Continental

Avalanche problems

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1–2.5

  Dangerous avalanche conditions will continue today. A warm storm with ample amounts of moisture has been adding to the 2 feet of recent snowfall accumulation in mid and upper elevations through our forecast area.  Above 2000 feet, wet heavy snow has been accumulating on top of unconsolidated older storm snow for the last 48+ hours. Upper elevations are expected to have received 2+ feet of additional snow on top of an already thick storm slab. Moderate to strong ridgetop winds have likely redistributed the recent snow into drifts or slabs up to 5 feet thick. These deep and top-heavy storm slabs will create dangerous conditions. Human-triggered avalanches 1-3 are likely to be triggered in terrain over 30 degrees today. 

  Today is a good day to stay on conservative terrain while the snow settles. Identifying and avoiding avalanche terrain (steeper than 30 degrees) is your best defense against the hazards present today. Remember, avalanches from above can run into lower-angle slopes below. 

   

   

  

• 

  Deep Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  2–3

  A weak layer of snow that formed during the extended sunny weather in March is at or near the breaking point.  This layer does not exist everywhere but has been found above 4000 feet on shaded aspects.  Terrain that is commonly wind-protected will be areas where this layer is most likely to persist.  Where this layer exists VERY DANGEROUS AVALANCHE CONDITIONS EXIST.    Slopes that have this weak layer could be triggered by a skier or snowmachiner and produce avalanches 3-5 plus feet in depth.

  Our last clear day of clear weather on Tuesday 4/15, saw avalanches triggered at this layer by snowmachines, skiers, hikers, and helicopters.  Multiple close calls were reported, including this report from Billy Mitchell (see  avalanche observation here) which we are grateful this person was humble enough to report and document well so others can avoid triggering one of these deep slabs.

  Heavy loading has increased the sensitivity of this layer where it exists.  It is possible that some areas have failed due to this loading, while others are waiting for a trigger.  The depth and structure of this layer make identifying it challenging at this point, even for experienced users.

  

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1–2

  Significant amounts of rain and wet snow have fallen at lower elevations.  Natural and human-triggered wet loose avalanches are likely. Expect to find a saturated snowpack below 1500 feet in all areas. These saturated low elevation slopes could potentially fail to the ground. Above 1500 feet, expect to find wet and heavy snow accumulations that will contribute to wet loose slides. Even small wet slides can be hazardous due to their high density.  Don't underestimate the potential for a small avalanche to knock you down or over a hazard below.  If the sun comes out there will be additional wet loose activity on higher elevation sunny slopes. Direct sunshine will rapidly increase the hazard on slopes with significant amounts of heavy, wet snow.