Continental

Lawinenprobleme

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  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Likely

  Größe

  1–2.5

  Strong north winds began overnight with gusts to 58 mph recorded.  Winds are initially blowing out of the NW and will likely move to NE during the day and intensify with gusts to 90 mph possible during the day.  These strong winds will be aggressively transporting snow and gouging into the snowpack, creating windslabs on lee aspects 1-2+ feet in depth.  Wind slabs are the most sensitive when they form, human triggered avalanches will be likely today.

  The strength of north wind that we are expecting will be stripping most areas.  Expect to find wind slab deposits on the lee side of catching terrain features such as cross loaded gullies.  At upper elevations, wind slabs that form on the lee side of ridges may exist further down from ridgelines than what is typical.   New slabs will turn stiff fairly quickly during the day tomorrow due to the strength of wind.  Wind slabs will likely have a hollow drum like feel and may have a rippled and/or pillowed look to them on the surface.

  Facets exist 8-18 inches beneath the surface that will increase the potential for large natural and human triggered avalanches today.

  Avoid slopes steeper than 30° that are being actively loaded by wind.

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  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Unlikely

  Größe

  1–2

  Faceted snow exists near the surface in all three forecast zones that was created by the mostly dry weather since 12/25.   These facets have been found to be rounding to some extent and mixed with other grain types, although remain a concern.  The distribution of this layer is not widespread due to previous north wind on 1/9 that removed it from windward slopes in wind exposed terrain.  It is very possible that the strong winds that are forecasted today will remove/blow away this weak layer in more places.  

  In multiple locations, this weak layer exists underneath wind slabs formed by the moderate 1/9 outflow event.  The major question moving forward will be:  Is the wind slab above these facets strong enough to withstand the damage that is going to occur with strong winds and leave faceted snow preserved?

  The presence of a potential persistent weak layer near the surface will become increasingly spatially variable (differnt from place to place).  Protected areas will be the most suspect.  Although, with the strength of wind forecasted these may be hard to find in close proximity to the road corridor.

  The presence of this layer will increase the odds and potential propagation length of human triggered and natural avalanches today.

  

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  Glide Cracks

  • Alle Höhenlagen

  Wahrscheinlichkeit

  Unlikely

  Größe

  2.5–3

   Glide avalanches are a strange beast that act differntly than other avalanche problems.  Full depth failure can occur independent of snowpack stability.  Or in other words, they can release even when a stable snowpack is in place.

  Since it is not possible to time their sensitivity the only way to mitigate this hazard is by avoidance.  First identify where glide cracks exist and avoid spending time beneath them.  Glide cracks are easy to identify.  They look like crevasses, but exist in non glaciated terrain.

  These do not produce small avalanches,  but rather failure will include the entire snowpack.