Provo

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  3

  Even though the winds have finally begun to die down, today wind slabs will continue to be on all aspects of the compass and likely human triggered on steep terrain and could continue to run naturally.

  Everywhere I traveled yesterday, every aspect and every elevation, from the trailhead to the ridgeline I was able to find signs of wind drifted snow. While the fresh slabs of wind drifted snow will be concentrated on upper elevation north facing terrain, they will not be isolated to that terrain. The southwest winds worked the entire range, and heavily influenced mid-elevation slopes as well. Expect to find wind slabs at all mid and upper elevation slopes, and even steep wind loaded terrain features at low elevations.

  The other tricky thing about this wind drifted snow is the varying sensitivity it could possess. Winds were howling yesterday, and with more snow available for transport we could have a soft slab, hard slab, soft slab sandwich on our hands. I would expect to see extremely soft slabs, easily triggered remotely from a distance in some areas and/or extremely firm, and stubborn hard slabs that are more difficult to trigger in others.

  Today look for slopes with any signs of wind drifted snow, such as cracking, hollow sounds, and pillow-shaped snow, and avoiding those slopes.

  A photo Greg took yesterday on 10420 in Big Cottonwood Canyon of a fresh dense wind drift sitting atop the lower density snow.

  The CORNICES are getting huge, and just continue to grow. Yesterday while I was out I saw signs of growing cornices and signs of natural cornice release. These cornices are likely to continue releasing and could trigger adjacent wind slabs on steep slopes below. If traveling near a cornice, give them a wide berth as they will break back farther than expected if traveling above them and could naturally trigger an avalanche above you if traveling below them.

  A photo of the large growing cornices from the Reynolds Ridgeline yesterday where they continue to release naturally.

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  2

  We have two persistent weak layer issues, that are collectively impacting the entire compass:

  Southeast through Southwest: We have a poor snowpack structure that includes a layer of weak facets adjacent to a crust on the mid and upper elevations. This layer could now be anywhere between 2-5' deep in the snowpack. While we haven’t seen any recent activity from this layer, as we continue to add more load in the form of wind and snow I am not ready to write it off yet.

  West, North, and East: We haven’t talked about the October/November facets in a while, and overall considered them dormant, but as we continue to add increased load areas that have previously had avalanches, known as repeater slopes, this season will become increasingly suspect. Yesterday I went out to an avalanche on East Reynolds, a common repeater slope, to investigate the layer which the avalanche failed on. Most of the slide path was blown back in from the recent wind and cornice fall, but we were able to find select areas that were deeper than the new snow/old snow interface. While I cannot confirm that this was the November/October facets, it is obvious that part of that avalanche did step down into a deeper layer of facets.

  The Cottonwoods have gotten a ton of new snow, nearly 100” inches in combination with strong winds. These two things together put a lot of stress on the snowpack and if these early season facets were to begin to fail again, now would be the time. Steep, northerly-facing, thin and rocky areas are going to be especially suspect to steep down into a deeper layer and I would continue to investigate repeater slopes.

  Bottom Line: With either persistent weak problem, it could be possible to trigger an avalanche 1-3' deep on nearly all aspects at the mid and upper elevations. For this reason, I would avoid terrain steeper than 30 degrees, stick to low angle terrain with nothing steep above or adjacent to you.