Lawinenlagebericht

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
Auf der Karte ansehen

Lawinengefahr

Wed
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
Open full map
Veraltet — dieser Lagebericht ist 7 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Triggering large, 1-3 foot thick slab avalanches continues to be a possibility. Buried weak layers underneath these slabs produced recent natural avalanches. To reduce your risk, choose gentler slopes and avoid terrain where the wind has built slabs and added stress to the weak snow below.

Lawinenprobleme

  • Persistent Slabs

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

    We are nearly a week out from a significant loading event, but recent natural avalanche activity continues to highlight instabilities in the snowpack. Unfortunately, buried weak layers from earlier in the season are proving slow to heal. Here are a few notable recent avalanches involving this weak snow:

    • On Sunday, in the Baker Creek drainage, I observed a slab avalanche that appeared to have failed naturally that day under the influence of warm temperatures and direct exposure to the sun (photo at right). 
    • That same day, Sun Valley Heli Ski staff reporting seeing a large avalanche that likely failed sometime on Saturday (photo)
    • Yesterday, near the headwaters of the Salmon River, I spotted a similar slab avalanche that likely failed on Sunday (photo).

    These avalanches are clear indicators that triggering slides on the  weak layers buried 1-3’ deep continues to be a worrisome possibility. The pattern of this recent activity indicates that slopes that directly face the sun may be touchier than those that don’t. Reduce your exposure to the hazard posed by this problem by choosing gentler slopes and avoiding terrain with aging wind slabs from last week's storms. These slabs add extra stress to the weak snow underneath.

    ADDITIONAL DISCUSSIONPrecipitation starts again this afternoon. Wind speed will increase a bit late in the day and overnight as the storm exits our area, shifting from SW to NW. Fresh wind slabs will be small, but may be touchy. More importantly, these slabs will add stress to the weak snow underneath. Also, one of these much smaller, fresh slabs may be able to trigger a larger, deeper slab as it travels downslope.

Avalanche Discussion

With each passing day without additional loading we are trending towards the dreaded “scary moderate” stability rating. Avalanche hazard is the likelihood of an avalanche impacting something of value — for our purposes, that thing is you. As the likelihood of an avalanche occurring decreases, the avalanche danger also decreases. But it gets tricky: as the likelihood of triggering a slide decreases, the consequences of such a slide remain constant. 

This scenario is commonly referred to as “low probability, high consequence,” or LPHC for short. LPHC events are very tricky to deal with, in the backcountry and in life in general. Each individual has to decide what threshold of risk is acceptable for them. Most people have decided that flying in an airplane is an acceptable risk. The odds of an airplane crashing is commonly cited as 1 in about 5 million. How much higher would these odds need to be before you decided you wouldn’t fly anymore? 1 in 1 million? 1 in 100,000? 

When dealing with persistent weak layers, even subtle changes in the snowpack can impact stability and keep the snowpack on edge. Put simply, our snowpack doesn’t need a quick trip to the spa, it needs an extended cruise in the Caribbean. Over the past few days the snowpack has been agitated by prolonged exposure to air temperatures near freezing. A quick shot of snow tonight will continue to irritate our weak layers. As you travel through the backcountry today, recognize that you are dealing with a LPHC problem who’s odds are impossible to know with certainty and are continually changing. The best way to reduce your risk is to build in wide safety margins into your travel decisions. Be aware of the terrain that you are traveling through and underneath and be alert of the consequences of being caught in a slide in that terrain.

Details from Wednesday's Avalanche Accident in Baker Creek:On Wednesday, January 15th, 2020, a snowmobiler was caught and killed in an avalanche in the Baker Creek drainage, approximately a half-mile northeast of Baker Lake. We visited the site Thursday to collect data on the avalanche. This video contains preliminary information collected during the site investigation; a full accident report will be published soon.

Abgedeckte Regionen