West Slopes Central

Lawinenprobleme

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  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Likely

  Größe

  1–2

  Intermittent pulses of new snow and moderate winds have loaded alpine start zones over the last several days. Westerly winds reach into the 30’s Friday night, before backing off and swinging north Saturday morning. Expect to find newly formed slabs, drifts and pillows below ridgelines, along gully walls, and on the backside of outcrops and steep roll-overs.  

  These slabs will probably stay reactive to human triggers throughout the day, with depths ranging from shallow to a couple of feet deep. Give them some respect, especially on shady upper elevation slopes where you are likely to find weak layers buried in late January (see the next avalanche problem). 

  

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  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Likely

  Größe

  1.5–2.5

  Our January dry spell created a facet-crust-facet (weak-strong-weak) structure that is now around two feet deep.  We have not seen many avalanches on it, but we do have reports of two remotely triggered slides at the beginning of the recent storm cycle. This structure is most prevalent in shady alpine areas and is easy to find where it exists (see pic and look for an obvious crust a couple of feet deep).  

  Although observations suggest that the facets are rounding and gaining strength, the structure is still present, and we are approaching 4 inches of SWE in the storm cycle ... which suggests triggering an avalanche on it remains a possibility. 

  There are a couple problems with a scenario like this: 1) You are most likely to trigger an avalanche in this layer by triggering a smaller windslab that loads the slope, and 2) If you do trigger it it will create a relatively big and dangerous slide, and 3) The layer may not be uniform across the landscape – which means that one steep slope may be stable, while the next is not. 

  Whumphs, collapses, and/or deeper shooting cracks are good indicators of this type of instability. Avoid large, unsupported slopes and steep roll-overs in shaded alpine terrain.