Sawtooth & Western Smoky Mtns

Lawinenprobleme

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  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  1–2

  Expect to find fresh wind slabs in the alpine. Yesterday a professional observed the crown of a slab avalanche in wind-affected, upper elevation terrain of the central Sawtooths. Cracking was reported in 1' thick wind drifts south of Smiley Ck (photo). Observers noted strong wind in the alpine, lifting low-density snow into plumes that extended for hundreds of feet into the air. Wind speeds will ease this morning, but ramp up again to build additional small slabs this afternoon and evening.

  Wind slabs often form near or just below ridgelines, on the sides of cross-loaded chutes, or on aprons below steep cliffs. Many of them rest on slick crusts. This means they may be easy to trigger, break wider than expected, and will pick up speed quickly as they travel downslope. 

  Pay attention to how the snow feels under your skis or boards. If the snow surface suddenly stiffens or becomes more supportable, you've found a wind slab. Cracks shooting out in front of your skis or boards are a red flag warning you to be cautious. Surface clues like dunes or ripples can tell you the wind has been at work.  

  ADDITIONAL DISCUSSIONWeak layers consisting of crusts, facets, and surface hoar, exist in the upper part of the snowpack. The weakest snow we've seen is on the shady half of the compass, spanning upper and middle elevation terrain (photo). This persistent slab occurred last week after a small storm near Galena Summit (photos and details here). Better visibility today will allow us to see whether Tuesday's snow and recent wind were enough to produce similar slides. Choose more conservative terrain on shadier slopes as you climb in elevation, particularly where the wind has stiffened the snow surface or formed drifts.

  

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  Loose Dry

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Certain

  Größe

  1–1.5

  The sun will initiate loose snow avalanches on very steep slopes. Avalanche activity will start on E-facing slopes this morning, follow the sun as it moves through the southern sky, and end on W-facing slopes in the afternoon. These slides commonly initiate near warm rocks, fanning out and collecting snow as they go. Human triggered loose snow avalanches (or sluffs) are also possible on very steep, shadier slopes that are sheltered from the wind.

  Although likely to be small, sun-induced avalanches will be numerous and can travel quickly on the slick surfaces beneath them. Pay attention to the terrain above you. Large slopes can produce slides big enough to knock you off of your feet and carry you places you don't want to go.