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

  Multiple skier triggered avalanches were reported yesterday on the north side of Thompson Pass that involved the most recent new snow. These were in the 1 foot range and were likely attributed to areas that were loaded by the strong south-southeast winds that were occurring yesterday.  Additional overnight snowfall will add depth and stress to the already touchy storm slabs that were reported yesterday.  Human triggered avalanches will be likely today at upper elevations up to 2 feet in depth in wind loaded areas and possible at mid elevations.  Sugarloaf snotel at 500' picked up 6 inches of snow overnight, Thompson Pass reported 4.  Expect new snowfall totals to exceed 1 foot at upper elevations with wind loaded pockets up to 2 feet in depth likely.  Snowfall amounts are expected to be higher near the coast.

  Today it will be important to pay attention to new snowfall amounts and the amount of wind redistribution that has occurred within this new snow.   Winds were predominantly from the SE, however, expect variation in wind direction dependent upon terrain influence.  Use hand shear pits, test slopes, and terrain progression as tools to assess the sensitivity of the new snow.  Expect steep wind loaded terrain to be the most likely area to trigger an avalanche today.  If you experience signs of instability such as shooting cracks, collapsing or avalanche activity assume that unstable snow exists in your area.

  Storm slab avalanches may be able to step down to weak snow buried ~3 feet deep (see problem 3) and create much larger avalanches.

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  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Likely

  Größe

  1–2

  Wet loose avalanche activity will be likely today.  Fresh snow that has fallen over the last few days will be shedding off steep solar aspects during the heat of the day.  Plan your route to avoid exposure to slopes when they are the most prone.  Expect all aspects to be affected at low elevations today.  At mid to upper elevations wet loose activity will be limited to the southern half of the compass.

  Wet loose conditions are easy to identify.  Once more than a few inches of snow becomes moist-wet (you can easily form a snowball) then wet loose avalanches will become possible both human triggered and natural on steep terrain.   Different aspects will experience peak hazard at different times of day.  East aspects are the first to warm up, then South and finally West.  Low elevation slopes that are perpendicular to the sun will be the most prone to wet loose activity, however wet loose activity is expected to extend into the upper elevations today on solar aspects.  Roller balls and snow snails are a good visual indicator that wet loose is currently an issue.  

  Avoid travelling on or below steep terrain where more than a few inches of moist snow exists.

  

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  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  2.5–3

   A persistent weak layer consisting of buried surface hoar 2-3 feet beneath the surface exists in our snowpack above 3000'.  This layer has not been observed or reported to be reactive along the road corridor near Thompson Pass in the most commonly used areas.  Large human triggered avalanches have occurred in more protected areas beyond the road corridor where higher snowfall totals have occurred, and the layer in question likely formed more substantially and was buried more intact.  The last avalanche activity reported at this layer occurred on 3/2 with one instance involving a D2-2.5 avalanche that caught and carried a skier causing him to pull his airbag and lose some gear.  It is very likely that other avalanches have been triggered at this layer since and have not been reported.

  This layer has been observed in multiple locations above 3000' and has been observed to be rounding (gaining strength) and also mixed with other grains.   This is positive progress, however, we need to keep in mind that incremental loading of this layer can increase its sensitivity.  Storm slab avalanches may have enough force to step down to this weak layer.  Assesment of this layer will be challenging as it can be difficult to locate and ECT tests will be less effective as this layer becomes deeper with continued snowfall accumulation.  Propagation Saw Tests will be a more effective tool to test this layer.