Continental

Problemi valanghivi

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  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta quota
  • Limite del bosco
  • Sotto il limite del bosco

  Probabilità

  Likely

  Dimensione

  1–2

  Rain on snow will continue today with the freezing level slowly dropping back below 1000'.  Wet loose avalanches will be likely in steep low elevation terrain.  Many steep slopes at low elevation have already had wet loose activity occur.  Additional slopes may fail today depending on the intensity of rain that occurs.  

  Avoid steep terrain that is rain saturated, this includes slopes above you.

   

   

   

  

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta quota
  • Limite del bosco
  • Sotto il limite del bosco

  Probabilità

  Likely

  Dimensione

  1–2.5

  Strong southeast winds overnight, rising temperatures and heavy snowfall above 2000 feet are all combining to create dangerous avalanche conditions today.  The 12 mile weather station has reported 1.46 inches of rain in the last 24 hours as of 4:30 this morning.  This will translate to 12-16 inches of new snow at upper elevations.  Wind speeds at the Thompson Pass gap were gusting to mid 40's last night and likely exceeded 60 mph on ridge tops in wind exposed terrain.  Expect for the new snow to be unstable today with human triggered avalanches likely that involve the new snow.  Wind drifted pockets of unstable new snow up to 3 feet in depth could exist.  

  An additional 8-12+ inches of snowfall is expected in the next 24 hours that will continue to put stress on the upper snowpack, keeping the avalanche hazard elevated.  Human triggered avalanches that fail within the new snow have the potential to step down to a buried weak layer and produce very destructive, unsurvivable avalanches. (see problem 2)

  Terrain selection will be key for safe travel in the mountains today.  Conservative terrain choices are recommended.  Only expose one person at a time to avalanche terrain, avoid travelling alone, maintain good communication with your group, and group up well out of the way of possible avalanche runout zones.

  

• 

  Deep Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta quota
  • Limite del bosco
  • Sotto il limite del bosco

  Probabilità

  Likely

  Dimensione

  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.

  Continued heavy snowfall will be increasing the sensitivity of this layer where it exists.  It is possible that some areas have failed naturally overnight, while others are waiiting for a trigger.  The depth and structure of this layer make identifying it challenging at this point even for experienced users.