Bollettino valanghe

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

Weak layers buried 1-3 feet below the snow surface are capable of producing large avalanches. To significantly reduce your odds of triggering a slide, steer clear of steep terrain that is exposed to the effects of the wind. Small wind drifts and slabs will be forming during today's storm and these may be reactive to your weight.  Small slabs that release can trigger larger avalanches as they travel downslope.

Problemi valanghivi

  • Persistent Slabs

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

    Several weak layers are buried in the upper 1-3' of the snowpack. These layers are capable of producing large avalanches. I went looking for them in this zone yesterday and found them in multiple snowpits (read my observation and see photos). These weak layers vary by aspect and elevation, and the overlapping patterns are complex and hard to decipher. In this zone, these layers appear to be most reactive on slopes that face the sun, where crusts with facets on top exist. However, I received unstable snowpack test scores on both sunny and shady slopes yesterday. Crusts, facets, surface hoar—it's a safe bet that one or more of these layers exist on most slopes.

    These layers are capable of producing large avalanches, but the likelihood of triggering a slide is gradually decreasing. Unfortunately, the structure for producing these slides (slab + weak layer) remains. Want to avoid triggering a large avalanche today? You can significantly reduce your risk by steering clear of steep, wind-affected terrain. 

    ADDITIONAL DISCUSSION: Weak snow makes up the base of the snowpack here. In most places, it is buried beneath a thick, dense slab of snow, and impacting it with your weight is unlikely. However, the two large avalanches triggered by skiers in this zone in the past 8 days are proof positive that this weak snow should remain on your radar. You are most likely to trigger an avalanche involving this snow in steep, rocky, wind-affected terrain where the slab over this weak snow is thinner and the weak layer is more "accessible". Smaller slides can break down into deeper weak layers, producing a larger, more destructive avalanche.

    (12/31/2022) This large avalanche was remotely triggered from hundreds of feet away on 12/31. It failed on a S-facing slope at 9,500' near Mushroom Ridge, which is near Galena Summit.

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Wind slabs will form during today's storm. Precipitation starts around noon, and by sunset we can expect 3-6" of new snow. Southerly winds will build slabs that may be sensitive to your weight, thanks to the weak snow surfaces they will build on. Pay attention to how much new snow is falling if you are out late in the day and look for textures (drifts, dunes, pillows, ripples, etc.) that indicate that the wind has been at work. Cracks shooting out from your skis or machine are great indicators that you've found a reactive slab. 

    Older generations of wind slabs have largely had time to bond. However, you may still find unstable drifts and slabs in alpine terrain where these slabs are resting on slick, icy, faceted surfaces. This is the same terrain where you are most likely to trigger one of the persistent slabs described above. Small triggered wind slabs can be effective triggers for the weak layers described above (photo at right/above).

    (1/3/2023) These avalanches happened on Galena Peak on 1/3. The avalanche on the left started out as a wind slab and then broke down to deeper weak layers in the steeper, rocky terrain near the cliff band. When smaller avalanches trigger slides on deeper weak layers as they travel downslope it is known as "stepping down".

Avalanche Discussion

MODERATE Danger and Persistent Slab Problems

The Avalanche Danger scale is a tool we use to communicate with our users (you). It is an admittedly imperfect tool. The hazards posed by our snowpack today are a great illustration of this. As time passes without a major loading event, the weak layers in our snowpack have some time to gain a bit of strength, which decreases your odds of triggering a slide. Because of this, the danger has decreased to Moderate. Sounds good, right? Well, yes and no. Read on. 

Today, if you choose to enter avalanche terrain, it's more likely than not that you won't trigger a slide. However, the possibility of triggering a slide remains. This possibility is driving my terrain selection in the backcountry, and the terrain selection of both professionals and experienced backcountry travelers alike. How you choose to deal with this problem is entirely up to you and your level of risk tolerance.

Would you like to avoid triggering an avalanche today?  Simple: avoid avalanche terrain and terrain exposed to hazard from above. Maybe you don't care whether or not you trigger an avalanche large enough to bury you and your partners? Well, that's your choice, enter all of the avalanche terrain you want and prepare yourself for the potential consequences.

Things get much harder when you find yourself somewhere in the middle, as most of us do. Do you find yourself in this category? Welcome to the club. We want to ski and ride steep powder, but we also want to go home to family and friends at the end of the day. You can significantly reduce (but not completely eliminate) your risk by avoiding very steep slopes that are exposed to the effects of the wind. Spend some time thinking about what it would look like if you do trigger a large slide in the terrain you are in. Will you be pulled through trees at high speed or buried deeply in a terrain trap at the bottom? Or is the runout of the slope you are on cleaner and more gradual? We can reduce our risk by thinking about these things and using them to inform our terrain selection. However, if we choose to enter avalanche terrain we are "playing the game" and we should be honest with ourselves about the potential outcomes. 

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