Seeley Lake

Problemi valanghivi

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta quota
  • Limite del bosco
  • Sotto il limite del bosco

  Probabilità

  Likely

  Dimensione

  1–2

  There are two primary buried layers of concern making up our persistent slab problem. The most reactive and concerning is surface hoar that was buried and preserved on February 14th. This layer is worst at upper elevation on northerly or shaded slopes where human triggered avalanches are likely.  At mid elevation and on south aspects, the layer is present but less continuous and less reactive but still possible to trigger an avalanche on.  The second layer of concern is a lower layer of buried surface hoar and near surface facets from late January. This layer is showing less reactive, but still is not trustworthy.  

  Another factor affecting the avalanche problem is slab thickness and density. You are more likely to trigger an avalanche in areas with a thicker or harder slab like wind drifted terrain where a larger slab is present. Don't ignore areas with a thinner slab though, as they are still capable of avalanching. 

  This is a tricky problem because in 75%  of the affected terrain, it is behaving like a moderate danger problem where human triggered avalanches are possible. In the other 25% of the terrain, triggering an avalanche is very likely. Some common traits of the most dangerous terrain are northwest-north-east aspets between 6500 and 8000'. 

  Here is an example of a human triggered avalanche on this layer. Check out the observation page for a full list of recent avalanches and unstable snowpack observations. 

  You may not see obvious red flags like cracking, collapsing or whumfing before triggering an avalanche. To identify the problems, dig in the snow. Buried surface hoar will present as a thin grey line running across the snowpit wall. Dig quick pits in multiple locations as surface hoar is highly spatially variable. 

  If you find buried surface hoar, do not trust it. Surface hoar is an especially nasty buried weak layer and can produce avalanches on low angle slopes down to 30 degrees in slope angle. 

  

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta quota
  • Limite del bosco
  • Sotto il limite del bosco

  Probabilità

  Possible

  Dimensione

  1–1.5

  Observations the past few days have shown blowing snow and small wind slab formation. Overnight and into today, winds will continue building wind slab along ridgelines. These slabs are small, and unlikely to produce an avalanche large enough to bury you, but they still pose a risk for two reasons. The first is that even small avalanches can be dangerous if they carry you into trees, over rock bands, or into other terrain traps. Second, small wind slabs have the potentail to step down and trigger larger and more destructive persistent slab avalanches. 

  Unfortunatly, our primary wind station has not been reporting reliably since yesterday morning and exact wind speeds and direction are uncertain. Identify wind slabs by their smooth and rounded appearance. If you see shooting cracks around your skis or fresh avalanches, avoid slopes over 30 degrees in slope angle. 

  

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta quota
  • Limite del bosco
  • Sotto il limite del bosco

  Probabilità

  Possible

  Dimensione

  1–1.5

  Temperatures are expected to warm to 40 at upper elevation and 50 at mid and lower elevation today. If combined with some sun, it will be possible for the snow to get wet enough to produce wet loose avalanches. If you find yourself sinking into wet and unsupportable snow, or see rollerballs begin to fan out into loose snow avalanches, it is time to exit avalanche terrain or move to a shadier/cooler aspect.