Boletín de aludes

Olympics

Northwest Avalanche Center
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Peligro de aludes

Tue
Alta montaña
2 · Moderado
Límite del bosque
1 · Débil
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

In a recently wind-loaded location, you can still trigger a slab within stiffer surface snow. Note the most recent direction of wind transport depositing snow from the scoured side of ridges to the lee side.  Continue to steer around these pillow-like deposits on steep or unsupported slopes, particularly at upper elevations.

Problemas de aludes

  • Wind Slabs

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

    Most wind transport of snow occurred at least 36 hours ago by the time you enter the terrain on Monday.  E winds moved snow on Saturday, creating shallow slabs that have isolated reactivity on the most heavily loaded slopes near ridgelines at middle elevations; but slabs may be more prevalent at upper elevations. Shifting wind directions have formed cornices on a variety of aspects, so you should use the freshest, sharpest ones to point to the locations of the fresher, more reactive slabs.  Snow underneath these cornices may look fatter or smooth and lens-shaped. It may also be a bit firmer than the snow underneath it, so use small test slopes to sample these slabs before getting onto something more consequential.  In areas where you suspect recent deposits of 6" of snow may lurk, steer around steep or extreme terrain, particularly those where you lose sight of the fall line.

    Slope testers were hitting a variety of slopes at middle elevations without reports of releasing slabs on Saturday and Sunday, and entrainment of dry loose surface snow was minimal. However, keep in mind that we don't yet have reports from upper elevations where the winds likely transported more snow. With uncertainty higher at these upper elevations, it's a good idea to choose less consequential terrain.

    Example: Cornices and scoured slopes are great clues to help you anticipate possible wind-loaded slopes. 

    Photo: Sam Siemens-Luthy

Avalanche Discussion

Temperatures warmed 25-30F on both Saturday and Sunday following one of the coldest days in recent memory on Friday.  A time series in the gallery shows the cold week at Hurricane Ridge with the extraordinary drop in temperatures on Friday and the east winds that developed on Saturday. The warming on Sunday was enough to moisten snow surfaces directly impacted by the sun, initiating some rollerball activity on Sunday, but likely limiting the potential of wet loose activity somewhat moving forward. We expect ridgeline temperatures to rise to the freezing mark on Sunday, so expect more rollerballs and some small wet loose avalanches above the 3000-4000 ft inversion elevation. Most of these avalanches will be harmless, but it's a good idea to limit your exposure, particularly in higher consequence terrain. 

The cold temperatures have preserved exceptional riding conditions on most aspects. Check out an excellent observation from a S-facing slop just below the parking area at Hurricane Ridge, showing a right-side-up profile above the breakable 1/8 crust and no layers of concern in test results. The top 6" or so of snow (12" around 3000-4000 ft) fell Thursday evening and redistributed more deeply on the southern half of the compass with cold temperatures preserving the snow.  A storm cycle Monday-Wednesday added over 2 ft of snow at Hurricane Ridge. NPS rangers measured 32" of snow accumulation since Sunday (with 4" of settlement). This snow sits above the breakable crust formed during mild temperatures on 1/8. Slab reactivity or wet loose avalanches should be limited to the snow above the 1/8 crust.

In many cases, 3 ft of recent snow lies on bare ground so consider the early-season obstacles that lie under the low-density snow as you travel. While it now looks like full-on winter, rocks, bushes, holes, creeks, and logs could lurk just under the surface. A photo in the gallery shows bare ground covering south-facing terrain up to 5000 ft just 10 days ago.

NWAC may issue a gray "No Rating" for an elevation band when there is not enough snow to present an avalanche hazard.

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