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 3 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Skiers and riders could trigger wind slab on upper elevations east slopes today. Limit the chances by avoiding wind-loaded slopes over 35º.  Choose planar slopes free of terrain traps to limit the risk of loose dry avalanches.  Where there is 8" or more new snow, choose lower angle slopes.

Problemas de aludes

  • Wind Slabs

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

    At upper elevations, wind slab could be triggered by skiers and riders on east aspects, below ridges, and along the edges of gullies. 

    Today's wind slab could be large and capable of burying skiers and riders, especially at higher elevations where winds were stronger. Terrain traps such as gullies increase the risk of burial. 

    Windlips and cornices indicate wind transport and wind direction. Smooth pillows of snow that may be stiff and hollow sounding indicate the presence of windslab, and shooting cracks are a sign of instability. 

    Avoid triggering wind slab avalanches by avoiding wind-loaded slopes over 35º.

  • Loose Dry

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–1.5

    Up to 12” of low-density snow blankets the forecast area. Yesterday small wind slab in the Rattlesnake was triggering loose dry slides, entraining snow, and running fast and far.  Loose-dry avalanches are possible throughout the forecast area today, especially where crusts underlie the new snow. They could knock skiers off their feet and push them into or over hazards. If encountered in a terrain trap such as a chute where they are funneled and increase in depth, they could result in burial. 

    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.

    Clouds should limit warming today; however, loose wet slides are possible if they do part. If roller balls and pinwheels start, it’s a sign that loose wet avalanches are possible. Move to shadier or lower-angle slopes. 

Avalanche Discussion

Since the last forecast, the snowpack has received a nice refresh. From north to south, the forecast area has received roughly:

  • Seeley 6”
  • The Rattlesnake 8”
  • Central and northern Bitterroot 6”-12”
  • Southern Bitterroot 3”

Yesterday, winds were moderate and predominantly out of the west with strong gusts. Outside of wind-affected areas, the snow remained unconsolidated. Instabilities were limited to windslab and loose dry avalanches. 

One observation noted patches of buried surface hoar on Mt. Fuji, where it is common and likely isolated in distribution. In the Elk Meadows area and in the central Bitterroot, observers noted good bonding of the new and old snow and lack of surface hoar. If you dig and notice stripes of lower-density snow, dial back slope angles. 

Today temperatures climb to the upper 20s at upper elevations; winds are light out of the south. Loose snow could begin to consolidate with the mild temperatures. Skies are forecast to be mostly cloudy, so rapid warming should be limited. However, if you notice the density increasing, watch for cracking, stick to slopes under 35º, and avoid convexities. The presidents day crust, where it exists, is buried up to 12" deep and could be a sliding layer for developing slabs. Increase caution in areas where the new snow exceeds 8" in depth.

Cornices grew with wind and snow over the past two days. Observers noted one natural cornice fall that entrained new snow and ran long distance. Today, stay well back from the tops of cornices and avoid spending time below them. They can break unexpectedly and farther back than anticipated. 

We’re lucky in this area, with instabilities limited to the new snow. The amounts we received can still be consequential, especially when drifted into wind slab, or combined with terrain traps. Approach slopes cautiously today and keep an eye out for red flags. Test and ski lower-angle slopes to assess stability before stepping into steeper avalanche-prone terrain. 

Let us know what you find out there by submitting an observation.

Ski and ride safe

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