Salt River and Wyoming Ranges

Avalanche problems

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Unlikely

  Size

  2–3

  Our most concerning persistent weak layers sit near the middle and base of the snowpack. An avalanche failing on one of these layers has the potential to be very large, three or more feet thick, particularly in open and well-connected terrain features. Persistent weak layers can produce avalanches many weeks after they are buried. Minor warming  or small amounts of new snowfall can make these layers sensitive to human triggering. They can break wider than you might expect and may be triggered remotely, from gentle terrain next to a steeper slope. 

  Trigger points are an important consideration with these avalanches. You can reduce your chances of trigger an avalanche by avoiding slopes with shallow, more southerly areas where you can more easily impact the weak layer. Trigger points are most common in alpine (or alpine-like) terrain:  very steep (over about 35 degrees), rocky, and wind-affected.  Pay attention to what's below you—look for trees, rocks, gullies, and other terrain traps that could turn even a small avalanche deadly.

  

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1–2

  Many small wind slab avalanches where observed 24-48 hours ago just north in the Tetons. In the past 24 hours, moderate wind shifted to the north and has likely loaded and cross loaded aspects with a southern component.  Wind slabs formed from light to moderate, variable winds may remain reactive underfoot today. Wind-affected areas can be identified by drifts, cornices and pillows along ridge crests, or stiffened snow surfaces. Recent snowfall and cold temperatures have allowed loose snow to accumulate beneath cliff faces and gullies. These sluff piles can be triggered much the same way as smoother wind slabs and may also add strain to buried weak layers.

  Steep slopes where wind slabs and persistent weak layers overlap are where you're most likely totrigger a large avalanche. Wind-affected snow may also be buried beneath recent, lighter snowfall. Slopes with stiffer snow near the surface—whether from wind-loading or "spin drifting" below large cliff faces—are more likely to produce big avalanches than areas where the surface is loose powder.