Salt Lake

Avalanche problems

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  2

  Throughout Utah, dangerous slabs of snow hang in the balance on many aspects and elevations from west to north to easterly facing terrain at the mid and upper elevations. With every bump in wind speed and or new snow (water) added to our fragile snowpack, we continue to wait for the snowpack to become unglued. This morning we added two huge new stressors to this fragile snowpack in the form of elevated winds and new snowfall. We don't know if this is the tipping point that will cause the snowpack to become unglued, but we do know that the avalanche danger and likelihood of avalanches will be on the rise.

  The most likely places to trigger a slide in that persistent weak layer are slopes with some wind-loading especially on more northerly facing slopes with the weakest snow. The little extra weight of wind drifted snow today keeps the buried facets stressed and ready to fracture.

  If you're new to dealing with Persistent Weak Layer issues, head to a low angle slope with nothing steep overhead or adjacent to you and pull out the shovel and dig to the ground. You will see strong snow over very fragile and weak faceted snow. Today, human-triggered avalanches are very likely, these avalanches can be large enough to catch, carry, bury, and kill a person. Given the new snowfall, elevated winds, and poor snowpack structure I would avoid any terrain steeper than 30 degrees, with any steep terrain above or attached to it. Today is not the day to push it.

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  2

  The winds have been cranking now for two days, early this morning Hidden Peak saw wind speeds over 80 mph. These strong winds in combination with a few inches of new snow over will have drifted snow and formed fresh slabs. The winds didn't have a ton of new snow to move around yesterday, but with such high winds, any snow that was available for transport will have been transported. The issue with yesterday's freshly formed wind slabs is they will likely be hidden under a few inches of new snow from this morning and harder to identify this morning.

  Know that shallow slabs of wind drifted snow will exist on mid and upper elevation terrain features that snow could be deposited, such as ridgelines and gullies.

  Elevated winds this afternoon will continue to form both soft and hard slab avalanches in mid and upper elevation wind drifted terrain. As the winds continue to blow, these slabs will become more firm and cohesive. This can allow you to travel out farther onto the slope before it breaks, and can fail larger and wider than expected. High winds can deposit snow on all aspects but give west through north through east extra caution, as triggering an avalanche that initially fails in the wind-drifted snow will likely break down more deeply into the weak faceted snow below.

  Photo from Cardiff Fork of obvious wind loading occurring. PC: M. White

  Look for any slopes with signs of wind drifted snow, and avoid those slopes.

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1

  Today we should be getting 6-12" of new snow by the time all is said and done. While snow totals are important, what we truly pay attention to is at what RATE that snowfalls and how quickly it loads the snowpack. We call this precipitation intensity, and if those rates stay elevated or increase throughout the morning we could see the avalanche danger spike and more new snow avalanches occurring. Keep an eye on the sky, if the snow rate rapidly increases you know the danger is on the rise.

  The new snow should produce loose snow sluffs or point releases, primarily in upper and mid-elevation terrain features protected from the wind. These typically break at your feet and not a major concern. Terrain traps like gullies or creeks can cause these sluffs to pile up debris much deeper and could be enough to bury a person. Pay attention to the terrain you are traveling above.