Avalanche forecast

Banner Summit

Sawtooth Avalanche Center
View on map

Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
Open full map
Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

You may be able to trigger avalanches large enough to bury a person at upper elevations and on some middle-elevation slopes facing W-N-E. You may or may not observe obvious warning signs like snowpack cracking or collapsing before triggering a slide.

Avalanche problems

  • Persistent Slabs

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

    You could trigger 1.5-2.5 foot thick avalanches that fail on buried persistent weak layers near the base of the snowpack. Weak layers exist on upper elevation slopes and most middle elevation slopes facing W-N-E. You'll find a stack of weak, sugary facets on shadier slopes and on sunnier slopes, a variable series of crusts and facets.

    You'll most likely find trouble where the slab above the weak layer is strong. The strength of the slab will vary from slope to slope (see video at right/below). You've found a strong slab if pushing your ski pole to the ground is difficult. A strong slab will also likely support your weight if you hop off your machine or step out of your skis.

    You may or may not observe obvious signs of instability, like cracking and collapsing of the snowpack. Tracks on a slope are not indicators of stability—avalanches may be triggered after many riders have crossed a slope. The best way to manage this problem is to avoid avalanche terrain where stiff slabs rest above weak, older, facets and crusts. Short of that, you can reduce your risk by avoiding large avalanche paths and those with ugly consequences if you are caught in a slide.

Avalanche Discussion

The odds that you trigger an avalanche are low but not zero. The last reported slab avalanches are estimated to have occurred over two weeks ago (database). While weak layers in the snowpack have only marginally gained strength, the overall stability is improving as we've gone days without a significant storm.

Many soft snow surfaces exist, thanks only in part to recent snowfall. The prolonged drought has faceted the snowpack, even degrading once stiff, alpine drifts into soft, recycled powder. On the plus side, this faceting process has weakened the slab in some areas, limiting its ability to produce an avalanche. The downside is that strong snow over weak snow setups can be harder to identify, masked by softer snow at the surface. 

You'll find weak snow at the base of the snowpack at upper elevations and on most middle-elevation slopes facing W-N-E. These layers are widespread and exist across the forecast area. However, the recipe for a persistent slab avalanche calls for a slab. This key ingredient is found in fewer locations. Monitor the stiffness of the snow you're traveling through. Use your ski pole or hop off of your machine to feel for a strong slab beneath the surface. Stronger slabs are more common in our deeper snowpacks around Banner Summit, the Sawtooths, the W Smokys, and the Soldiers and on slopes that are wind-loaded. Areas that lack a slab can produce loose, dry facet-lanches. While less likely to bury you, these slides can easily knock you off your feet or carry you into unwanted terrain.

Regions covered