Continental

Lawinenprobleme

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  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Likely

  Größe

  2–3

  Strong north winds began yesterday with gusts in the upper 50s measured at Thompson Pass.  Similar conditions will continue today, with wind strength potentially peaking this afternoon.

  North wind will continue to promote dangerous avalanche conditions as wind redistribution creates stiffer slabs atop an already upside down storm slab.  Human-triggered avalanches are likely up to 5 feet in depth.  Wind slab depth will vary depending upon location, but drifts up to 5 feet in depth can be expected.  Even shallower wind slabs once triggered will have the potential to step down to the new/old interface or instabilities within the new snow.  

  Pay attention to wind direction and avoid areas that are being actively loaded.  Hard snow over soft will indicate wind loaded snow and shooting cracks are a bullseye indicator of instability.  Dangerous wind chill is expected today with -50° values forecasted for Thompson Pass.

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  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  1.5–2.5

  Instabilities still exist in areas that are protected from north wind today.  The 1/28 snowstorm delivered 3+ feet of new snow from the coast to 46 mile with rising temperatures at the end of the storm and strong wind blowing from multiple directions.  This new snow fell on a variety of wind damaged surfaces.  

  New snow from last week has been observed as being slabby at the surface even in areas protected from outflow winds.  Instabilities have been observed and reported in the new snow as recently as 1/31.  Data collection has remained limited as deep upside down storm slabs have created very difficult travel conditions making travel into the upper elevations very challenging.  Not many slopes have been tested so far, so sensitivity within new snow is unclear. Although recent stability tests and poor structure indicate that human triggered avalanches are certainly possible even in areas where surface snow is unaffected by current outflow winds.

  Hand shear tests are nearly impossible to perform due to the depth of new snow.  Be careful using test slopes as failure on even small slopes could be dangerous due to the mass involved.  Extended column tests and propagation saw tests are probably the best way to assess upper snowpack stability.  However, these can be difficult to perform properly and may provide false stable results.

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  Glide Cracks

  • Alle Höhenlagen

  Wahrscheinlichkeit

  Unlikely

  Größe

  2.5–3

  The sensitivity of Glide avalanches is not possible to predict.  These release independent of snowpack stability and are tied more to a complicated relationship between the underside of the snowpack and the friction at the ground.  This interaction is not well understood.  What is well understood is that this avalanche problem produces deadly avalanches that include the entire snowpack and can release spontaneously.

  Travel advice is very simple: avoid spending time under glide cracks.  Glide cracks are generally easy to identify as they look like crevasses, but exist in non glaciated terrain.  New snow and wind will make identifying these more difficult, as they may have been covered.