East Slopes Central

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1–2

  Strong winds and increasing precipitation will create new wind slabs Saturday.  Feel for firm or hollow sounding snow and generally avoid open slopes steeper than 35 degrees above treeline.  Firmer slabs may form on a variety of aspects and further downslope than usual due to the strength of the winds, making shallow wind slabs possible at mid-elevations.  Also avoid freshly formed cornices along ridgelines, making sure to give them a wide berth.  Cornices near the Cascade crest are larger and more sensitive to human triggers over the last few days.  They are likely to break off and may trigger avalanches on the slopes below. 

  Public observations (thank you!) report shallow wind slabs releasing on NYE.  Weak snow buried above the 12/21 crust may have been the interface in the Salmon la Sac area.  This interface may still be sensitive Saturday as we continue to add load to the snowpack. A natural wind slab released below cliff bands in the Mission Ridge area. 

  Small loose wet avalanches are again possible in elevations around the rain/snow line Saturday.  If you find yourself sinking in wet snow more than ankle-deep or see natural warning signs like pinwheels or rollerballs releasing from very steep slopes, move to lower angle terrain.  Even small loose wet avalanches can knock you off your feet and can cause injury in the wrong piece of terrain. 

  

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  2

  Persistent slab avalanches are still on our radar as our storm cycle ramps up over the weekend. A weak layer of sugary snow sits atop an icy crust from back in early December.  This structure is similar to that involved in past avalanche accidents in this area and continues to warrant respect. The consequences of triggering avalanches are serious as they could easily bury or kill you. These dangerous and surprising avalanches can catch even the most experienced backcountry travelers. The best way to stay safe is to avoid the type of terrain where you are most likely to trigger one. Keep your distance from slopes 35 degrees and steeper that are open enough and tall enough to produce large avalanches. Watch for obvious signs of instability like recent avalanches, whumphing collapses, or cracks shooting through the snow.

  Look for weak snow just above a thick melt-freeze crust roughly 1.5ft to 3ft below the surface, above 5,000ft. We suspect this is more problematic in the northern half of the zone and closer to the Cascade crest where dry snow exists above these weak layers. The most dangerous slopes will be at the higher elevations, in steep unsupported and rocky terrain.  As recently as the 27th, observers performed snowpack tests that indicated propagation is still possible with this layer of concern. We found it 3ft below the surface on an east aspect at 6,600ft in the Near Treeline band near Chickamin Ridge in the Chiwawa Drainage. These layers are not a concern where you find a stout crust near the surface, such as areas further south and at lower elevations.