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

  1.5–3

  The Persistent Slab problem is unusual in how many recent avalanches we've seen in middle elevation terrain (view Observations). In areas sheltered from the wind, expect to find 1-2.5 foot thick slabs. In terrain affected by the wind, you'll find much denser, 2-5 foot thick slabs. The avalanches are failing on a variety of weak layers: surface hoar, facets, and crust+facet combinations. Large natural and human-triggered avalanches have been observed on most aspects. Assume this problem exists on all upper and middle elevation slopes and on shadier, lower elevation aspects.

  The avalanches described above could "step down" to weak snow near the ground, producing much larger, unsurvivable avalanches. At least 2 avalanches did so this week in the Banner Summit zone (watch video). This layer of weak snow near the ground exists in upper elevation terrain and on most shaded middle-elevation slopes (W-N-E). 

  Some facts to help you travel safely today:

  • You can trigger avalanches remotely—from flat or gentle terrain below, above, or to the sides of steep slopes.
  • Avalanches can break well above you, either while you are descending or at the bottom of a slope.
  • Avalanches are pulling back into relatively flat terrain above steeper slopes.
  • Some recent avalanches were hundreds to thousands of feet wide.

  

• 

  Loose Dry

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Possible

  Taille

  1–1.5

  Smaller avalanches involving only the snowfall since the last big storm could release naturally (on their own) and trigger the dangerous Persistent Slabs described above. These avalanches should not be large enough to bury people unless you are above terrain traps (creeks, roadcuts, etc). You could see several types of smaller slides today:

  • Dry or wet loose snow avalanches: This morning's sunshine could be enough to trigger sluffs. These are most likely at middle and upper elevations, on very steep slopes that directly face the sun. Small cornice fall or a little wind-blown snow can also trigger these slides. These will be most common in the western mountains that have seen more snowfall and less wind in recent days.
  • Wind slab avalanches: If you're traveling in exposed upper elevation terrain, you may find and trigger small pockets of wind-blown snow.

  The photo shows a natural avalanche that appeared to be triggered by a tiny wet avalanche or rollerballs coming from above, indicating how easy it is to trigger Persistent Slab avalanches. Pay attention to what's above you as you're traveling.