Salt River and Wyoming Ranges

Problemas de aludes

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta montaña
  • Límite del bosque
  • Bajo el límite del bosque

  Probabilidad

  Possible

  Tamaño

  1.5–2.5

  We are in the midst of the first major warm-up of the season, and the wise move is to stand back and watch the show instead of trying to outsmart exactly where the persistent layers are most likely to fail. You're more likely to trigger persistent slab avalanches in areas where the wind has stiffened the snow surface or formed drifts, but they are possible in sheltered terrain as well. Activity in the past seven days indicates that though persistent problems will trend more and more unlikely with more warm-up and overnight refreeze, we are not out of the woods yet. March 20 and March 29 exist 1-3 feet in depth, and remain in the top meter of the snowpack. Currently, I'm avoiding terrain where both of these layers exist out of uncertainty, particularly where they exist as a crust/facet combination, while slopes are seeing direct solar input and while water is moving in the snowpack in the heat of the day. Deeper weak layers formed earlier in the season composed of crusts, facets, and depth hoar remain a concern of highlight in the Wyoming Range. Triggering wet snow movement or a wind slab here could step down to these layers resulting in a large to very large avalanche.

  ADDITIONAL DISCUSSION

  It is worth noting here that as we venture into terrain above 9,000 feet, a slightly different snowpack exists. Upper-elevation terrain was still seeing some dry snow transport up until yesterday, and even small wind slabs in the consequential terrain can prove incredibly hazardous. Yesterday in the Greys Zone, I found small pockets of stubborn 6-8 inch slab that will remain more sensitive today. Regardless of the terrain you enter today, the snowpack is reaching a peak throe of transition over the next 48 hours. It is also worth noting that as we progress more days into the freeze-thaw cycle so late in the spring, we may also see icy conditions set up on SW-S-SE aspects in the alpine quicker than we expect.  

   

  

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta montaña
  • Límite del bosque
  • Bajo el límite del bosque

  Probabilidad

  Likely

  Tamaño

  1–2

  Yesterday I observed a handful of wet loose avalanches in the Snake River Canyon. For the most part, these avalanches involved thin layers of wet snow near the surface. With intense sunshine and even warmer temperatures today and tomorrow, I expect wet avalanche activity to continue. The size and destructive potential of these slides may increase as meltwater pushes even deeper into the snowpack. In favorable terrain (long, steep, and rocky slopes) these avalanches may become large enough to bury you today. I will be avoiding avalanche terrain later this afternoon as things trend more unstable.

  This problem is most likely:

  1. On steep upper-elevation slopes that directly face the sun
  2. On slopes sheltered from the wind 
  3. On lower and middle elevation slopes that still have a foot or more of snow, regardless of the direction they face.

  The snowpack was able to weakly freeze last night, but it won't take long for the surficial crust on top to break down. You'll be most likely to encounter natural and human-triggered wet loose avalanches on steep slopes receiving direct sunshine. Avalanches will also become problematic on steep, shaded slopes at lower and middle elevations as the day heats up.  As more snow is warmed, more material is available to move downslope.