Galena Summit & Eastern Mtns

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1–2

  What and where is it?  You may be able to trigger 1-3 foot thick slabs on wind-loaded slopes near and above about 9000'. The threat of triggering large slides is highest in alpine terrain. Some slabs overlie crusts and/or thin layers of weak, faceted snow; the slabs could break wider than expected. Triggering these large avalanches is most likely on "prime time" slopes angles for slab avalanches—slopes approaching or exceeding about 40 degrees. 

  How can we recognize and manage this problem? The wind slabs are fairly easy to spot and avoid. Watch for smooth pillows below ridgelines and cornices as well as on the sides of cross-loaded gullies and on the aprons of large chutes and couloirs. Dunes and ripples on the surface are clues the wind has been at work transporting snow, and cornices falling are great triggers for the wind slabs below them. If you feel the snow surface getting stiffer, it's time to pay attention. Cracks shooting out from your skis or sled are an obvious sign that you've found a wind slab. Hard wind slabs sound hollow, like a drum, and behave unpredictably; they can break above you and wider than expected. 

  Additional Discussion: While unlikely, we can't completely write off triggering very large avalanches on middle and upper elevation slopes facing away from the afternoon sun. These avalanches would fail on a layer of weak facets near the ground. Unfortunately, you probably won't receive any obvious signs of instability before triggering one of these lingering monsters. Triggering a slide on this layer is most likely in rocky, heavily wind-affected areas where the snowpack depth is variable.

  

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1–2

  What and where is it? The chance of relatively small, natural and human-triggered wet loose avalanches will increase on slopes that check most or all of the following boxes:

  • Receiving direct, unobstructed sunshine.
  • Sheltered from the wind.
  • Very steep (approaching or over about 40 degrees).
  • Near exposed rocks.

  How can we recognize and manage this problem? The threat of wet loose avalanches generally follows the sun around the compass: SE-S aspects in the morning, S-SW facing slopes mear mid-day, and SW-W aspects in the afternoon. Watch for rollerballs and pinwheels, signs the surface snow is becoming moist and wet loose avalanches may follow. These slides often initiate near the base of trees and rocks, gathering snow and growing in size as they move downhill. While generally small, these slides could knock you off your feet or push you where you don't want to go.