Continental

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1.5–2.5

  The primary avalanche concern continues to be triggering an old wind slab that formed between the peak winds of the 29-31st of January.  These wind slabs have been observed to be locked up and unreactive to human triggers for several days now.  The depth of these slabs is variable between just a few inches and several feet deep and exist in cross-loaded gullies, lee side of terrain features and a variety of aspects at upper elevations.

  The most likely place to find a wind slab that could still be triggered is where the slab is thinner and a person or machine is still able to break through the slab.  The sensitivity of these wind slabs will continue to decrease with time.  If a larger wind slab were to be triggered in steep terrain at upper elevations there could be a very small chance it could step down to the base of the snowpack creating an unsurvivable avalanche.  

  North winds are forecasted to be on the increase over the next couple of days.  With very little snow available for transport, the only anticipated effect of the wind will likely be knocking down of any facets that have formed at the surface.

  

• 

  Deep Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Unlikely

  Size

  3–4

  January was a month characterized by multiple extended periods of heavy snowfall above 2000' and heavy rain below.  In Valdez, 24.69" of water equivalent was recorded for the month, most of this being rain.  On Thompson Pass over 300" of snow was recorded at DOT camp.  This constant loading of the snowpack produced a major avalanche cycle on January 11-12 with dozens of D3 avalanches observed along Thompson Pass road corridor.  Deep slab avalanche activity stopped despite a continuation of heavy snowfall.  The exception to this was a few deep slabs that released in the Mt. Dimond area on the 19th.  

  The stormy month came to a climax with a storm on the 25-26th that produced 4-5 feet of snow on Thompson Pass and Valdez receiving 6.75" of water in 48 hours and 4"  in a single day.  After this storm there was very little natural avalanche activity.  A couple of days passed before the late January wind event started to redistribute the abundant amount of dry snow that was available for transport.  This loading of the snowpack tipped the scales in a few places and produced catastrophic full depth failure on North Ramp of Mt Francis, East face of Saphire, Goodwills, Mt Dimond area, Berlin Wall and the North Face of Three Pigs.

  These avalanches are very unlikely to be triggered by a human directly, but a larger load may be able to affect these layers,  Larger loads include a smaller human triggered avalanche that steps down and cornice fall.  These monster avalanches occurred on some of the tallest/most prominent peaks in the area on steep faces near the summit.  It would be wise to give extra caution to avoid climbing slopes with cornices.  With the weather pattern changing to one that is benign, the snowpack will slowly except the weight of the cumulative January snowfall.  The peak period of stress on the snowpack is now behind us, but with that said, it is not possible to quantify the stress vs strength relationship of the facets at the ground.  Large loading events have shown us that there is the potential for massive unsurvivable avalanches to occur.