Avalanche forecast

Banner Summit

Sawtooth Avalanche Center
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Avalanche danger

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

You're most likely to trigger an avalanche in areas with stiff drifts or slabs near the snow surface. These slabs have the potential to break down to buried weak layers, causing a very large, destructive avalanche. Natural and human-triggered loose snow avalanches are possible on very steep slopes.

Avalanche problems

  • Wind Slabs

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

    You could trigger soft wind slabs up to 3 feet thick in exposed terrain. Tuesday's heavy snowfall and wind formed slabs near upper elevation ridgelines and possibly in some middle elevation terrain. Look for fresh cornices, dunes, or rippled snow surfaces; these are clues that the wind has been at work. Cracks shooting out in front of your skis or boards, mean you've probably found a wind slab. 

    Cornices have grown substantially this week, and the most recent growth may be very soft; natural or human-triggered cornice fall can trigger wind slabs beneath cornices. Give large or overhanging cornices a wide berth.

  • Persistent Slabs

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

    Triggering a large, destructive 3-6 foot thick avalanche is possible. These slides will fail on persistent weak layers (crusts, crusts and facets, or facets) in the middle or bottom of the snowpack. You're most likely to trigger one of these beasts in steep, rocky, wind-swept alpine terrain and in the northeastern corner of this zone. Here, thin areas of the snowpack make it easier to trigger avalanches.

    Persistent Slab avalanches can release in surprising ways. You can trigger them from flat or low-angle terrain long distances away from steep slopes, and they can break far above you. They can break hundreds or thousands of feet wide. Before triggering an avalanche, you probably won't experience snowpack collapsing or other obvious signs of instability. 

     

    (3/3/2024) The crown of this large avalanche near Valley Ck Lake north of Stanley is an estimated 3-5 feet tall. It probably involved persistent weak layers and failed on a NW-W aspect near 8900'. In the northern mountains, these large persistent avalanches are most likely where the snowpack is thinner: in the eastern side of the Banner Summit zone and the far northeastern corner of the Sawtooth & W Smoky zone (NE of HWY 21). Photo: Sena Strenge

  • Loose Dry

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

    Natural or human-triggered sluffs could be big enough to knock you over or bury you. Natural loose snow avalanches are most likely on very steep, rocky, wind-sheltered terrain soaking in the sun. Human-triggered sluffs may also occur on very steep, shaded slopes. Most of these slides will be small and relatively harmless; however, large slopes, chutes, and couloirs could produce powerful sluffs that could easily catch, injure, or bury people. Don't underestimate the power of these slides. Be aware of the terrain above you and where an avalanche could carry you.  

    (3/6/2024) Loose snow avalanches (sluffs) caused by warming from the sun. Photo: Sun Valley Heli Ski

Avalanche Discussion

Yesterday's clear skies allowed us to have a good look around. Large to very large avalanches were observed on various aspects in the Sawtooths, Smokys, Boulders, Soldiers, and the mountains around the Wood River Valley (Avalanches). Some of these slides appeared quite crisp, releasing at the tail end of Tuesday's storm. Many broke hundreds to thousands of feet wide, involving one of the multiple weak layers of snow buried in the snowpack. Most of these occurred in wind-drifted, alpine terrain.

Avoiding slopes with stiff drifts or slabs near the snow surface is the best way to reduce your odds of triggering a large avalanche.  As you climb into winder terrain you'll find recently formed wind slabs and variably thinner snowpack areas where triggering a Persistent Slab avalanche is more likely. 

Although cool, today's wind will be calmer than yesterday. This will encourage some steep, rocky, slopes to shed their recent snow. Avoid lingering beneath these slopes, especially as crusts soften this afternoon. 

Regions covered