of terrain traps (creek bottoms, trees, rocks). If you just want to be outside in the mountains and come home safely tonight there are lots of great options; the skiing and riding are excellent in low angle terrain right now. 

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