Provo

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  2

  Winds have been strong, with some gusts nearing 100 mph at the highest ridgetops late last night. These powerful winds created wind drifts sensitive enough to avalanche naturally last night and into the early morning. With another 5-10" inches of snow overnight, winds will continue forming fresh wind drifts on top of ones formed yesterday. These drifts will be widespread near ridgelines at upper elevations but will also be found mid-elevations.

  Today the winds will let up for a few hours but will increase again this afternoon. The wind drifts will continue to grow, become more firm and connected, and more sensitive as the winds continue. Look for signs of wind drifted snow, such as soft pillows, cracking, and whumping and avoid them.

  Watch for sensitive cornices along upper elevation ridgelines, give cornices a wide berth as they can break back farther than expected.

  Photo of wind drifted snow on a ridgeline in Butler Fork in the Central Wasatch, look for these obvious clues and avoid being on wind drift. (Photo. G Gagne)

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  2

  Before the coming storm, we had great, light, soft powder skiing. On top of that great light powder, this storm deposited heavy, wet, warm snow. This creates a dense slab of new snow on top of that weaker layer of snow. The continued snowfall will create sensitive new snow avalanches today, and these may even be triggered at a distance.

  Human triggered avalanches are likely, as well as natural avalanches, especially at mid and upper elevations. Less snow fell at lower elevations but human triggered avalanches are possible. Pay attention to rapidly changing conditions, and watch for and avoid slopes with cracking, avalanching, even on smaller slopes.

  The upper layers of the snowpack are like a game of Jenga in which we have removed the bottom pieces and just keep adding more to the top. Additional load, such as wind drifted snow and new snow will cause it to topple over and create an avalanche.

  Video from the Central Wasatch representing a similar snowpack.

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  3

  This layer has been mostly dormant and has been gaining strength, but it is not forgotten. This storm is a good test of this layer.

  With enough snow and wind, it is possible that new avalanches may step down into the old persistent weak layer. An avalanche in the persistent weak layer is most likely on repeater avalanche paths, generally shallower snowpacks and in steep thin rocky terrain.