Galena Summit & Eastern Mtns

Problèmes avalancheux

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Possible

  Taille

  1–2

  Recent northerly winds have formed both soft and stiff slabs. Some of these slabs overlie weak facets or crusts—especially on SE-S-SW aspects—and may be more sensitive to triggering than you might expect. Yesterday in the southern Sawtooths near McDonald Pk, I observed a wind slab that stepped down to one of these deeper weak layers (report). 

  Wind slabs will be thicker, wider, and more common at upper elevations near Galena Summit. Look for wind-blown snow immediately below exposed ridgelines, on the sides of gullies or chutes, and near large terrain features.

  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. Wind-deposited snow will be stiffer and keep your skis or snowmobile on or closer to the surface. Managing this problem is relatively simple. Steer clear of recent wind drifts and slabs on slopes steeper than about 35 degrees. 

  

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Unlikely

  Taille

  1.5–2.5

  Triggering a large persistent slab avalanche on weak, sugary facets buried deeper in the snowpack would take some bad luck. The video to the right/above describes this problem. You are most likely to find this scenario on slopes with all or most of the following characteristics:

  • Wind-swept alpine terrain, especially in the Pioneer, Boulder, and White Cloud Mountains
  • Steeper than about 35 degrees
  • Variable snowpack depths with areas less than 2 feet deep and/or rocks poking through the snow surface
  • Large, hard wind features somewhere on the slope

   Don't expect obvious signs of instability (snowpack collapsing or cracking) before a large avalanche releases. Snowpack stability tests are of little use in situations like this. The only way to effectively reduce the odds that you trigger one of these slides is to avoid terrain that checks all or most of the "boxes" above.