Avalanche forecast

Tetons

Bridger-Teton Avalanche Center
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Avalanche danger

Tue
Alpine
4 · High
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Up to 2 feet of new snow in the last 48 hours, favoring the NW portion of the zone, will create very dangerous avalanche conditions. Fresh wind slabs up to 3 feet deep formed by strong NW to SW winds of 40 mph will be sensitive to triggering. Use cautious route finding as natural avalanches are likely in the upper elevations and ride low angle terrain during this storm cycle as continued snowfall with strong wind throughout the day increases avalanche danger to high.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1–2.5

    Wind slabs up to 3 feet deep are the main avalanche concern as 1-2 feet of new snow combined with strong NW to SW winds create highly reactive slabs in the middle to upper elevations. Slabs up to 4 feet deep are possible in areas such as the NW portion which have received the highest amounts of snow. Wind speed has averaged above 40 mph for the last several hours and will continue today. These slabs lie on a variety of surfaces formed prior to the storm including crusts, wind-pack, and near surface facets. Use extra caution today as slabs formed above these layers are notorious for increased reactivity with the possibility of remote triggering above, below or beside you. Snowfall will continue during the day, increasing their size and reactivity. Look for obvious signs of instability such as cracking, stiffened surfaces, and firm drifts. 

    Storm slabs may also be a concern as snowfall continues throughout the day. These slabs will be possible to trigger in the low to middle elevations. 

  • Persistent Slabs

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

    Increased loading of new snow as this storm cycle continues could cause buried weak layers to wake back up and become reactive. The main concern is the Jan 26th layer buried 2-3 feet deep composed of crusts, facets, and a combination of both. Prior to this storm, this layer appeared dormant with little to no avalanche activity. There is a high amount of uncertainty in how this layer will react to the added weight of new snow, but the poor structure is still apparent in snowpits so we cannot ignore the possibility. Our main worry is triggering a wind slab that coud step down to a persistent slab. 

Avalanche Discussion

The Real Storm Hits

Yesterday was the start of a storm event that will produce higher than average amounts of snow in the mountains with radically strong winds. Avalanche conditions will increase dramatically as the main body of the storm continues into Tuesday evening. Wind slabs will be very likely to trigger as the sensitivity and depth of these slabs increase throughout the day, with natural avalanches likely. And this is only the beginning. Today and during the next couple days it will be critical to take extra time to create large margins of safety when venturing into the backcountry. Focus on analyzing slope angles in terrain, identifying wind slabs, and constantly assessing the snowpack during rapidly changing conditions. Remember, conservative decision making is easier to manage during these uncertain times of large storm events. 

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