Turnagain Pass and Girdwood

Problemi valanghivi

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

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

  Probabilità

  Very Likely

  Dimensione

  1–2

  Recent avalanches: The most recent storm system started on Sunday night, and we have no information about avalanche activity so far due to low visibility. After the last storm on Thursday, most avalanches we have observed appear to have released at the interface with the new storm snow, but there were a few with wider propagation, like on Pastoral and Seattle Ridge, that may have released on the December facet layer. 

  Our current warm and wet storm has been favoring areas near the coast with heavier precipitation. Girdwood has received 0.7" of water in the past 24 hours (6 to 10" of new snow above 2500'), and Portage has received 2.4" of water (24 to 30" new snow above 2500'). Heavy precipitation will continue throughout the day, with another 0.5 to 1.0" of water expected in Girdwood and Turnagain Pass and closer to 2.0" of water near Portage and Placer. That amounts to an additional 6" to 2' of new snow today above 2500', with coastal areas being heavily favored. Strong east winds averaging 40 to 50 mph will accompany the precipitation. 

  The mix of rain and snow in this storm is causing a variety of potential avalanche problems depending on elevation. Below 2500', the rain will saturate the snow surface and could cause natural or human-triggered wet loose avalanches on steep slopes. The added weight of the rain could cause avalanches on our buried weak layers as well, see problem 2 for more details.  Above 2500', the strong east winds and new snow will make natural and human-triggered wind slab or storm slab avalanches very likely. Wind slabs could be up to 2' deep and are most commonly found along ridgelines and convex terrain features. In sheltered terrain, avalanches at the interface of the new snow and the old snow surface about 1' deep are also possible. 

  Given the nasty weather and potential for natural avalanches, we recommend avoiding avalanche terrain today and sticking to low-angle slopes if you brave the elements. Areas receiving heavier precipitation, like Girdwood and Portage, are most likely to see natural avalanches. If the precipitation remains light in Turnagain Pass, then human-triggered avalanches in wind-loaded areas will be the main concern. 

  

• 

  Deep Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

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

  Probabilità

  Possible

  Dimensione

  2–3

  The added weight of the current storm will make very large avalanches on the December Facet layer, which is now buried 2 to 5' deep, more likely today. Our recent field observations have shown that this weak layer is slowly gaining strength as it gets buried more deeply. This is an encouraging sign for the long run, but during active loading events like today's storm, there is a chance we could see natural or human-triggered avalanches on this layer. These are most likely to be triggered from a thin spot in the snowpack where it is easier to initiate a failure in the buried weak layer. To avoid this issue, you can follow the same travel advice as problem 1, which is to avoid steep slopes and runout zones of overhead avalanche paths during this heavy storm.