West Slopes Central

Avalanche problems

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  1.5–2.5

  Dry slab avalanches will grow in size and become more dangerous and reactive as the day progresses. The day may start out with Considerable avalanche danger, but expect the danger to rise to High as more snow falls and temperatures increase. Storm slab avalanches could fail in the new snow, which may be as deep as two feet at the upper reaches of our forecast zone. However we've seen a lot of avalanche activity lately in the last few days with most avalanches occurring one to two feet deep. These layers may not be completely healed by the time the new snow comes in, so avalanches could fail on these older layers, making upper-elevation avalanches three or more feet deep. Earlier in the day avalanches could be smaller, but they will increase in size as our snowpack grows. Smaller storm slabs could occur in upper portions of below treeline areas, before the snow gets wet. 

  Rising temperatures have two important factors to be aware of, which generally don't mean anything good. Firstly, relatively cooler, lighter, snow will fall before heavier, denser snow that comes with the temperature increase will fall on top, leading to an upside-down snowpack. Upside down snow tends to be unstable, where the, lighter, weaker underlying snow fails under the weight of the heavier snow on top, and an avalanche occurs. This is the perfect setup for natural slab avalanches, which you can expect to see as the snow builds up. The other concern with rising temperatures is rain, which is discussed in the next avalanche problem.  For the storm slab avalanche problem, we've got a dangerous setup that will continue to grow on Thursday. Natural avalanches are likely and human triggered avalanches are very likely, so traveling in avalanche terrain is not recommended. 

  

• 

  Wet Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  1.5–2.5

  Wet snow avalanches will develop into a dangerous problem as the day progresses. Snowlines are forecasted to rise to 6500ft by Thursday evening. As the rain slowly encroaches on the dry snowpack at higher elevations, your dry snow avalanche concerns will transition to wet ones. They may start with small wet loose in the upper reaches of below treeline areas, where previous low-density snow existed. The wet loose avalanches will slowly shift higher, reaching all the way into above treeline elevations as the rain reaches higher elevations. As more rain falls and percolates into the snowpack, unpredictable wet slab avalanches are expected. There may also be glide avalanches running on steep slopes with smooth, underlying bed surfaces as well.

  The wet slab avalanches could fail as deep as the dry snow avalanches, or possibly even deeper. They could be a mix of wet and dry snow, progressing to more wet as the day progresses. Wet slab avalanches are not something to tiptoe around, and this is a day where it's a good idea to stay off steep slopes and runouts beneath avalanche paths.