Avalanche forecast

Banner Summit

Sawtooth Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 3 years ago.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

Highlights

Triggering a large, destructive avalanche is possible. You may not see any signs of danger before triggering a slide. These avalanches could be triggered from long distances away from steeper slopes. Smaller avalanches involving only the past week's snowfall are also possible. 

Avalanche problems

  • Persistent Slabs

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

    Triggering a wide, 2-4 foot thick avalanche large enough to bury people and possibly destroy a house remains possible. Dense slabs exist on nearly all slopes, and you'll find facets and/or surface hoar on shadier aspects and crust + facet combinations on sunnier slopes.  

    The odds you will trigger a Persistent Slab are decreasing, but the consequences remain severe. Don't expect to see obvious signs of instability, like snowpack cracking or collapsing, before triggering a slide. You may be able to trigger avalanches from flat or low-angle terrain long distances away from steep slopes.

    Sadly, the only surefire way to manage this problem continues to be avoiding avalanche terrain, including the base of slopes that are threatened from above. 

    (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.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    This zone picked up a couple inches of snowfall in the last 24 hours and up to 2 feet in the past week. There are a few "new snow problems" to consider today:

    • You could trigger loose snow avalanches (sluffs) in very steep terrain. If the sun pokes through the clouds today, these slides could release naturally. 
    • Expect to find isolated, small, fresh wind slabs near ridgelines at upper elevations.
    • Observations indicate the past week's snowfall bonded well to the old snow surface on most slopes, but a couple professionals reported questionable snowpack test results and possibly some thinner slabs that failed on this interface. 

    All of these slides could run fast and far on stout crusts beneath the recent snowfall. These avalanches could carry you where you don't want to go and possibly trigger the Persistent Slab avalanches described above.

Avalanche Discussion

We're facing a classic "scary MODERATE" scenario; you're having fun shredding powder in avalanche terrain, you don't see any obvious signs of instability, and then you trigger a huge avalanche. Unfortunately, hearing a story like that would not surprise us. A few things to consider:

  • Under these conditions, it's extremely difficult, if not impossible, to accurately determine whether a given slope is safe to ski or ride. 
  • Areas with thinner snowpacks - less than about 4 feet thick - are more likely to produce avalanches than areas where the snowpack is deeper. Rocky slopes with variable snow depths may allow your skis or sled track to more forcefully impact the weak layers and trigger an avalanche.
  • On the southern half of the compass: The hot, sunny weather in late January produced a soggy upper snowpack on all but the highest elevation slopes. The wet snow formed a stout crust when it froze. While large avalanches are probably more difficult to trigger on SW-S-SE aspects, we cannot rule them out.
  • On the northern half of the compass: The snowpack was not as significantly impacted by the hot, sunny weather in late January.

If you're skiing or riding in avalanche terrain in this zone, think about where an avalanche would carry you before committing to steep terrain. If the mental image of being dragged through trees or buried in a creek makes you shudder, you can always choose to play on gentler or less consequential slopes.   

Regions covered