Avalanche forecast

Banner Summit

Sawtooth Avalanche Center
View on map

Avalanche danger

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Out of date — this forecast expired 3 years ago.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

Highlights

Triggering a large, dangerous avalanche is a real possibility. You may or may not see or hear warning signs before triggering a thick, wide slide. These slides can be triggered from gentle terrain above, below, or to the sides of steep slopes.

Avalanche problems

  • Persistent Slabs

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

    The odds of triggering large, Persistent Slab avalanches are decreasing, but the consequences remain severe. Expect to find 1-2.5 foot thick slabs in areas sheltered from the wind. The slab may be twice as thick in terrain affected by the wind. These avalanches have failed on various weak layers: facets and/or surface hoar on shadier aspects and crust + facet combinations on sunnier slopes. Large natural and human-triggered avalanches have occurred on several aspects in recent weeks. Assume this problem exists on all upper and middle elevation slopes and on shadier, lower elevation aspects.

    Avalanches on this uncommonly widespread and fragile layer will break widely and in surprising ways. Don't expect obvious signs of instability, like snowpack cracking and collapsing. Your first sign of trouble may be the destructive avalanche you trigger. These slides can be triggered from long distances away—from flat or gentle terrain below, above, or to the sides of steep slopes.

    ADDITIONAL DISCUSSION: Anticipate small, sensitive wind slabs at upper elevation. Recent snowfall may not bond well to the mix of crusts, facets, and surface hoar where it's landing. Cracking is your first clue that the slab you've found is unstable.

     

    (1/22/2024) The debris of this slide ran into a creek, a lower and mid-elevation terrain trap that is characteristic of the Banner Summit Zone. Terrain features like these multiply the consequences of these slides.

Avalanche Discussion

The brunt of the storm has largely missed this zone and we've had little slab avalanche activity in the past week. Modest recent precipitation and a heavy, dense slab are allowing buried weak layers to slowly gain strength. While the chance of triggering a Persistent Slab avalanche is gradually decreasing, it is not zero. 

Unfortunately, accurately assessing which slopes are still teetering on the edge is quite difficult. You may get away with it. If not, you'll trigger a thick, unsurvivable slide that could span multiple terrain features. This outcome is a real possibility. Entering significant avalanche terrain remains a high-stakes roll of the dice. 

Regions covered