Galena Summit & Eastern Mtns

Problèmes avalancheux

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Likely

  Taille

  2–3

  Skiers and riders have remotely triggered several 2-4' thick persistent slab avalanches in recent days (view Observations and Avalanches). Sun Valley Heli Ski staff observed an extensive natural avalanche cycle in the Pioneer Mtns south of the East Fork of the Big Wood River. The natural and human-triggered slides appeared to fail on persistent weak layers (crusts, crusts and facets, or facets) in the middle or bottom of the snowpack. The recent activity has been focused on slopes commonly exposed to the wind. While the slides occurred predominantly on E-NE-N aspects, triggering avalanches is possible on all aspects.

  Persistent Slab avalanches can release in surprising ways. You can trigger them from flat or low-angle terrain long distances away from steep slopes, and they can break far above you. Several riders or skiers could safely ride a slope before someone triggers a slide. They can break hundreds or thousands of feet wide. Before triggering an avalanche, you may not experience snowpack collapsing or other obvious signs of instability. 

  Unfortunately, snowpack stability tests will not conclusively determine if a given slope will or will not produce a Persistent Slab avalanche. If your primary goal is to not get caught in an avalanche, staying off of and out from below steep slopes is the most reliable way to reduce your risk.

  Observations indicate these avalanches are most likely in the southern part of this zone. 

  

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Likely

  Taille

  1–2

  You could trigger soft wind slabs up to 3 feet thick in exposed terrain. Yesterday's heavy snowfall and wind formed slabs, drifts, and cornices near upper elevation ridgelines and in some middle elevation terrain. Today's wind may continue building slabs and wind features. 

  Cornices, drifts, dunes, rippled snow surfaces, and chalky snow pillows are visible clues that the wind has been at work. If you see cracks shooting out in front of your skis or boards, you've probably found a wind slab. If you feel the snow stiffen beneath your sled or skis, its time to steer clear of large or consequential avalanche paths.

  Cornices have grown substantially this week, and the most recent growth may be very soft. Natural or human-triggered cornice fall can trigger wind slabs beneath cornices. Give large or overhanging cornices a wide berth. 

  In wind-sheltered terrain, today's sunshine may consolidate and stiffen the fluffy powder near the surface. This process raises the possibility of natural or triggered avalanches involving yesterday's snowfall on very steep slopes. Conditions can change rapidly on sun-drenched avalanche paths. 

• 

  Loose Dry

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Very Likely

  Taille

  1–2

  You are very likely to trigger sluffs in steep terrain, and some of these could be big enough to knock you over or bury you. The chance of natural loose snow avalanches will rise as direct sunlight shines on steep slopes. The increased threat will follow the sun around the compass, beginning on E-SE aspects in the morning, moving to S-facing slopes by noon, and finishing on SW-W aspects in the afternoon. 

  Many of these slides will be small and relatively harmless; however, large slopes, chutes, and couloirs could produce big, powerful sluffs that could easily catch, injure, or bury people. Be aware of the terrain above you and where an avalanche could carry you. Don't underestimate the potential size of the sluffs.