Galena Summit & Eastern Mtns

Avalanche problems

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  2–2.5

  Slabs exist above widespread, weak layers (facets, surface hoar, crusts, and combinations). Persistent Slab avalanches are most likely in the thinner snowpacks of the Pioneer and Boulder Mtns in the southeastern part of this zone. Before triggering an avalanche, you're unlikely to experience obvious signs of instability like snowpack cracking and collapsing or whumpfing. Persistent Slabs can release in surprising ways and break much wider than expected. You are most likely to trigger a dense, 2-4 foot thick avalanche where:

  • The snowpack is less than 4 feet thick—relatively shallower spots may exist where the wind frequently blows, and the slab is not uniformly thick.
  • Any part of the slope you are on or connected to is steeper than about 35 degrees
  • The slope faces the northern 2/3 of the compass
  • A smaller wind slab or loose snow avalanche overloads the buried weak layers

  Additional Discussion - Wind Slabs: Recent snowfall and strong SW and W wind built slabs in areas exposed to the wind. On some slopes, slabs formed on crusts and/or weak snow, and avalanches could be easy to trigger or break wider than you expect. Slabs often form near ridgelines, along steep mid-slope gullies, or on aprons below steep cliffs. You can reduce your chances of triggering a wind slab by avoiding slopes with obvious signs of wind-loading, such as new cornice growth and large dunes or pillows of wind-blown snow.

  

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1–2

  Anticipate loose snow avalanches on very steep, rocky slopes receiving direct sun. Avalanche activity will follow the sun, beginning on SE-facing slopes, shifting to S-facing slopes midday, and more W-facing terrain this afternoon. These slides often initiate near the base of trees and rocks, gathering snow and growing in size as they move downhill. Rollerballs, or pinwheels, signify that the snow is heating up, and wet avalanches may soon follow. 

  While most will start small, they will be plenty large enough to knock you off your feet and carry you into unwanted terrain. Some slides have the potential to flank out into wider wet slab avalanches. Even small slides are consequential above terrain traps such as gullies, creeks, and thick timber. Plan your day to avoid lingering under steep, sunny slopes.