Blues

Problemas de aludes

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta montaña
  • Límite del bosque
  • Bajo el límite del bosque

  Probabilidad

  Possible

  Tamaño

  1–2

  The latest storm cycle which started on Monday and continued into early Wednesday morning brought over a foot of snow to the Southern Wallowas and Blues and about half that amount for the Northern Wallowas and Elkhorn mountains over the same time period. This new snow was accompanied by winds from the southwest, west, and northwest, and slightly rising temperatures. The new snow, coupled with the moderate (stronger at some locations) westerly winds, has created windslabs on leeward northeast, east, and southeast facing terrain at all elevations. This new load of snow is poorly bonded to the older snow it rests upon. The reason for the poor bond at the new snow/old snow interface is the presence of surface hoar and near surface facets on the old snow surface. These now buried persistent weak grain types that the new snow rests upon will inhibit the bonding process at the new snow/old snow interface resulting in unstable windslabs. Yesterday, while ski touring in the Northern Elkhorns, I observed wind deposited snow and windslab formation on all the east and northeast slopes I traveled upon from trailhead to ridge top. While ascending a northeast facing ridge near the Anthony Lakes ski area I heard several collapses or "whumpfs" just above 8000' .  I also observed instability in my snow pits. My Snowpit columns were failing with an easy amount of force at the new snow/old snow interface accompanied by propagation. Propagation occurred on a snow pit that was dug at about 8400' . At this location the new snow ( windslab ) was about 10" thick. I also did many ski cuts on small, steep, terrain features but was unable to trigger any avalanche activity. That said, because of other red flags I observed on my ski tour I chose to descend on safe slopes less than 30 degrees steep. Even though I did not observe avalanche activity, I believe that today we are in a period of heightened avalanche danger. I also think human triggered avalanches are possible on steep, leeward facing terrain near and above treeline. If you choose to recreate on terrain steeper than 30 degrees today, evaluate the slope very carefully before proceeding. If you observe hollow sounding/feeling snow, collapses, whumpfs, or shooting cracks, these are red flags that are warning you that the slopes you are traveling upon are unstable and could avalanche. 

  

• 

  Deep Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta montaña
  • Límite del bosque
  • Bajo el límite del bosque

  Probabilidad

  Unlikely

  Tamaño

  1–3

  The persistent slab problem that we have been seeing and discussing all month long is still being observed but now resides deeper in the snowpack,  more than a meter below the snow surface, and close to the ground. Because these persistent weak layers are so deeply buried in a snowpack that is now 5'-6' deep, especially at and above treeline, they are difficult to trigger by the weight of a human. A snowmobile rider is much more likely to trigger one of these low  likelihood, but extremely high consequence, deep slab avalanches. These large and consequential slabs are most likely triggered from shallow areas of the snowpack near wind blown ridges and rocky areas. A deep persistent slab can also be triggered from below. It is advisable to stay off of and out from under slopes steeper than 30 degrees while "persistent slab" and "deep persistent slab" instability is being observed and discussed in the advisory.