Provo

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  3

  The high winds are drifting snow and adding more stress to the snowpack. They will be increasing throughout the day until midnight tonight where they should reach gusts near 90 mph.

  Yesterday the skies cleared, and the winds died down and we were able to see what had happened Monday. The entire range had been worked by the winds, and signs of wind drifted snow could be found at every aspect at every elevation band. Many slopes with slabs of wind drifted snow had been naturally triggered by cornice fall adjacent. Today I would continue to expect to find wind slabs at all upper elevation slopes and north, east and west-facing mid-elevation slopes. I would also expect to find some isolated wind slabs on south-facing mid-elevation slopes and steep wind loaded terrain features at low elevations.

  As we add very high winds the south and westerly facing slopes will become increasingly scoured, and northerly and easterly slopes will continue to get loaded. These sustained strong winds have created stubborn hard slabs. These hard wind slabs can be more difficult to trigger meaning it could be the 4th or 5th skier on the slope that triggers an avalanche. They may also let you get further onto them before they break so that they break far around you.

  While the high north-facing terrain will be most suspect very high winds can scour, swirl and impact unconventional areas. Zones that had previously been protected could begin to see signs of wind drifted snow at all elevation bands.

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

• 

  Cornices

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1

  Yesterday multiple avalanches were reported from cornices naturally falling during high winds on Tuesday in the Central Wasatch. Today the winds will increase, and temperatures will be warm this will cause the cornices to continue to grow and their stability will be tested.

  Today's conditions make these cornices likely to continue releasing and could trigger adjacent wind slabs on steep slopes below them.

  If traveling near a cornice at all today, give them plenty of space both above and below. They can break back farther than expected while traveling on a ridgeline and could naturally trigger an avalanche above you if traveling below a cornice.

  Photo below of a natural cornice failure on S. Monitor that triggered the adjacent wind loaded slope below.

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  2

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

  • Southwest through Southeast: We have a weak layer of facets adjacent to a crust on the mid and upper elevations that is now between 2-5’ deep. 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 the south-aspects off yet.

  • West, North, and East: The early season October/November facets still exist at the ground, and we have now seen activity on them. Yesterday Drew saw an avalanche on South Monitor, a common repeater slope in the Central Wasatch, in which a natural cornice fall triggered a wind slab that appeared to step-down to early season facets at the ground. These repeater slopes, or slopes that have previously avalanched this season, are the most suspect. They have an overall shallower snowpack, therefore they are more likely to still possess those weak early season facets. Today as we add more load in the form of wind to these repeaters, and have a similar set-up to Tuesday, I would expect to see more activity on this layer.

  Since the New Year, we got a lot of snow, nearly 100” inches, following that snowfall we have gotten extremely high winds. This combination of snow available for transport and the consistent high winds has begun to tip the scale when it comes to these early season facets. The increased winds today into tonight will just continue to add more stress to this persistent weak layer and steep, north-facing, thin terrain will continue to be especially suspect to step down into the facets at the ground.

  Photo of South Monitor bowl avalanche that stepped down to the early season facets. (Photo: Laurent)

  The take away: The persistent weak layers have made it possible to trigger an avalanche 2-4’ deep on nearly all aspects at the mid and upper elevations. I would avoid terrain steeper than 30 degrees and stick to low angle terrain with nothing steep above or adjacent to you.