Continental

Lawinenprobleme

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  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Likely

  Größe

  1–2

  As of 6 am, 10 inches of new snow was recorded in Valdez that was wet and heavy due to rain overnight.  Most valley locations are showing temperatures near or above freezing temperatures.   Moderate to heavy snow is expected to continue, with a mix of rain at lower elevations.  An additional 6-12+ inches is forecasted over the next 24 hours with the freezing line expected to return to sea level by Sunday morning, winds have been moderate from the SE and are expected to increase in strength through the day.

  Storm slabs that are currently forming are expected to be reactive to human triggers today 1-2 feet in depth as increasing temperatures overnight have formed a top heavy cohesive slab.  Moderate SE winds will have created deeper more sensitive pockets on the lee side of ridges, terrain features, and cross loaded gullies.  Avalanches that involve storm snow will have the potential to step down beneath old wind slabs in isolated locations creating larger/ more destructive avalanches (see problem 3).

   In most locations, we now have all three ingredients for the avalanche recipe.  We have a smooth bed surface from the outflow winds at the beginning of the month.  A potential weak layer formed in many locations as the 3-6 inches of snow from the 3rd-4th became faceted at the surface during the clear and cold weather of Feb 6th-8.  Lastly and most importantly, we have a slab forming.

  Pay attention to the amount of new snow that has accumulated and the degree of wind redistribution in the area you choose to travel.  Use hand shear tests and small test slopes to determine sensitivity while watching for red flags such as cracking, collapsing, and avalanche activity.  Maintain good communication in your group, and identify conservative travel routes and potential hazards that may exist.  The hazard will slowly be on the increase through the day with additional snowfall accumulation.

  

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  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Likely

  Größe

  1–2

  Overnight temperatures have risen to near or above freezing for valley locations.  Rain on snow has occurred below 1000' , creating the potential for wet loose activity.  The size of natural or human triggered activity will depend upon the vertical relief of the slope and its steepness.  Wet loose activity can be hazardous to users because even small slides have the potential to knock you off your feet.  Avoid steep terrain and terrain traps at low elevations.  

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  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  2–3

  Old wind slabs that formed at the beginning of the month have recently shown signs of instability in small isolated pockets.  This is due to these slabs being deposited on a deep upside down storm slab from 1/28-29 and a decomposing rain crust at low elevations south of Thompson Pass.  As storm slabs have settled and wind slabs gained strength signs of instability have decreased although they could remain a concern in steep terrain in small isolated pockets.  Thinner wind slabs (less than 1 foot) have been where instability has been observed.  

  This potential avalanche problem will be put under additional stress with new snowfall and rising temperatures.  Step down avalanches are possible.  New snow has made visual identification of this problem no longer possible.  pole probing can identify what the bed surface consists of.  Areas where you can pole probe beneath old wind slabs  may remain a concern in steep terrain.  

  This storm will be a good test as to whether this avalanche problem is still a player