Lawinenlagebericht

Banner Summit

Sawtooth Avalanche Center
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Lawinengefahr

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

Kernpunkte

Sizable avalanches are unlikely, and most slopes are safe. Watch for isolated wind drifts and cornices at upper elevations. Very steep slopes that directly face the sun could produce small, natural loose snow avalanches (sluffs). 

Lawinenprobleme

  • Wind Slabs

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

    Last weekend's wind and snowfall formed small drifts and slabs at upper elevations. Tuesday in the Sawtooth Mountains near the head of Beaver Creek, a skier triggered a small slab avalanche just below a corniced ridgeline (see photo). The slab failed on a subtle sun crust on an E-facing slope at about 10,000'. These small slabs may remain sensitive today, particularly where they overlie facets associated with a crust. 

    Watch for smooth pillows of stiffer snow, dunes, or wave-like patterns on the surface. If the new snow depth rapidly increases and feels stiffer than loose powder, you've found a wind slab. Snowpack cracking is an obvious sign that you've found a sensitive drift. These slabs are unlikely to produce an avalanche large enough to bury a person, but triggering one in the wrong place could bring serious consequences.

    Cornices grew in the past couple weeks, forming curls and overhangs in some exposed terrain. Give any large features a wide berth.

    ADDITIONAL DISCUSSIONSun-induced loose snow avalanches are possible today. Avalanche activity will follow the arc of the sun beginning on E-SE aspects in the morning, shifting to S-facing slopes during the day, and moving over to SW-W aspects in the afternoon. Pay attention to what's above you. These slides are most likely in very steep, rocky terrain sheltered from the wind. Herds of snowballs rolling down a slope or wet and sticky snow beneath your feet are clues that the snow surface is weakening. 

Avalanche Discussion

As usual, the Sawtooths and Banner Summit boast the deepest snowpack in our forecast area. The big January storm (30-50” of snow in 5 days) overloaded the depth hoar and facets near the ground, producing a widespread, deep slab avalanche cycle. Since that storm, this area has received well below average snowfall. The weak layers responsible for the January avalanche cycle look a lot better than they did in January; for now, they are hibernating, or dormant. Also, the weak layers are buried far enough below the surface (typically well over 3 feet) to significantly reduce the chances of people triggering large avalanches.  

We now have what I like to call a "what-you-see-is-what-you-get" snowpack (WYSIWYG for short, or phonetically, "whizzy-wig"). Meaning, we're not likely to get surprised by deeper weak layers. Instead, the danger rises during a storm, subsides in the following days and we start over again, dealing mainly with new snow instabilities near the surface. The storm over the weekend built soft slabs in the alpine, one of which was triggered on Tuesday. Sun and warm temperatures are working to help those slabs heal but are also initiating sun-induced loose snow avalanches. The good news is, these small sluffs are easy to anticipate and avoid. 

There are lots of generally safe places to enjoy the day but a winter mountain environment is never devoid of avalanche danger. Continue to practice safe travel techniques: give cornices a wide berth, ski or ride one at a time, and keep an eye on each other. If you find a small sensitive slab, don't write it off as an "outlier". If something doesn't feel right, back off and come back another day. The consequences of even a small slide are amplified in extreme terrain. 

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