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

  Possible

  Dimensione

  1–2

  Modest snow totals and extreme winds during the evening hours have likely created fresh wind slabs in leeward catchment zones at all elevations. 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. It will be crucial to conduct your own localized assessments. While most fresh deposits will be small, there may be potential to find more sizable and concerning wind slabs in isolated areas. Large drifts, recent cornice growth, hollow upside-down feeling snow, and uneven snow surfaces are all clues that indicate nearby wind deposits. Remember, extreme 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. 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

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

  Probabilità

  Possible

  Dimensione

  1–2

  Over the last couple of weeks, forecasters have been tracking the presence of well-developed facets and facet crust combos in the upper snowpack. While our recent meager snow accumulations are not likely to overwhelm these weak layers on their own, the presence of persistent grains is likely to add to the size and sensitivity of reactive wind slabs. It will be possible to see shallow wind slabs stepping down into old snow layers creating larger, more destructive avalanches. While the distribution of concerning areas overlaps with our wind slab problem for now, we expect to see this change over the coming days.  As we see more substantial snowfall accumulations, triggering a persistent slab avalanche will become more likely. Northerly and easterly aspects are of greatest concern, particularly in steep unsupported terrain on shaded aspects and in areas where recent wind events have added cohesion to snow on the surface. Persistent slab problems challenge our patience. Managing this problem will require extensive evaluation and deliberate terrain choice. 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.