Continental

Avalanche problems

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1–2.5

  Temperatures look like they have topped out for this storm system yesterday afternoon and will be on the slow decrease until Saturday morning.  Above freezing temperatures remain on the south side of Thompson Pass, and have fallen to 32° on the north side.  The 12 mile weather station reported an addtional .27" of rain in the last 24 hours bringing the storm total to 2.34" for that location.

  Even though temperatures are forecasted to be lower today, the main avalanche concern below 3000 feet will continue to be wet loose avalanches.  Natural activity is expected to be less than yesterday, however human triggered activity is still likely.  Warmth in the snowpack can remain longer than you may expect, even as temperatures hit the freezing mark .  Roller balls or snow snails are a visual sign that wet loose conditions are present.  Pay attention to the terrain you are traveling on. What is above and below you?  The size of wet loose avalanches directly coorelates to the size of the slope above you.  The consequences correspond to what is below you, where will a wet slide potentially take you?  Is there a gully or terrain trap that could pile up deeply? Cliffs? Thin rocky areas?  The sensitivity relates directly with how saturated the surface of the snow is, this can be tested by putting your hand into the snow to feel how far down the wet or moist snow goes, and where the dry snow begins.  This problem is expected to remain steady through the day with continued rain on snow.

   

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1.5–2.5

  The snow line climbed higher during the day yesterday with Thompson Pass receiving mostly rain at road level during the day.  The Nicks station received an additional 2-3" bringing the storm total to 18" for that location.  Winds were moderate yesterday from a variety of directions, but are forecasted to be strong at ridgetops today out of the SE creating deeper slabs in specific locations. An additional 2-4 inches of snow is expected above 3000 feet today.

  Human triggered storm slab avalanches remain likely today above 3000 feet in terrain steeper than 30°.  New snow over the past 72 hours has been steadily building slabs to 2 feet in depth with wind loaded areas of 3-4 feet possible near upper elevation ridgetops.  This new snow started out as dry and cold, and was deposited on a variety of very hard wind damaged surfaces.  As the storm progressed, temperatures increased sharply; this has created top heavy storm slabs that are likely sensitive to human triggers especially in wind loaded areas.  Our snowpack has undergone a major change in the last few days and needs time to heal.  Conservative terrain choices and cautious route finding will be critical for safe travel in avalanche terrain today.

    Pay attention to the depth of new snow, along with its sensitivity and how well it is bonded to old snow surfaces.  Sensitivity can be judged by watching for red flags such as shooting cracks, collapsing, and using small test slopes to jump or ride on to watch for failure.  Bonding can be assessed by employing simple hand shear tests to check for bonding at the new/old interface as well as looking for density changes within the new snow that could act as a failure plane.  These should be done in various areas since the underlying bed surface is currently extremely variable and bonding is likely to vary.