Avalanche forecast

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Avalanche danger

Wed
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

A large, natural avalanche failed in this zone overnight on Sunday. Ongoing wind-loading and layers of weak snow continue to create dangerous avalanche conditions and human-triggered avalanches are likely on wind-loaded slopes.  Avoiding steep slopes—especially those exposed to the wind—will help you stay out of trouble. While unlikely, we can't rule out triggering a very large, 3-4 foot thick avalanche—especially on very steep, rocky, wind-affected slopes.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Strong, gusty winds have been blowing since Friday, scouring some slopes and building stiff slabs on others. This wind has been responsible for a cycle of avalanche activity across our area:

    • Yesterday, a large avalanche was reported in upper elevation terrain in the southern Sawtooths. It likely failed overnight on Sunday. 
    • Also yesterday, a large avalanche was reported on Griffin Butte, near Ketchum. It failed sometime this weekend.
    • Sunday, a group of riders in the Soldier Mountains triggered a 1-2' thick wind slab on a south-facing slope at 7,500'.
    • I was in the Sawtooths yesterday and found several recent wind slabs in middle elevation terrain (photos here and here).
    • Chris was above Prairie Creek on Saturday and watched the wind rapidly loading a SE-facing slope. He remotely triggered a small(ish) wind slab avalanche from about 50 feet away (video at right/above).

    Strong winds build slabs in locations where you might not usually find them, as I found in the Sawtooths yesterday. Wind slabs will be most common in upper elevations, but are possible on mid elevation slopes as well. From an avalanche danger perspective, the larger concern is still the additional loading on the persistent weak layers described above. Even small wind slabs can be great triggers for more deeply buried weak layers. Any avalanche that steps down to these persistent weak layers will be large and destructive.

    ADDITIONAL DISCUSSION: The ongoing wind event is moving plenty of snow and there has been some significant cornice formation in the past few days. Sunday, I found large, fresh cornices in the Banner Summit Zone that were easy to trigger. Yesterday, I spotted several large, improbable cornices threatening slopes in the Sawtooths. As the wind continues, these cornices will be failing naturally, tumbling down the slopes below. These dense blocks can penetrate deeply into the snow as the cartwheel downslope, providing a great trigger for buried weak layers.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    Our snowpack is plagued by two prominent persistent weak layers:

    1. Facets and isolated surface hoar buried 1-2' down: The train of storms that brought significant snowfall across our region buried a weak layer that has produced avalanche activity in all of our zones. It was the likely culprit in a remotely-triggered slide in Beaver Creek last weekend. Thanks to the nature of these layers and the ongoing wind-loading, triggering an avalanche on these layers is likely today. These layers are probably the culprit weak layers in some of the recent avalanches described in the wind slab section below.
    2. December facets, now buried 3-4' down: As this layer becomes more deeply buried it becomes harder to impact. Obvious signs of instability (like collapsing of the snowpack) become less frequent, the first sign of instability may be a large, unsurvivable avalanche. Unfortunately, it has shown few signs of healing. This layer is trending towards a deep persistent slab problem: difficult to trigger with terrible consequences if you do.

    We are in the midst of a multi-day wind event that is producing strong W to NW winds. These winds are loading many slopes at middle and upper elevations, keeping these weak layers on edge. Avoiding slopes over 35 degrees that have been affected by the wind will greatly reduce your chances of triggering a persistent slab avalanche. Keep in mind that these slides can be triggered remotely—from below, above, and to the sides of steeper terrain.

    (1/31/2021) Debris from an avalanche that was remotely triggered in the Beaver Creek drainage last Sunday. The crown is up to 3 feet thick and the slide was triggered from 100 feet away.

Avalanche Discussion

I'm going to give you two discussions today, one about wind and snow and one about you and me. There is a lot in here, but I think it is all important. If you've got a few spare minutes pour yourself another cup of coffee and give them both a read.

WIND AND SNOW When we think about the primary factor that is affecting the snowpack are often thinking about storms and snowfall. However, during prolonged wind events (right now), the wind can be a major driver of both avalanche activity and snowpack variability. Over the past 5 days, strong winds have scoured many slopes and created stiff drifts on others. Take a look at this photo I took in the Sawtooths yesterday to get a sense of this. In the upper portion of the image, you can see slopes that have been scoured down to an icy sun crust. In the lower portion, you can see stiff dunes of snow that were deposited by these strong winds.

When the wind blows like it has been, it creates unusual loading patterns. We are used to seeing softer slabs near ridgetops when we think about wind slab problems, but prolonged strong winds can create slabs in places where you wouldn't normally find them (photo here). Hard slabs, like those that have been building, are unpredictable. They are so stiff that they can easily support our weight in many places, making it more difficult for us to impact layers of weak snow underneath. But when we find thinner spots in the slabs, or the edges of the slabs where they taper down, we can trigger slides that propagate long distances, thanks to the stiffness of the slab. 

To add complexity to this picture, remember that this is all taking place on top of a snowpack with multiple proven weak layers. Some of these layers are widespread and some are more isolated. Some have been with us for months and others are new players in the game. Is this all starting to sound complex? I think that is good, the backcountry snowpack is mind-bogglingly complex. Speaking of complex... let's look at what happens when we add humans to the picture. 

YOU AND ME: OUR OWN WORST ENEMIESSince January 30th, 16 people have lost their lives in avalanche accidents in the U.S. This was the deadliest avalanche period in our country in over 100 years. While that is a terrifying, heart-wrenching statistic, the people who lost their lives aren't statistics. They are brothers and sisters, sons and daughters, each with countless loved ones that will never get to see them again. Don't just gloss over this, take a minute to let it sink in.

When we enter avalanche terrain in the backcountry we are playing a dangerous game, one with high stakes and small margins for error. Faced with the harsh realities of the backcountry environment it is easy for us to find ways to explain away these dangers. We do this without even thinking about it, it is a defense mechanism that our brain employs to help us feel comfortable with our choices. We are story-telling animals. We tell ourselves stories that help us to make sense of the world around us. Unfortunately, the stories that we tell ourselves don't always reflect reality.

If you have been backcountry riding or skiing for very long I can guarantee that you have made some bad choices in the mountains. I know that I sure have. If you don't think you have, I suggest you spend some time reflecting on your past experiences. This isn't an indictment of you or me, it is an invitation for us to reflect on our good luck and to learn from it. We learn very little when we think we already know everything. The backcountry environment is a feedback-poor one. Oftentimes when we make bad decisions we don't get any negative feedback from them, just good powder skiing and riding. But that isn't a sustainable way to travel through the mountains. One way to give ourselves more feedback is to do a "debrief" after a day out in the mountains. You don't have to be a snow professional to do this, everyone can benefit from this simple exercise. Here are a few questions you can ask your group to help get the ball rolling:

  • Did we establish a plan in the morning? Did we stick with the plan we established? If not, why did we change the plan?
  • What was the most hazardous portion of the day? Was this a hazard that we anticipated? How did we manage this hazard?
  • Did we find conditions that we anticipated or were things significantly different? Did this cause us to change our initial plans?
  • Did we have any near misses (points at which the day could have gone drastically differently?)

I've spent much of this season worried about my close friends and the people I love who spend lots of time in the backcountry. I've spent much of the season worried about you all as well. I feel incredibly fortunate that we haven't had any serious accidents in our area this season and I hope that the trend continues for us. I know that part of the reason for that is because you have been making good decisions and part of it is because we get lucky sometimes. Waiting out bad persistent weak layers, and sticking to mellow terrain during prolonged instability, requires discipline and patience. Stay the course my friends, there will be times with good stability and steep powder but we aren't there yet. Thanks for reading, and thanks for making good decisions in the mountains. And do me a favor and try a debrief next time you go skiing. Lets keep learning and keep having good days in the mountains

Regions covered