Avalanche forecast

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

You can trigger avalanches large enough to bury you on many steep slopes. Avalanches will be larger, more destructive, and easier to trigger as you gain elevation and climb into terrain affected by the wind. Much larger avalanches failing on buried weak layers remain uncomfortably likely and can be triggered from long distances away. Loose snow avalanches will release naturally during periods of direct sun and can become large in the steep, rocky Sawtooths. 

 

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2.5

    2-4 feet of settled snow have fallen in this zone since Monday (2.5-3.5 inches of SWE). Head into the mountains expecting to encounter a wide range of problems related to this new snow today:

    SLABS: Large slabs failing within the new snow are likely, and can occur even in sheltered terrain. The size and sensitivity of these slabs will increase significantly as you climb into wind-affected terrain. If the snow you are moving through is anything but fluffy powder, you are traveling through wind-affected snow. Triggered slides will run fast and far on the stiff surfaces underneath, entraining significant amounts of snow and producing large debris piles. 

    LOOSE SNOW: Loose snow avalanches will be easy to trigger on all steep slopes. You can expect to see these slides happening naturally on slopes receiving direct sun. They'll start small but may become large as they pick up speed and material and rocket downslope. Loose snow slides can flank out into slabs, producing larger avalanches. 

    CORNICES: It has been a very windy week and there has been no shortage of snow available for the wind to blow around. Unstable cornices have grown quite large, and are struggling to hang on to their ridgeline homes. Be cautious when you are traveling on ridgelines, cornices will be easy to trigger and can behave in unpredictable ways. Large natural and human-triggered cornice failures will be effective triggers for large avalanches as they tumble downslope.

    Avalanches involving the recent snow will be large enough to bury you. Natural and triggered slides involving the new snow can be very effective triggers for the weak layers described below. Any avalanche that breaks down into these layers will be very large and destructive. 

  • Persistent Slabs

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

    Weak layers in the upper snowpack lie buried underneath this week's snow. Our observations of recent avalanche activity in this zone are limited, thanks to poor visibility. We will know more about these layers once we observe the aftermath of this recent loading event. For today, it's best to assume that these layers exist in most places and that triggering an avalanche on them is likely. The photo at right/above shows a large persistent slab that failed near Baker Creek, in a neighboring forecast zone. 

    Avalanches that fail on persistent weak layers behave in ways that surprise even experienced users. These slides will break wide, wrapping around entire bowls and cirques. You can trigger these avalanches from long distances away from steeper slopes, including from flat terrain below large avalanche paths. Any of the storm snow avalanches described below can trigger these much larger slides. 

    ADDITIONAL DISCUSSION: Deeper weak layers are buried underneath the very dense, 4-5 foot thick slabs that formed from snow in February. Triggering an avalanche on these layers is much less likely, but any slide that breaks on them will be massive. Smaller natural and human-triggered avalanches can step down to these deeper weak layers. Slides that break on these layers can wipe out swaths of mature timber and will be unsurvivable. 

    This photo shows several large to very large avalanches that failed above the Baker Creek drainage, likely overnight Friday into Saturday. The crowns span hundreds of feet of terrain, and are an estimated 3-5 feet deep in places. Getting caught in an avalanche like this and being dragged through the trees below would likely be unsurvivable. This slope faces E-SE at 9,700'.

    Photo: Ben VandenBos

Avalanche Discussion

Today will be cold and beautiful. If you head into the backcountry, you'll find deep stacks of soft powder. You'll also encounter a complex snowpack that just picked up a major load of water from a 3-day storm. Expect to encounter some obvious problems in the new snow, and some less obvious problems involving the weak layers further down in the snowpack. Read on:

The Banner Summit area has tallied 3-4 inches of SWE (3-5 feet of snow) in the past week. The majority of this fell in the last 3 days. This new snow will present the most obvious set of hazards today. You can expect to encounter wind slabs, storm slabs, loose snow avalanches, and unstable cornices in many locations. Expect these types of avalanches to be easy to trigger on many steep slopes. Once the snow starts moving it will be tough to slow it down. Plan on these avalanches in the new snow running fast and far, entraining lots of snow along the way and producing significant debris piles. It will be cold today, but March sunshine is strong. Expect to see a round of loose snow avalanches that follow the sun across the sky.  

Underneath the new snow is where things get more complex. We've seen the snowpacks diverge significantly across the region over the month of February. In this zone, early season weak layers have become deeply buried and our focused has shifted to weak layers in the middle and upper snowpack. Beneath the new snow, you'll find a few variable weak layers that formed in February. These have produced avalanches in many locations, including when this series of storms started last week (photo here). Avalanches that fail on these layers will behave differently than the "simple" new snow problems described above. They will break widely across slopes and can wrap around terrain features to neighboring pieces of terrain. You can trigger these slides from a long distance away from steeper slopes, including from above, below, and to the side. Slabs at fail on the layer at the base of the new snow will have 3-4 inches of water in them. Avalanches that break down to the early February weak layer will have 6-7 inches of water in them. Any avalanche that fails on these layers will be large and destructive, producing enough debris to snap mature trees and damage houses. 

Today is a great day to build wide safety margins into your travel plans. We are only a day out from HIGH danger and Avalanche Warnings. There are stacks and stacks of deep powder out there, and many places you can enjoy that snow without exposing yourself to avalanche hazard. Make a conservative travel plan and stick with it today. 

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