Boletín de aludes

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Peligro de aludes

Sat
Alta montaña
2 · Moderado
Límite del bosque
1 · Débil
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 5 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

You could trigger avalanches where yesterday's storm built sensitive drifts. Look for this problem near exposed ridgelines and along the sides of steep gullies. Loose snow avalanches are very likely, particularly during the heat of the day on very steep, sun-drenched slopes. 

Problemas de aludes

  • Wind Slabs

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

    Yesterday, observers reported small, sensitive drifts near the entrance to steep lines in the southern Sawtooths. In the Boulders, Ben and I both found signs that the new snow was reluctant to bond to the underlying snow surface. 

    North wind is forecast to increase in speed today. This bump may only affect the uppermost elevations, but up to 12" of recent light, dry snow at the surface will be easily drifted. Look for pillowed or drifted areas on the lee sides of ridges (photo above/right), gullies, and other prominent terrain features. In steeper alpine terrain, wind slabs may form along the sides of couloirs and on aprons below cliffs.

    This small wind slab released on a wind-loaded upper elevation ridge in the Boulder Mountains near Senate Pk. SW-aspect near 10,100'. Photo: J. Preuss

  • Loose Wet

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

    The sun will return today stripping new snow from sunny slopes during the heat of the day. This problem will roughly follow the sun through the southern sky, starting in the E, moving to the S midday, and eventually to the W by the afternoon. Thankfully this problem is predictable and can be avoided by staying off of and out from under very steep, rocky sun-drenched slopes.

    ADDITIONAL DISCUSSION:Dry loose avalanches are a concern on cooler, shadier slopes. Recent snowfall will "sluff" in very steep terrain not affected by the wind. This minor hazard can be amplified on consistently steep, larger slopes or confined terrain like chutes, where sluffs are harder to escape.

Avalanche Discussion

In this zone, it appears that snowfall is heavily localized to the southern Smokys near Dollarhide and out toward Baldy. You're much more likely to run into well-defined avalanche concerns of any kind in these areas with up to a foot of new snow than in the surrounding areas where snow totals are 6" or less.

Let's assume you started your day early and plan to climb and ski off a peak in this zone, what might you expect to see? 

Since you started early, the snow will be dry, modest low elevation snow accumulations will make travel easy as you close the gap to your peak of choice. As you gain elevation, you'll notice the snow depth increase. No worries, you're in lower angle, safe terrain and the snow surface is neither drifted nor wet from the sun. 

As you start to top out temperatures drop, wind speeds increase, and you find the snow surface is becoming stiffer. You make a mental note of these drifts and continue up the ridge. Now almost noon you start to see roller balls and small sun-induced loose snow avalanches in very steep terrain. It looks like the sun is having an effect earlier than you expected. Maybe we're too late for that steeper SW-facing run at the head of the basin. Good thing we have a plan B. 

Shifting course to more shaded terrain you arrive atop your line. This protected portion of the drainage hasn't seen as much wind as the exposed ridge you observed earlier. It is steep though, and there's ample new, light dry snow. This has you thinking of how to manage the dry loose (sluffs) you're likely to encounter. A clean runout and several turns later you're high-fiving in the basin below. Nice work! 

This hypothetical scenario sounds like a great day in the mountains and hopefully helps illustrate some of the problems you should be thinking about along the way. Slab avalanches in areas exposed to the wind and loose snow avalanches, both naturally occurring due to sun and dry loose sluffing, all deserve respect. 

Today, flexibility is the key to success. Give yourself some options. Be prepared to turn back, or pick simpler terrain. As always, if something doesn't feel right, don't be afraid to back off and return another day. Enjoy this last bit of "wintery" weather, it's looking like spring will officially arrive in the mountains next week. 

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