Bollettino valanghe

Banner Summit

Sawtooth Avalanche Center
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Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

You're likely to trigger a 2-3 foot thick avalanche on many slopes. Wind-drifted terrain is the most dangerous, but you could also trigger a slide in sheltered areas. Avalanches may be triggered remotely—from gentler terrain above, below, and to the sides of steep slopes.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2–3

    Triggering a 2-3' thick persistent slab avalanche is likely on many slopes. Chris' video (above/right) exemplifies this problem. Persistent weak layers (sugary facets, surface hoar, or crusts) exist on most aspects and elevations. The weakest facets we've found are on shadier aspects.

    Thick slabs are more common as you climb into terrain that's exposed to the wind. Recently wind-loaded slopes with stiffer snow in the top couple of feet of the snowpack are the most likely to produce large avalanches. You're less likely to trigger a large avalanche on lower-elevation slopes and those more sheltered from the wind.

    Snowpack cracking and collapsing are clear symptoms of an unstable snowpack. Tilt that collapse onto a steep slope, and you're flirting with an avalanche. Collapses can travel large distances releasing avalanches above you or on nearby steep slopes. Wind-loaded areas feel stiffer under your skis or sled and are more supportable. Don't be fooled, the weak snow beneath the slab still exists (video).  

    Unfortunately, avoidance is the only way to effectively manage this problem. Skiing or riding steep terrain is a risky roll of the dice. Recent reports of skier-triggered avalanches, abundant cracking and collapsing, and a widespread poor snowpack structure (dense slab + weak layers) are all the reasons I need to continue to travel conservatively. 

Avalanche Discussion

Even in the absence of last night's storm, we'd still be faced with CONSIDERABLE danger. Recent reports of skier-triggered avalanches, abundant cracking and collapsing, and a widespread poor snowpack structure (dense slab + weak layers) dictate this. Yesterday, observers near Galena Summit reported widespread collapsing, including while traveling on existing skin tracks. Another recent observation from near Galena Lodge reported collapses so sudden and loud that her Christmas Tree gathering mission sounded like it was at a shooting range. Certainly, stability has improved slightly since the end of our last storm 5 days ago, but not enough to move the needle on my conservative travel approach.

Although the danger remains CONSIDERABLE, today may be tricker and more dangerous than yesterday. Only small amounts of snow fell near Banner Summit, but I'd expect those amounts to increase to the north and west. Any small fresh wind slabs that formed overnight will be easy to trigger. Conditions will be trickiest where these problems overlap at upper elevations and on wind-affected middle elevation slopes.

Regioni coperte