Salt River and Wyoming Ranges

Avalanche problems

• 

  Wet Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Unlikely

  Size

  1–2

  Wet slabs remain a concern today due to continued warm temperatures, especially at middle and low elevations. A week of daytime temperatures in the 40s and sun allowed free-flowing water to move through the snowpack and pool on crust layers. While it is unlikely for a human to trigger a wet slab, water moving through the snowpack can have a lag effect causing these avalanches to happen days after a heating event. Steep southerly aspects, especially around rock features, are where you're most likely to encounter this problem. The last known wet avalanche occurred on 3/19 in the Snake River Range on steep rocky terrain and broke into deeper wet layers near the bottom of the slide path. 

  Managing this problem can be difficult. Pay attention to signs of warming. If you've found an unsupportable, mushy snowpack consider staying off of and away from large or consequential avalanche paths with similar characteristics. Don't let a refrozen crust catch you off guard either, remember that water and heat remain deeper in the snowpack. Today's cloud coverage and slightly cooler temperatures will continue abating this avalanche problem. Until then, colder snow and better riding conditions can be found on the north half of the compass. 

   

  

• 

  Deep Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  2–3

  Weak snow that formed in December persists at the base of the snowpack across the entire Greys River forecast zone. However, the thickness of the hard slabs that overlay this weak snow varies based on geographic location. In the middle and upper elevations of the Salt, Snake River, and deeper portions of the Wyoming Range, these weak layers are buried 3-5+ feet deep making it difficult for a human to impact them. In shallow parts of the forecast zone, such as the far eastern side of the Wyoming Range, these slabs are only 2-3 feet thick making it possible for humans to trigger avalanches on the buried weak layers. Shallow, rocky, and unsupported terrain on the north half of the compass is where this problem has been most active. Keep in mind that a large trigger such as a cornice fall could trigger one of these very large avalanches, even in areas where the snowpack is deep.

  Careful snowpack evaluation is required in the Greys River zone due to variable snow depths. Probing or digging can provide useful information about the depth of the weak layers preserved at the bottom of the snowpack. This evaluation is critical if you are riding in a shallow part of the zone. A total snow depth of less than 6 feet (200cm) is a red flag.

  The last reported human-triggered avalanche involving deeply buried weak layers occurred on March 9th on the far eastern side of the Wyoming Range.