Eastside Region

Problemi valanghivi

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta quota
  • Limite del bosco
  • Sotto il limite del bosco

  Probabilità

  Likely

  Dimensione

  1–2

  Wind speeds outperformed the forecast yesterday leading to substantial transport along ridgetops across the range. With an additional 2-5” likely today and ample amounts of loose surface snow already available for transport, we can expect the size and distribution of fresh sensitive wind slabs to grow substantially today as wind speeds increase still further. Remember, strong winds can distribute snow in unexpected ways. Don’t be surprised to find wind deposits at lower elevations and further down slopes than you may typically expect to find them. Today’s strong winds promise to impact terrain at lower elevations, and we expect to see wind slab development below treeline and in areas typically thought of as sheltered. It is also imperative to remember that even a small wind slab avalanche today might be enough to trigger a much larger and more destructive Persistent slab avalanche.  Be suspect of terrain features that encourage drifting such as the leeward sides of ridgelines, gully features, and cross-loaded depressions. Blowing snow, recent cornice growth, drifting, stiff hollow feeling upside-down snow, and textured, uneven snow surfaces are all signs of recent wind transport. Use these signs to identify and avoid slopes with recent wind deposits. 

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta quota
  • Limite del bosco
  • Sotto il limite del bosco

  Probabilità

  Possible

  Dimensione

  1–2

  Storm instabilities such as Storm slab avalanches and loose surface sluffs have gained strength since the storm cleared yesterday. However, it may still be possible to trigger a sizable storm slab avalanche today in sheltered areas and in steep unsupported terrain. Convex rollovers and slopes over 30° in steepness are potential problem areas. When in doubt, avoid being on or under avalanche terrain 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.

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta quota
  • Limite del bosco
  • Sotto il limite del bosco

  Probabilità

  Unlikely

  Dimensione

  2–3

  Field observations continue to highlight our weak structure; however, our mid-pack has gained strength.  It has gotten much harder for the weight of a skier to impact these lower weak layers. In many ways, this makes our persistent slab problem more frightening. The likelihood is very low of triggering one, but the consequences have to potential to be very high if you do.  Be cognizant of the wind today, areas that receive a heavy new load due to wind loading may be the areas where a large and destructive persistent slab avalanche could occur.  Steep, unsupported, and rock-strewn terrain and areas with shallower snowpacks that still held snow from November and December are also worth extra evaluation.  This is particularly true in the Northern part of the forecast area which held much more snow from our extended drought early in the season.  Don’t be afraid to investigate the lower reaches of the snowpack to see if old snow is present in the areas you wish to travel. This may mean digging all the way to the ground if you suspect old snow is present. Remember that persistent slab avalanches often propagate across and beyond terrain features that would otherwise confine surface instabilities such as wind or storm slab 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.