Bulletin d’avalanche

Rattlesnake

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 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

It is possible for skiers and riders to trigger wind slab at upper elevations today. Lower the chances by avoiding wind-loaded terrain over 35º. Wet loose avalanches are possible on southern aspects this afternoon. If the snow is moist and roller balls start, move to lower angle slopes or shadier aspects.

Problèmes avalancheux

  • Wind Slabs

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

    Winds reached 41 mph yesterday and affected multiple aspects at middle and upper elevations by wrapping around terrain features. 

    Today it’s possible for skiers and riders to trigger wind slab at upper elevations, below ridges, and along the edges of gullies. Easterly slopes are the most suspect, but pockets of windslab could be found on north and south aspects as well.  Stay alert for stiff pillows of hollow-sounding snow, wind lips, and cornices, which indicate the presence of wind slab. Shooting cracks are a clear sign of instability. Avoid wind-loaded slopes over 35º. 

    Higher-quality snow can be found below treeline in sheltered areas where wind impact was limited.

     

  • Loose Wet

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

    Wet loose avalanches are possible at middle and lower elevations today. High cloud today should limit the extent of solar warming and loose wet activity. However, if the sun makes an extended appearance and temperatures rise above freezing, small loose wet avalanches are possible. These avalanches will be limited in size but could build enough to push skiers into or over terrain traps. If rollerballs start, it's a sign that loose wet slides are possible, and it’s time to avoid steep sun-warmed slopes over terrain traps. 

     

Avalanche Discussion

Since the last forecast, around 4" of snow has fallen in the Rattlesnake and Seeley lake area. Lolo pass received 6", Twin lakes 12", and the southern Bitterroot 4". Observations noted over 20" of fresh snow above 8000' in the central Bitterroot, yesterday. 

Winds were cranking in the Rattlesnake yesterday, with Point 6 hitting 41mph. The snow was wind affected on multiple aspects as the wind wrapped around terrain features, but wind slab, for the most part, remained thin. Steep easterly slopes likely contain consequential pockets of wind slab. Lines such as The Birthday Chute in Jenny bowl are places to avoid today.

In the Bitterroot, winds did not materialize as forecast, limiting the extent of wind-affected snow to exposed areas near treeline. Large amounts of new snow available for transport increase the potential size of wind slab in the central Bitterroot. Multiple recent wind slab avalanches were noted near ridge line in the Lappi Lakes area. Sluffing will be a problem to manage in steep terrain today. These higher snow totals and recent wind slab activity elevates the avalanche hazard in the Central Bitterroot. The hazard in the southern Bitterroot is lower due to minimal new snow. 

Today mild temperatures and light winds will give windslab a chance to stabilize. It is best to give them some time, and avoid wind loaded terrain over 35º. The freezing level could rise above 5000,' and moist snow is possible on multiple aspects at lower elevations. 

Apart from surface instabilities, the snowpack is generally stable. The exception is a crust facet combo that can be found on upper elevation south aspects in the Bitterroot. It's been noted in the North Fork of Lost Horse and Bass Creek. This layer is not reactive or widespread enough to be listed as a problem, but it is worth investigating before you commit to south facing terrain. Stay alert for red flags such as whumpfing or cracking. 

Please share what you see in the backcountry by submitting an observation; it helps us build a better forecast. 

Ski and ride safe

 

Régions couvertes