Continental

Lawinenprobleme

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  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Likely

  Größe

  1.5–2.5

  Snowfall in mid and upper elevations will continue today. Steady snowfall above 2000 feet has created top-heavy storm slabs that are expected to be sensitive to human triggers.  Areas with stiffer and deeper snow affected by wind will be the most likely to produce an avalanche. Yesterday pockets of wind-drifted snow 1-3 feet deep were found to be sensitive in specific areas in the Thompson pass corridor. Light to moderate accumulations today along with warm temperatures will continue loading a top-heavy storm slab.  

  Coastal mountains near Port Valdez are expected to receive another 12-18 inches of snow at upper elevations today.  Expect to find widespread top-heavy storm slabs in upper elevations. Human-triggered avalanches  2-4 feet deep area likely in upper elevations in these areas. 

  Today it will be important to pay attention to new snowfall amounts in the area you choose to travel, hand shear pits (click link for example) can be a useful tool to quickly gather information on how well the new snowfall has bonded with underlying layers.  This test can also point out weaknesses within the storm snow that are common when the snow is heavier on top (upside down).  Watch for red flags such as shooting cracks and collapsing.  If either of these are present, the snow is clearly telling you that it has enough energy to produce an avalanche on slopes steeper than 30°.

  

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  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  1–2

  Rain is forecasted to begin this morning and continue for several days at sea level to 2000 feet or more. Recently accumulated snow at mid-elevations will become rain-saturated today increasing the Hazard for wet loose avalanches. Lack of new snow accumulation in lower elevations will limit wet loose activity to several inches deep. Areas susceptible to wet loose slides will also have a thinner snowpack with increased rock, brush exposure. 

   The potential size of wet loose slides is directly correlated to the depth of wet snow and the vertical relief and shape of the slope(does the slope fan out? or does it funnel? Is the wet snow shallow? or Deep?).  The consequences of wet loose activity can be compounded by terrain traps or cliffs.  Dragging a pole basket through the surface of the snow downward on a slope can give you an idea of how much entrainment potential the surface snow has (does it drag straight through? or does it collect snow and spread out as you drag the basket?).  The more entrainment that happens the greater the potential for wet loose to occur in terrain steeper than 35°.

  This problem is expected to grow in depth and distribution as rain is expected to continue through the weekend and become heavier.

   

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  Deep Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Unlikely

  Größe

  2.5–3.5

   Our snowpack has undergone a major change since the beginning of January.  What began the month as a fairly thin snowpack with very thick vegetation below the brushline has transformed to a thick midwinter snowpack with the alders being mostly buried above 2000'.  Below 2000' the snowpack remains thin.

  This transition is a very welcome sight but it has put significant stress on our snowpack, especially during times of heavy precipitation.  On the 11-12th we received 100" of snow on Thompson Pass in a 48 hour period.  This caused a significant natural avalanche cycle that failed at weak layers in the mid snowpack.  As the new snow was allowed to settle a much stronger snowpack was observed the following week.  Again on the 19th we received a significant snowfall event with 30" on Thompson Pass in 24 hours.  This produced a few large avalanches (see avalanche tab below bottom line) but was much less significant in distribution than the previous cycle.  

  Triggering a deep slab avalanche remains unlikely today, however expect for the likelihood to increase this weekend as heavy precipitation is expected.