Bulletin d’avalanche

Bitterroot

West Central Montana Avalanche Center
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Danger d’avalanche

Fri
Alpin
2 · Modéré
Limite forestière
1 · Faible
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 3 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Skiers and riders could trigger small fresh wind slabs on upper elevation north and west aspects today. Look out for shooting cracks and smooth-looking pillows of wind-drifted snow. Avoid wind-loaded slopes over 35 degrees. Additionally, small dry loose avalanches may need management on steep, shaded, non-wind-affected slopes. 

Stay alert for changing conditions tomorrow as a storm impacts the region.

Problèmes avalancheux

  • Wind Slabs

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

    East-southeast winds increased to moderate to strong yesterday evening and likely built small wind slabs on leeward aspects at upper elevations. There is only a small amount of snow available for transport, but it is low-density and easily transportable on shaded slopes. Yesterday, light to moderate southeast winds built isolated drifts along the highest ridges of the Rattlesnake. Today they will likely be more widespread. 

    There is some uncertainty in the spatial extent of last night’s wind event. Typically, these east winds are strongest in the Rattlesnake. However, we can’t rule them out for upper elevations of the Bitterroot and Seeley Lake as well. 

    Any wind slab triggered today will most likely be small and isolated to near ridge tops and along the edges of gullies. However, if you find one of these pockets, it could knock you off your feet and carry you into or over hazards. Stay alert for shooting cracks and smooth-looking pillows of wind-drifted snow. The best way to manage the hazard is to avoid wind-loaded slopes over 35 degrees.

  • Loose Dry

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

    Yesterday, low-density surface snow was sluffing easily on steep slopes. Small dry loose avalanches are possible on steep, shaded, non-wind-affected slopes throughout the forecast area today, especially where crusts underlie the recent snow. Although these avalanches are small, they could knock skiers off their feet and push them into or over hazards. Terrain traps and chutes could funnel these avalanches and make them deeper and more dangerous. 

    The easiest way to mitigate loose dry avalanches is to avoid steeper slopes. If you are skiing steep consequential terrain, manage loose dry avalanches by getting out of their way and letting them run.

Avalanche Discussion

Conditions remained fairly consistent over the last several days with relatively calm and cool weather. Other than small dry loose avalanches to manage in steep, shaded terrain, the snowpack has generally been stable. However, yesterday evening east-southeast winds picked up to moderate to strong at the Point 6 weather station in the Rattlesnake. There will likely be small fresh wind slabs at upper elevations today. 

Unfortunately, the Point 6 weather station provides the only reliable upper elevation wind data in our forecast area. This creates significant uncertainty in the spatial variability of last night’s wind event. These east wind events are typically strongest in the Rattlesnake. However, lacking other upper elevation wind data, we can’t rule out fresh wind slabs in the Bitterroot and Seeley Lake zones as well. We hope to install new weather stations in the future to dial back the uncertainty. Further north at the Flathead Avalanche Center’s Mount Aeneas weather station in the Northern Swan Range, the East winds were strong last night. This points to a potentially more region-wide wind event. 

South aspects crusted over in the last few days. That, combined with increased cloud cover and cool temperatures today, should keep wet loose avalanches at bay. 

Skiing and riding conditions are currently variable. Conditions are better in sheltered, shaded areas and in areas that have received more recent snowfall to cover up old crusts, like the Bitterroot. However, these are the same areas with the potential for bigger loose avalanches. 

Today will be another gorgeous day to get out in the backcountry, but remember that low danger doesn't mean no danger. Continue to practice safe travel, such as skiing one at a time. Check for instabilities before entering steep terrain, and stay alert for red flags. 

A storm is forecast to impact our region tonight through Saturday morning, and the avalanche danger will increase. Stay alert for changing conditions. The forecast is calling for 0.5 to 1 inch of snow water equivalent and moderate to strong southwest winds. Look out for fresh avalanches in the new snow. They will likely be sensitive on the weak old snow surface. Signs of instability, like shooting cracks, warn you to stay off steep slopes. 

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

Ski and ride safe.

Régions couvertes