Avalanche forecast

Rattlesnake

West Central Montana Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 3 years ago.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

Highlights

Avalanche danger will increase throughout the day as another round of snow arrives. Human triggered wind slab avalanches are possible in the new snow at upper elevations. 

Look for cracking around your skis or snowmobile, and use test slopes to look for fresh slabs in the new snow. If you find these, step back to slopes under 30 degrees. 

 

Avalanche problems

  • Wind Slabs

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

    New snow combined with moderate to strong east winds has built fresh wind slabs on west facing slopes and cross loaded complex terrain. These wind slabs will be sensitive today, and human triggered avalanches are possible.  

    Expect to find wind slabs along ridgelines, in gullies, around rocks, and on convex rollovers. 

    Wind slabs can often be identified by their smooth, rounded appearance. If the snow feels hollow under you, this is also a good indicator of wind slab. Avoid the problem by sticking to sheltered or wind scoured areas.  If you encounter sensitive wind slabs or are seeing red flags like cracking and collapsing, stick to slopes under 30 degrees.

  • Persistent Slabs

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

    Triggering a large persistent slab avalanche at upper elevation is a low likelihood, high-consequence scenario. It has been two weeks since the last avalanche on these layers, but the poor snowpack structure remains. 

    Dealing with this problem is an individual risk tolerance question.  Use slope angle if you want to avoid the problem completely. Large persistent slab avalanches are even more unlikely on slope angles 30 degrees or under. 

Avalanche Discussion

Last night snow underperformed, and less snow fell than was expected. New snow totals in Seeley and the Rattlesnake are just a few inches. This brings new snow totals up to 9 inches since our last forecast on the 11th. Ridgetop winds have picked up since 8 pm last night and have remained steady in the strong category out of the east. 

Today, snow is expected to continue, with another pulse of moisture arriving this afternoon. If today's new snow is on the higher end of the forecasted range, avalanche danger could push towards considerable by evening. 

This new snow is not falling on a weak layer in the top portion of the snowpack and is expected to bond well with the old snow. Wind slabs will be the primary concern in the Rattlesnake and Seeley zones, where atypical east winds will blow snow onto west aspects, forming wind slabs. 

What about the persistent slab problem? Why is it still on the forecast if it is unlikely? Even though we have not seen an avalanche on these deeper facets in two weeks, we are still uncomfortable with the poor snowpack structure and the potential for a large avalanche to surprise someone. How much you are willing to expose yourself to this problem is a matter of personal risk tolerance. Be aware that any avalanche triggered near the ground will be large and potentially catastrophic. 

Let us know what you are seeing by submitting an observation.

Ski and ride safe. 

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