Blues

Lawinenprobleme

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  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  1–2

  The last week of warm and sunny weather has melted snow in the upper snowpack and water has dripped through the snow until it has reached a crust buried in the upper 2 feet of the snowpack.  This has created unstable upper snowpack conditions during the heat of the day.   Many natural wet loose avalanches have been observed since last weekend.  These often occur on solar aspects near rocks or cliff bands.  Last night, temperatures dropped below freezing at some, but not all weather stations.  Until we see a solid freeze at night coupled with lowering daytime temperatures, the likelihood of triggering wet loose avalanches in terrain steeper than 35 degrees remains possible.  

  Cloudy skies can help slow the onset of natural wet loose avalanches as the amount of direct sun that warms the surface of the snow is reduced.  That being said, the upper snowpack has been affected by strong solar input and multiple days without freezing temperatures and will take some time to lock back up once temperatures start to drop.   Even a smaller wet loose avalanche has the potential to knock you off your feet and carry you over consequential terrain or push enough snow into a terrain trap to bury you.  

  In your travels in the mountains today, pay attention to how wet the snow is under your feet or machine.  Get curious and dig down a few feet and see how wet the surface snow is as well as how deep water has percolated in the snowpack.  If you step off your machine or boards and are sinking up to your boot tops in wet snow, it's time to head to terrain less than 30 degrees in steepness.  

  

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  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Unlikely

  Größe

  1–2

  As your search for soft snow leads you to shadier aspects, you need to have your wits about you. 

  Last week forecaster Michael Hatch traveled to Spout Springs and found a thin layer of buried surface hoar down 8" at the new/old snow interface on a north-facing slope near 5200' in elevation. Surface hoar is notorious for being a persistent and reactive weak layer when buried.  If you collapse this weak layer in a shallower area on the slope (say around rocky terrain or wind-scoured areas) or roll over a steep convexity, the propagating fracture could trigger a large and destructive avalanche.  Avoid potential trigger points and steep (>35 degrees) convex rollovers, especially near treeline and mid-slope. Surface hoar forms in more open and protected terrain with little sun, so you'll find in mostly on shady slopes NW-N-NE. There is a lot of spatial variability of this layer across the slope. It is hard to see in the snowpack as it is a very thin layer. When in doubt, do snowpack tests, and better yet, choose lower-angle terrain to recreate in. You can always choose to avoid avalanche terrain altogether, and at the very least, ride on aspects where this problem is less likely to exist. 

  To decrease your chances of getting mixed up in this sort of fight, a thorough snowpack analysis is suggested before committing to any slope greater than 30 degrees on Northeast through Northwest aspects near and above treeline.  When you have uncertainty around the presence of these persistent weak layers, choose simple terrain less than 30 degrees.