Galena Summit & Eastern Mtns

Problemas de aludes

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta montaña
  • Límite del bosque
  • Bajo el límite del bosque

  Probabilidad

  Likely

  Tamaño

  2–3

  What is it?  Look at the photo to the right/below; we added up to 2 feet of snow since snowmobilers triggered that avalanche from a quarter mile away.Dense, 3-5 foot thick slabs overlie persistent weak layers (sugary facets, surface hoar, and/or crusts) on most aspects and elevations. Wind-loaded slopes are the most dangerous, but the ongoing storm makes slopes sheltered from the wind suspect, too. Yesterday, professionals traveling in the northern Sawtooth Mtns reported some snowpack cracking and questionable stability at the storm snow interface. The snowpack needs a break to adjust to yesterday's big storm, but it's not getting it today. Instead, expected snowfall and wind will continue stressing buried weak layers.

  Where is it?  This problem is widespread through all elevations and most aspects. While the vast majority of December's avalanche activity occurred on W-N-E aspects where the weak layers are ugliest, sunnier SW-S-SE facing slopes are not guaranteed to be safe. Wind-loaded slopes are far more dangerous than sheltered terrain. 

  How can you recognize it?  This persistent slab problem is widespread; assume it exists on all slopes until proven otherwise. You may or may not experience snowpack collapsing and/or cracking while traveling. These red flags are obvious signs of instability. Wind-loaded areas feel stiffer under your skis or sled and keep you from easily sinking into the snowpack.         

  How can you manage it?  Avoiding slopes steep enough to slide is the only reliable way to manage this problem. Persistent slab avalanches are tricky. If you're playing near steep slopes, you could trigger slides remotely (from gentler terrain above, below, and to the sides of steep slopes—explanatory video here). These avalanches may break wider, deeper, and higher on the slope than expected. 

  

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta montaña
  • Límite del bosque
  • Bajo el límite del bosque

  Probabilidad

  Very Likely

  Tamaño

  1.5–2.5

  What is it?  Yesterday's rowdy storm formed soft and hard wind slabs in exposed terrain. In the afternoon, Ethan observed fresh wind slabs up to 2 feet thick near Titus Ridge.Today's snowfall and wind will continue building slabs, and natural avalanches are possible. The wind slabs lie above a variable surface (facets, crusts, "regular" snow, wind-polished surfaces, etc); some slabs will be easy to trigger while others may be "stubborn" or hard to trigger. Wind slab avalanches could "step down", triggering the large persistent slab avalanches described in Problem 1. 

  Where is it?  Strong and extreme winds can form slabs in unusual and unpredictable locations as well as typical places near ridgelines. You may find them near or far below ridgelines, on the sides of gullies, and near prominent terrain features in normally sheltered areas.

  How can you recognize it?  Cracks shooting out from your skis or sled are an obvious sign of instability. Watch for drifts, dunes, and ripples on the snow surface. Wind slabs can have a smooth, chalky appearance and feel and sound hollow, like a drum. The lower-density snow that fell overnight and is continuing today may hide or disguise large wind slabs that formed yesterday. Wind-deposited snow will be stiffer and keep your skis or snowmobile closer to the surface.       

  How can you manage it?  Given the high likelihood of triggering wind slabs today, the simple answer is to avoid wind-loaded avalanche terrain. Hard slabs are notoriously unpredictable; these avalanches may break wider than expected or higher on the slope above you.