Bulletin d’avalanche

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Sawtooth Avalanche Center
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Danger d’avalanche

Sat
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 5 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

You could trigger small avalanches at upper elevations where new snow and wind create sensitive drifts. Wet avalanches are possible on any steep slope where rain is falling or where you find yourself sinking deep into a soggy snowpack.

Problèmes avalancheux

  • Wind Slabs

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

    Wind speeds will remain elevated this morning from the S and SW accompanied by 3-5" of new snow. Expect to find small, sensitive wind slabs in terrain exposed to the wind—particularly at upper elevations. These slabs should be fairly easy to identify and avoid. Look for them near and just below exposed ridgelines and prominent terrain features. Cracks shooting from your skis or sled are a sure sign that you've found a sensitive slab.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Yesterday was the hottest day of the week. Increasing clouds last night prevented a solid freeze as many middle and low elevation areas hovered near or slightly above freezing. Adding insult to injury, rain is expected this morning below about 6,800'. 

    Wet snow and rain will add additional water to an already soggy snowpack at low elevations. An early start won't help you today and even some shadier slopes are suspect as rain weakens snow that's remained relatively dry.  To avoid this problem, stick to cooler, dry snow well above the rain line.

    ADDITIONAL DISCUSSION:The most prominent weak layers in this zone are depth hoar near the ground (buried 4-6' deep) and crusts associated with facets in the middle of the snowpack (buried 2-3' deep). Meltwater seeping into the snowpack adds a layer of uncertainty to the slab avalanche equation. A large, destructive wet slab avalanche occurred in the Sawtooths at the beginning of March (photo here, details here). Steering clear of areas with gloppy, unsupportable snowpacks—including areas below large avalanche paths with mushy snow conditions—is a simple way to minimize the chances of triggering or tangling with large slab avalanches. 

    (3/13/2021) Recent-looking wet slide reported in the Sawtooths. This slide may have released as a wet slab. Photo: T. Harrison

Avalanche Discussion

It's going to be a stormy, mild day today. If you're headed to upper elevations you'll need to keep an eye out for thin, freshly formed wind slabs. Near and below the rain line wet avalanches remain the primary concern.

Wet Avalanches:At elevations below about 7,000', we have a couple of factors working against stability and enjoyable riding conditions. The first obviously being rain, and the second is an already mushy snowpack that didn't get the benefit of a solid overnight freeze. Wet avalanche concerns are driven by meltwater in the snowpack. Wet loose avalanches are simply wet, cohesionless snow sluffing off steep slopes. Wet slab avalanches occur when the meltwater weakens the bond between a slab and the surface below. The persistent weak layers in the middle and near the base of our snowpack are good candidates to produce these types of slides. The combination of prolonged near and above freezing temperatures and rain will keep these wet avalanche concerns on the table. Fortunately, you can avoid these problems by finding cooler, dry snow to enjoy. 

Wind Slabs:At upper elevations, moderate to strong wind and new snow will build a fresh round of thin wind slabs. While I don't expect these slabs to be large, they may be sensitive, particularly where they rest atop small facets on more shaded upper elevation slopes. Fresh slabs may guard the entrance to some steeper lines in the alpine where the consequences of getting knocked off your feet are elevated. 

Being adaptable is the name of the game today. Spring-like storms are less predictable than winter storms, largely due to enhanced convection and temperatures near freezing. They can produce heavy, localized precipitation (both rain and snow) leading to rapidly changing conditions. Be flexible and be prepared to switch to plan B. Much of the uncertainty associated with today's storm will diminish as temperatures and snowfall decrease into the weekend. 

Régions couvertes