Continental

Avalanche problems

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1–2.5

  A stormy April continues with the next round of snowfall already affecting our area.  Snow was falling at the coast at 5:30 this morning but is expected to turn to rain as the freezing line is expected to steadily climb to 2500'.  Winds will also be on the increase with 60 mph gusts from the south east during the day.  Temperatures, snowfall and wind intensity look to peak tonight with gusts to 75 mph and 12+ inches of fresh snow expected by Thursday morning. 

  This new snow is falling on 12-18 inches of snow that fell on the 13th-14th.  Slope testers yesterday found the new snow to be stubborn to triggers in moderate terrain.  However, several human triggered avalanches were reported and observed yesterday in steep terrain with some stepping down to deeper layers in the snowpack (see problem 2).  Expect the surface snow to become more sensitive to triggers today as temperatures warm, creating upside down storm slabs, and strong winds create sensitive pockets of wind loaded snow.

  Expect dangerous avalanche conditions to exist today as the snowpack receives continued stress.  Conservative terrain choices are reccomended.  Avoid exposing more than one person at a time to avalanche terrain, maintain good communication within your group, know your safe zones, and be sure they are well out of the way in case you do trigger an avalanche.  

  

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  2–3

  A weak layer of snow exists 2-4+ feet deep in our snowpack in some locations on shaded aspects above 4000'.  

  Prolonged sunny skies in March formed surface hoar and near surface facets.  At the tail end of the nice weather, moderate and fairly widespread North winds kicked up that knocked over and destroyed the surface hoar in the majority of areas.  Near surface facets remained, however these were mitigated to some extent by very warm temperatures on the last day of the high pressure along with freezing line rising to possibly 5000' at the beginning of the April storms.  This warming process deformed facets at low and elevations below 4000'. 

  The weather process described above has made the distribution of this layer spotty.  Continued loading of the snowpack will be moving slopes closer to the breaking point where this layer exists.  When this layer has been found, it has been challenging to identify due to its depth although a clean shear exists.  This combination makes assessment very difficult even for experienced users and could be easily missed in hasty pits or even by guides that are moving quickly to gather data.

  Multiple skier, hiker and helicopter triggered avalanches were reported that likely involved this layer.  One being a ski tourer on Billy Mitchell (see  avalanche observation here) and another being a heli group on The Island in Wortmans.  The pattern of the presence of this weak layer and these human triggered avalanches is so far understood to be above 4000' and on NW-NE aspects.  Caution is strongly advised as a dangerous snowpack exists in some locations.

  

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1–2

  Rain on snow is expected to occur up to 2500' by mid day today.  Wet loose avalanches will be likely in steep low elevation terrain if rain becomes heavy and is able to saturate the snowpack.  Pay attention to how wet the surface snow is if you are travelling at low elevations today.  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 has more than 6 inches of wet snow or in areas where the snowpack can't support a person's weight.