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 and could break wider than expected. Triggering these large avalanches is most likely in "prime time" avalanche terrain: slopes approaching or exceeding about 40 degrees in steepness. 

  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. Slabs also formed on the aprons of some large chutes and couloirs. Dunes and ripples on the surface are clues the wind has been at work transporting snow.

  Falling cornices can be great triggers for the wind slabs below them. Hard wind slabs sound hollow, like a drum, and behave unpredictably; they can break above you and wider than expected. You may or may not experience snowpack cracking or collapsing—clear signs of unstable conditions—before triggering a wind slab avalanche. 

  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

  Unlikely

  Size

  1–2

  What and where is it? Today's expected cloud cover should keep wet avalanche activity at bay. However, any extended periods of unobscured sunshine and light wind will bring these slides into play. 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 over or push you where you don't want to go.