Salt River and Wyoming Ranges

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1–2

  Recent snow combined with gusty SW wind around 20 mph formed reactive slabs 1-2 feet deep. Slabs could be up to 3 feet deep in isolated areas in the upper elevations. Several poor interfaces exist near the top of the snowpack resulting in unstable recent snow, as seen yesterday with numerous avalanches above 7500’ primarily on steep northerly aspects. Expect to see similar reactivity today and keep in mind that avalanches will be larger or more dangerous in the upper elevations due to higher amounts of recent snow and stronger wind. Avoid wind loaded terrain where you encounter obvious signs of wind drifted snow including cracking or stiffened surfaces and large pillows. Look for wind drifted snow on leeward slopes off ridgelines and cross loaded slopes adjacent to large wind funnels such as large creeks and canyons. Confined features such as couloirs can also entrain more snow even if small avalanches are triggered. In addition, watch for increased activity on slopes facing the sun due solar influence by the afternoon if skies clear.

  

• 

  Deep Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Unlikely

  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 Salt, Snake River, and deeper portions of the Wyoming Range, these weak layers are buried 3-5+ feet deep making it unlikely 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 more 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 you are most likely to impact weak layers. 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.

  Identify thin areas in the Greys River zone as you ride. 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 5 feet (150cm) 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.