Boletín de aludes

Bitterroot

West Central Montana Avalanche Center
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Peligro de aludes

Sun
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 2 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Periods of sunshine today will cause the surface snow to heat up and lose strength quickly. Triggering wet loose avalanches will become possible in sun-affected terrain. Watch for signs of instability, like rollerballs, point releases, or fresh wet snow avalanches. If you see these, it is time to exit avalanche terrain or move to shaded slopes. 

Lingering wind slabs are possible along ridgelines, especially on east aspects. If you see cracking around your skis/snowboard or find a firm slab at the surface, stick to slopes under 35 degrees in slope angle. 

Problemas de aludes

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    6-12 inches of new snow from the past week sits on top of a stout crust. It won't take much sun for this snow to become wet today and slide, especially with the smooth bed surface below. Most sunny aspects will have a thin melt-freeze crust at the surface this morning, but it will break down quickly once the sun comes out. 

    The typical progression of wet loose avalanches involves rollerballs, and small point releases, leading to larger wet loose avalanches. If you encounter rollerballs or small wet loose avalanches, expect larger ones to follow. Remember that even small avalanches can have serious consequences in consequential terrain. 

    If you find yourself in mushy, wet snow or see natural, wet loose avalanches, it is time to step back out of avalanche terrain and be aware of what terrain is above you. You can also move to cooler, shaded slopes to find drier snow.

    (3/20/2024)

    Several natural wet loose avalanches on the southeast side of Murphy Peak. 

    Photo: Arden Feldman

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    Light winds over the past week drifted recent snow into soft wind slabs along ridgelines, especially on east aspects at the highest elevations. Over the last two days, observers noted cracking around their skis in their travels at upper elevations but no avalanches. Today, expect to encounter lingering wind slabs that are still possible to trigger, although decreasing in sensitivity. 

    Wind slabs can often be identified by their smooth, rounded appearance and often form along ridgelines, in gullies, behind rocks, or on convexities. If you encounter cracking around your skis or snowmobile or see recent wind slab avalanches, step back to terrain with a slope angle under 35 degrees.

    (3/28/2024)

    Cracking in fresh wind slabs along upper elevation ridgelines. 

    Photo: Arden Feldman

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely
    Tamaño
    1.5–2.5

    Persistent slab avalanches remain unlikely, but high consequence if triggered. The primary layer of concern is weak snow surrounding a crust in the middle of the snowpack. This problem has been unreactive and not producing avalanches, except for one avalanche in the southern Bitterroot on March 12th, which resulted in a fatality.

    You will not see red flags like cracking, collapsing, or whumfing before triggering an avalanche. Slopes with previous ski tracks are still suspect, and it is possible that the second or third skier on the slope could trigger the avalanche. The only way to identify this problem is to dig in the snowpack. If you find a crust with a thin layer of weaker snow above or below it and a slab above, recognize the potential for a larger avalanche. If you want to avoid the issue completely, avalanches are unlikely on slopes under 30 degrees in slope angle.

Avalanche Discussion

Spring conditions can be tricky. The increased sun angle can quickly heat the snow and can cause more unpredictable storms. Conditions can change quickly, with several avalanche problems occurring simultaneously, as we see today. 

With periods of sunshine in the forecast, wet snow avalanches are the primary concern today. The new snow at the surface will heat up quickly and lead to wet loose avalanches moving easily on the smooth bed surface below. Wet slab avalanches are unlikely, but isolated areas that still hold wet snow in the middle of the snowpack could still produce a wet slab. Or, if the new snow at the surface becomes fully wet, a surface wet slab is possible. 

Dry snow avalanche problems also remain a concern. Lingering wind slabs are possible at upper elevations, and as you come off ridgelines, you could find isolated storm slab instabilities. Periods of graupel over the last few days may have also pooled at the base of cliffs and steeper rock bands, and built isolated slabs. If you see cracking in the new snow or it feels slabby under you, avalanches are possible. Persistent slabs are unlikely, but if you find an isolated area with poor snowpack structure, consider the consequences of a large and destructive avalanche.  

Unfortunately, the time has come for the avalanche center to begin wrapping up operations for the 23/24 season. Thank you for another great season! Our last forecast of the season will be issued on March 31st, 2024. On April 1st, we will issue a General Avalanche Information product with general spring backcountry travel advice. 

Unlike our Forest Service neighbors, we are a nonprofit avalanche center, and we do not have the resources to continue producing avalanche forecasts later in the spring. Please consider donating if you value our work and would like to see us grow and improve our products in the future. We’re already looking forward to next season - let’s hope it’s snowier than this one!

Please continue to submit observations even as our forecasting season comes to an end. The information helps us wrap up our season and provides valuable information for those continuing to get out this spring. 

Ski and ride safe!

 

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