Eastside Region

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  1–3

  As winds increase along the ridgetops this morning, leeward avalanche start zones will be actively loading with wind-deposited snow. In this scenario avalanche hazard is increasing in three ways at once :

  • Wind-drifted snow tends to form cohesive layers ideal for slab avalanche release.
  • Wind deposition adds load to the slope more rapidly than snowfall alone pushing the snowpack nearer to failure.
  • Wind deposits are deeper than the surrounding new snow layers so the resulting avalanche may be larger than expected.

  Plumes of blowing snow are visual confirmation that wind slabs are building and can be observed from a safe distance before being exposed to the hazard. Other red flags for wind slabs include areas of hard hollow feeling snow, shooting cracks, or a textured styrofoam-like snow surface.

  With higher ridgetop wind speeds loading can sometimes occur mid-slope where wind speeds are less intense than on the ridge lines. Large to very large Natural and Human triggered avalanches are likely today and avalanches may run long distances and into lower angle, or treed terrain you may typically think of as “safe”. Be cognizant of what is above you today, travel in and below avalanche terrain is not recommended.

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  1–2

  Storm slabs generally result from density changes within the recent storm snow created by changes in temperature and rate of snowfall during the storm. We have both of those indications in weather data today. If you are in the mountains look out for heavier cohesive snow over softer loose snow. Avoid being on or under slopes over 30° in steepness today and be cognizant to your exposure to terrain features that increase the consequences of avalanches. this may include exposed areas under rooflines in town. Be wary of overhead hazard today and avoid being in or underneath avalanche terrain.

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  2–3

  While our recent storm systems provided the forecast area with a much-needed blanket of snow it has also brought about a new set of challenges. Make no mistake we are now dealing with a weak and complex snowpack. While this load may have been enough to tip the scales on its own in some areas, in others the snowpack may still be hanging in the balance. A relatively small storm or wind slab avalanche or the weight of a skier might be all that is needed to tip the scales and trigger a large destructive avalanche.  Persistent problems require persistent patience and extensive evaluation. High levels of uncertainty remain around the precise distribution and reactivity of the persistent slab issue. Northerly and Easterly facing terrain are our most likely problem areas.  Don’t be afraid to investigate the lower reaches of the snowpack to see if old sugary snow is present in the areas you wish to travel. Remember that persistent slab avalanches often propagate across and beyond terrain features that would otherwise confine surface instabilities such as wind or storm slab and in some cases persistent slab avalanches can be remotely triggered from adjacent slopes. Give yourself a wide safety margin, be wary of hazard that may reside above you, and use terrain choice to limit your exposure.