Eastside Region

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1.5–2.5

  Reactive wind slabs will grow in size and sensitivity today as the forecast region is impacted by strong winds and continued snow showers.  Be particularly cautious in areas with higher snow totals from yesterday’s storm. This may include the northern half of the forecast area, higher elevations, and areas closer to the crest.  While wind slabs will be more concerning near and above treeline, extreme winds can distribute snow in unexpected ways. Don’t be surprised to find fresh wind deposits at lower elevations and further down slopes than you may typically expect to find them. Large drifts, recent cornice growth, hollow upside-down feeling snow, and uneven snow surfaces are all clues that indicate nearby wind deposits. Be suspect of terrain features that encourage drifting, such as the leeward sides of ridgelines, mid-slope rollovers, gully features, and cross-loaded depressions.

  

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1.5–2.5

  Field observations continue to highlight the presence of well-developed facets and facet crust combos in the upper snowpack. As we continue to see snow accumulate throughout the forecast area, we expect to see a cohesive slab form in more sheltered areas. This may be enough to overwhelm these weak layers on their own, however, our more immediate concern will be focused on areas where strong winds are stiffening surface snow. It will be possible to see avalanches breaking near the surface and stepping down into old snow layers creating larger, more destructive avalanches. Northerly and easterly aspects are of greatest concern, particularly in steep unsupported terrain on shaded aspects and areas where recent wind events have added cohesion to snow on the surface. Managing this problem will require extensive evaluation and deliberate terrain choice. When in doubt you can reduce your exposure by choosing to travel in more simple terrain with slope angles below 30°. Remember that persistent slab avalanches often propagate across and beyond terrain features that would otherwise confine surface instabilities such as wind or storm slabs and in some cases persistent slab avalanches can be remotely triggered from adjacent slopes. Give yourself a wide safety margin, be wary of hazards that may reside above you, and use terrain choice to limit your exposure.

  

• 

  Loose Dry

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1–1.5

  Storm instabilities may develop in areas with larger snow totals as snowfall rates increase throughout the day. Temperatures are expected to remain well below zero which will likely keep loose surface snow light and unconsolidated.  While this may limit the potential for significant storm slab development, loose surface sluffs may grow to concerning size in steep terrain sheltered from the wind.   Approach steep terrain over 30° today with caution and be cognizant of your exposure to terrain features that increase the consequences of avalanches. This includes road cuts, gully features, cliff bands, and mid-slope depressions.