Bridgeport Avalanche Center

Avalanche problems

• 

  Deep Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  2–3.5

  Surface conditions are variable with ice crust, breakable crust, mank, crud, hot pow, wind stripped sastrugi with the occasional pocket of cold powder still available.  But under these variable conditions remains a weak layer in specific locations, that is stubborn to trigger.

  This is a particular hard layer to predict avalanches, as it is over a meter deep in uniform terrain, and could be less in certain spots and easier to trigger.  There are no signs on the surface to clue you in that it exists, until you're in the avalanche, and a big one at that.  You may be able to dig a pit and your tests may clue you in to it, or not. Maybe you dug it in a spot where its not particularly reactive.  This layer is most reactive in Below Tree Line and Near Tree Line zones on mostly shaded North facing slopes or protected by trees.

  We haven't seen any new natural or human triggered avalanches in the past few days in our area. But the pit data suggests its still present.   Terrain management is the key to deal with this problem. Keep your slope angles low, stay out of consequential terrain, have a good plan with good knowledgable partners that have similar risk assessment skills and risk tolerance.

   

   

  

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1–2

  On Wednesday Feb 19, we had strong dominant West-South-West winds moving surface snow in our area.  This wind was strong enough to strip snow in spots and redeposit in protected leeward locations.  The stripped snow is easier to identify than deposited slabs are.  Look for striping patterns on the leeward surfaces. Also spindrifts and horsetails in the air are a tell tail sign that active redistribution of snow is happening.  Avoid start zones on leeward slopes that look pillowed or fat with snow, especially on convex rollers. 

  Yesterday we had a weaker North-East wind, that re-redistributed some snow back onto the opposite direction slopes. Keep in mind, it was less strong but capable of loading small catchment zones in protected alpine terrain, particularly in rocky couloirs (steep chutes).

  This avalanche problem is less of a concern for deep burials, but more of a concern for 1) knocking you off your feet in consequential terrain or perhaps pushing you into a terrain trap 2) Also these smaller avalanches can step down onto the deep persistent weak layer below and trigger a much larger-unsurvivable slide.