Galena Summit & Eastern Mtns

Problèmes avalancheux

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Very Likely

  Taille

  1–2

  Natural and human-triggered wet loose avalanches are likely on steep, wind-sheltered slopes directly facing the sun.

  • These slides often initiate near the base of trees, rocks, and cliffs, starting as small point releases and entraining snow and fanning out as they move downhill. These slides could trigger larger slab avalanches (example) as they move downhill.
  • The majority of these slides will involve only the recent snowfall, but they can grow large enough to knock you off your feet or sled and carry you where you don't want to go. Even small slides are surprisingly difficult to escape and are consequential above terrain traps such as gullies, creeks, and trees.
  • Rollerballs (video), pinwheels, and wet, slushy snow surfaces are clear signs the snow is heating up; wet avalanches may follow. Avoid lingering under big avalanche paths and steep, rocky slopes while they directly face the sun.

  Additional Discussion - Cornices: Cornices could break on their own as they sag during the heat of the day. Natural cornice fall can trigger both wet loose slides and the larger slab avalanches described below.

  

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Possible

  Taille

  1.5–2

  It remains possible to trigger a 1-3 ft thick persistent slab avalanche on buried weak layers (sugary facets, surface hoar, and crust + facet combinations).

  • This problem is worst on recently wind-loaded, middle and upper elevation slopes facing NW-N-NE-E. However, today's intense sunshine and heat also make recently wind-loaded avalanche paths facing the southern half of the compass suspect.  
  • Avoiding avalanche terrain is the only surefire way to manage this problem. Short of that, you can reduce your risk by avoiding large, obviously wind-loaded avalanche paths and those with ugly consequences if you are caught in a slide.
  • Look for smooth snow pillows, dunes, textured snow surfaces, and cornices. Feel for stiff snow and listen for hollow or "drummy" sounds. Wind-affected snow is stiffer than the powder found in sheltered locations.
  • Snowpack cracking and collapsing are clear signs of unstable conditions. However, don't expect to experience obvious signs of instability; the first clue may be the avalanche you trigger. Avalanches could break above you and wider than expected. 

  Additional Discussion - Wind Slabs: Over the weekend, observers reported fresh natural avalanches in wind-loaded terrain in the White Cloud Mtns, and several large avalanches released naturally in the western Smoky Mtns. The last storm formed wind slabs below corniced and exposed ridgelines, on the sides of cross-loaded gullies, and in cirques below steep faces, large cliff bands, and chutes. The slabs are largest and most widespread at middle and upper elevations. You could find wind slabs both at ridgelines and lower on slopes than you might expect (see photo to right/below). Give cornices a wide berth; they can break on their own or with the weight of you or your sled. Falling cornices are great triggers for slab avalanches.