Bulletin d’avalanche

Bitterroot

West Central Montana Avalanche Center
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Danger d’avalanche

Mon
Alpin
1 · Faible
Limite forestière
1 · Faible
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Avalanche conditions are generally stable today except for small wet loose avalanches on steep sun affected slopes. If you find wet, mushy snow, avoid avalanche terrain or move to cooler, shaded slopes. If you decide to step out to steeper terrain today, remember to use safe travel practices, like riding one at a time. 

Fresh wind slab avalanches will develop at upper elevations and along ridgelines this evening as a storm impacts the region overnight. 

Problèmes avalancheux

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    Small human triggered wet loose avalanches are possible on sun affected slopes today. 

    Observers reported small wet loose avalanches on steep south aspects during the last few days. Today, wet loose avalanches will be less widespread due to increased cloud cover and moderate southwest winds. However, some middle and lower elevation slopes may have only partially refrozen overnight. Temperatures dropped just below freezing in most mountain locations, but they are significantly warmer than previous nights. Daytime high temperatures are forecast to be cooler than yesterday, in the upper 30s and low 40s. 

    After a couple of warm, sunny days, most solar-affected areas have some form of surface melt freeze crust. Today, that crust must break down before the snow can lose strength and lead to wet loose avalanches. The typical progression of wet loose avalanches involves rollerballs, and small point releases, leading to larger wet loose avalanches. Remember that even small avalanches can have serious consequences in consequential terrain. 

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

    (3/8/2024)

    A skier triggered small wet loose avalanche on an upper elevation south aspect on Sanders Peak in the Rattlesnake. Although it was small, it was easily large enough to knock you off your feet. 

    Photo: Arden Feldman

Avalanche Discussion

Generally stable conditions exist today, with the exception of small wet loose avalanches and small wind slabs developing tonight. Remember, low danger does not mean no danger. There is some uncertainty about how wet the snow will get today and how solid last night’s refreeze was at middle and lower elevations. The danger could reach moderate in isolated areas this afternoon if the sun is stronger than forecast. This is most likely to occur in the Southern Bitterroot, where the clouds are forecast to be thinner. Additionally, last night’s increased west winds may have formed some small new drifts to watch out for today. 

Tonight, a cold front will deliver 3 to 7 inches of snow, favoring the Bitterroot. Moderate southwest winds will drift the new snow into small wind slabs at upper elevations and along ridgelines. If you are out this evening or overnight into tomorrow, stay alert for cracking and pillowy-looking fresh wind slabs. 

We removed the persistent slab problem and the older wind slab problem yesterday. Triggering a slab avalanche has become very unlikely, and neither issue reaches the threshold to be included as a full avalanche problem. However, this does not mean they are no longer of any concern. Isolated and stubborn wind slabs may still linger in the highest terrain. Also, the poor snowpack structure that we have talked about for months did not suddenly disappear. The poor structure remains on some upper elevation slopes, especially those facing north and east. However, the buried weak layers have gained significant strength over the last few weeks and have been tested by several strong storms with minimal resulting avalanches. 

With a large enough trigger, like a cornice failure, it may still be possible to trigger a large slab avalanche. In the last week, we have observed a couple of large avalanches that failed in that way. Stay heads up around large, overhanging cornices and steep, rocky, or noticeably shallow slopes. 

If you encounter any signs of instability, like cracking or collapsing, consider stepping back to lower-angle terrain. Additionally, if you dig down into the snow and find a poor snowpack structure with softer snow around hard crusts, or loose sugary snow below a firmer slab, recognize the continued potential for a large and dangerous persistent slab avalanche. You can reduce your exposure by sticking to slopes free of terrain traps and without rollovers or convexities. Couloirs, chutes, long avalanche paths, cliffs, and exposed rocks or trees increase your risk. If you decide to step out into steeper terrain, be sure to use safe travel practices, such as riding one at a time and regrouping in safe zones.

Please let us know what you see out there today by submitting an observation. 

Ski and ride safe! 

Régions couvertes