Avalanche forecast

Bitterroot

West Central Montana Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
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Out of date — this forecast expired 3 years ago.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

1-2 feet of snow has fallen during the past few days, and human-triggered avalanches are possible. Today should be excellent for skiing and riding, but don't let the powder cloud your judgment.

Watch for red flags like shooting cracks and recent avalanches. If you encounter these, step back to slopes under 30 degrees in slope angle. Storm snow instability is short lived, and by tomorrow, much of the instability will have passed.

Avalanche danger is close to considerable at the upper elevation in the southern Bitterroot and Seeley Lake zones, where new snow totals are higher.

Avalanche problems

  • Storm Slabs

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

    Storm slabs are possible today at mid and upper elevations. Storm slabs are likely in areas like the southern Bitterroot that received more new snow last night.

    In the southern Bitterroot and Seeley Lake zones, 1-2 feet of snow has fallen during the past few days. In the northern Bitterroot, new snow totals are significantly less, and as a result, storm snow avalanches will be smaller.

    Expect storm slabs 1-3 feet deep, with isolated deeper slabs at upper elevation and leeward terrain. Human triggered avalanches are possible and may be triggered remotely from above, the side, or below.

    Test slopes are an excellent tool for identifying potential storm slab problems.  Shooting cracks and recent avalanches are red flags that you will likely trigger an avalanche on larger slopes. 

    Storm slab sensitivity is usually short-lived. If you encounter red flags or avalanches, you can reduce risk significantly by waiting a day before moving onto slopes steeper than 30 degrees.

    Photo: Cam Mackenzie

  • 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 with a slab over weak, sugary snow.

    Dealing with this problem is an individual risk tolerance question.  Use slope angle if you want to avoid the problem completely by sticking to slopes under 30 degrees.

Avalanche Discussion

Today is looking to be an excellent day for skiing and riding. Winds will decrease throughout the day today, and skies will be clear by evening. 

New snow since the 11th

Seeley Lake NF Jocko: 17 inches

Rattlesnake Stuart: 9 inches 

Bitterroot Lolo Pass: 9 inches

Bitterroot Twin Lakes: 7 inches 

Bitterroot Saddle Mountain: 10 inches

Our weather stations are few and far between, and SNOTEL data and field observations have not lined up well. Weather stations sometimes reported just a few inches, while field observations reported a foot or more of new snow. If you are in the field and noticing conditions different from what was forecasted or reported, please let us know. It helps fill the gaps where we have missing or incorrect weather data. 

Instability from this storm will be short lived. If you encounter red flags or avalanches today, step back and try again tomorrow. There is a good chance that much of the storm snow instability will have settled in that time. 

Except for the Rattlesnake, most of our forecast zones were sheltered from strong east winds the past few days and as a result, wind slab is the primary problem in the Rattlesnake. That does not mean other areas didn't get clipped by some east winds, particularly along the Swan crest, where isolated wind slabs could be lingering.

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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