Avalanche forecast

Rattlesnake

West Central Montana Avalanche Center
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Avalanche danger

Sat
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 6 months ago. You’re viewing past conditions, not the current bulletin.

Highlights

Skiers in this zone triggered reactive slabs in the new snow yesterday. With a foot or more of fresh snow and continuing wind, triggering a wind slab avalanche remains likely in upper elevation terrain today. Sluffing within the new snow is likely, particularly as the day warms. Expect triggered slides to move quickly on crusts under the new snow. Below the new snow, well-defined weak layers exist in the upper 1-2.5 feet of the snowpack. Any slides that break down to these layers will be large, wide, and destructive. Avalanches that start in the new snow may break down to these buried weak layers. 

Avalanche problems

  • Persistent Slabs

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

    Prominent weak layers are buried in the upper 1-2.5 feet of the snowpack. Dig down and you'll find facets, surface hoar, and crust+facet combinations, depending on your aspect and elevation. Last week, during an intense storm, these layers produced a widespread natural avalanche cycle (you can view recent avalanches here). Many slides broke hundreds of feet wide. The largest slides spanned 1,500-2,000' feet of terrain (photo at right/above). These layers became less reactive and harder to impact as the slab above them stiffened, but yesterday's storm is keeping them on their toes

    Avalanches that fail on these layers of weak snow will break widely and will be able to wrap around terrain features. This produces large, unpredictable avalanches with deep piles of debris that you do not want to be in. You can trigger these slides from below or near steep slopes. Completely avoiding this problem includes avoiding terrain threatened from above. 

    Snowpit near Burgandy on an E aspect at 7,500'. The two obvious layers (surface hoar in this location) are the source of our persistent slab problem. 

    (3/3/2026) Photo: Ben VandenBos

  • Wind Slabs

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

    The Rattlesnake area appears to be the big winner from yesterday's storm, both in snowfall and wind. Here, over a foot of snow accumulated in the past 36 hours, accompanied by gusty winds blowing out of the NW-W. Yesterday, a skier near Snowbowl found touchy slabs in the new snow that were easy to trigger and picked up speed quickly. If you are headed for steep, upper elevation terrain, expect to find these slabs and for them to be reactive to your weight. Triggered slabs will run fast and far on the firm snow surfaces underneath.

    Look for wind slabs near ridgelines and midslope features like gullies that slow the wind down and force it to drop the snow it is carrying. Pay attention to the snow you are moving through. If you are suddenly finding much more snow, or if the snow is becoming thicker and denser, you have likely found a wind slab. Cracks shooting out from your machine or your ski tips are clear signs that the slab you found is unstable. Triggered wind slabs will be plenty large to ruin your day, and will be effective triggers for the larger persistent slab avalanches described above as they run downslope. 

    Avalanche in steep, wind-loaded terrain in the Bitterroot Mountains. 

    (2/28/2026) Photo: Ben VandenBos

Avalanche Discussion

The Rattlesnake area appears to be the big winner out of yesterday's storm. A foot or more snow fell along the high terrain in the area, and winds have been blowing at loading speeds out of the NW-W for much of the past 36 hours. If you head into upper elevation terrain, expect to find reactive wind slabs. Yesterday, a skier near Snowbowl found touchy slabs in the new snow that were easy to trigger and picked up speed quickly. Where the wind has been at work, these slabs have only increased in size and distribution since then. 

Wherever you find yourself playing today, you can identify the new snow hazard by paying close attention to how much snow fell, and how much work the wind did. If you are finding a foot of snow and wind drifts 1-2 feet thick, triggering wind slabs will be easy in steep, open terrain. Across the zone, the new snow is resting on a variety of crusts and firm surfaces and triggering loose snow sluffs will be common in steep terrain. If the sun is out and the new snow is becoming wet, these slides will be more reactive and able to entrain larger amounts of snow as they travel downslope. 

Don't let the new snow distract you from the less obvious, harder to identify, but uncomfortably likely persistent slab problem. We are only a week out from an intense storm and a days-long wind event that produced a widespread avalanche cycle (you can view recent avalanches here). In the days since that big storm, the snow settled into a conditional stability. The frequency of cracking and collapsing decreased significantly, and lots of folks were poking into steeper terrain and not triggering slides. Yesterday's storm didn't appear to bring enough snow to tip the balance in the other direction, but it also isn't helping. Keep the persistent slab problem and these buried weak layers at the front of your mind as you move through the mountains today. Triggering a persistent slab remains a real possibility, and any slide involving these layers will be large. You're most likely to trigger one of these in steep, open terrain where recent and past winds built stiff slabs over these weak layers. Any wind slab you trigger has the potential to step down to these buried weak layers, producing a much larger slide.

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