Sawtooth & Western Smoky Mtns

Problèmes avalancheux

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Very Likely

  Taille

  1.5–2.5

  2-3+ feet of settled snow have fallen in this zone since Monday (2.5-3 inches of SWE). More is falling this morning. You will encounter a wide range of problems related to this new snow today:

  SLABS: Large slabs failing in the new snow are very likely. The size and sensitivity of these slabs will increase as you climb into wind-affected terrain. Thanks to the strength of the wind, you can expect to see wind slabs at all elevations, though they will be smaller on lower elevation slopes. If the snow you are moving through is anything but fluffy powder, you are traveling in wind affected terrain. Enough snow has fallen that sensitive slabs are lurking even in sheltered terrain. Triggered slides will run fast and far on the stiff surfaces underneath. 

  LOOSE SNOW: Small loose snow avalanches will be easy to trigger on all steep slopes. If the sun makes an appearance for long this afternoon you can expect to see many of these slides happening naturally on slopes receiving direct sun. They'll start small but may become large as they pick up speed and material and rocket downslope. 

  CORNICES: It has been a very windy week and there has been no shortage of snow available for the wind to blow around. Unstable cornices have grown quite large, and are struggling to hang on to their ridgeline homes, threatening the starting zones below. Be cautious when you are traveling on ridgelines, cornices will be easy to trigger and can behave in unpredictable ways. Large cornices can fail naturally at any point today. These beasts are very effective triggers for large slab avalanches as they tumble downslope.

  Avalanches involving the recent snow will be large enough to bury you. Natural and triggered slides involving the new snow can be very effective triggers for the weak layers described above. Any avalanche that breaks down into these layers will be large and destructive. 

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Very Likely

  Taille

  2–3

  Weak layers in the upper snowpack are being pushed to and past their breaking point by the ongoing storm. A smaller storm on Monday produced many avalanches that failed naturally and broke widely in this zone (see photo here). An additional 2 feet of snow have fallen here since and this uppermost weak layer responsible for Monday's avalanches is already buried underneath a 2-3+ foot thick slab.

  Avalanches that fail on persistent weak layers behave in ways that surprise even experienced users. These slides will break wide, wrapping around entire bowls and cirques. You can trigger these avalanches from long distances away from steeper slopes, including from flat terrain below large avalanche paths. Any of the storm snow avalanches described below can trigger these much larger slides. 

  ADDITIONAL DISCUSSION: Deeper weak layers exist in the snowpack. You'll find these layers buried underneath the very dense and very heavy slabs that formed from snow in the month of February. Smaller natural and human-triggered avalanches can step down to these weak layers, producing much larger avalanches. Slides that break on these layers can wipe out swaths of mature timber and will be unsurvivable.