Seward and Lost Lake

Problemi valanghivi

• 

  Wet Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

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

  Probabilità

  Likely

  Dimensione

  2–3

  Recent Avalanches: Glide avalanches, wet loose, and wet slab avalanches have been releasing in Turnagain Pass, Girdwood Valley, Summit Lake, and near Lost Lake for the past week. Some have been very large running to valley bottoms. 

  The next round of active weather is arriving this morning, and we are expecting avalanche conditions to remain dangerous today. Although precipitation rates are expected to be a bit lighter than what we saw earlier this weekend, this system continues to add weight and water to the snowpack. We are now seeing snow at sea level, but the snowpack has not been able to refreeze since early last week. Water has been impacting weak layers buried earlier this season - including the 2/14 buried surface hoar layer discussed in Problem 2 - which increases the chances of seeing big avalanches failing deeper in the snowpack.

  Wet avalanches remain the biggest concern for now. This includes wet loose, wet slab, and glide avalanches. These will be most likely at and below treeline, and they may run into lower elevation runout zones. The best way to manage the current dangerous avalanche conditions is to avoid traveling on or below steep terrain.

  Storm totals below are from 12 AM Friday morning through 6 am this morning:

  • Portage: 8.7" Snow Water Equivalent (SWE), equaling 4 to 6' snow above treeline.
  • Girdwood: 3.2" SWE equaling 1.5 to 2.5' snow.
  • Turnagain Pass: 1.9" SWE equaling 12-18" snow.
  • Summit Lake: 0.3" SWE equaling 1-3" snow.
  • Seward/Lost Lake: 1.9" SWE equaling 12-18" snow.

  Cornice Fall: These last few days of wet and windy weather will be pushing cornices to their breaking point. These may fail naturally, and they may trigger larger avalanches when they land on a slope. Avoid spending time below cornices, and give them plenty of room if you are traveling along ridgelines.

  

• 

  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

  This extended loading event is still adding more stress to the layer of surface hoar that was buried on 2/14 and remains a concern today. As mentioned above, this layer has likely been impacted by liquid water at and below around 2500', but that is not the only concern. At upper elevations the weight of this new snow is pushing this layer closer to its breaking point. The layer is now 1 to 4' deep on average, and has the potential to make a very large avalanche.

  This will be difficult to assess. We had been seeing conflicting test results on this layer prior to this most recent storm, and in some cases we found stable test results on slopes that produced avalanches later. Because of the high uncertainty and the severe consequences of triggering an avalanche, the safest way to manage this problem is to avoid traveling on or below steep terrain.

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

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

  Probabilità

  Likely

  Dimensione

  1–2.5

  We're finally seeing the snow line drop today, with snow to sea level at the Whittier Tunnel this morning. This will make for new snow avalanche concerns, especially at mid and upper elevations which have been receiving snow all weekend. This includes storm slabs, which may be a foot deep or deeper above 2500'; wind slabs up to 2' deep or deeper, and dry loose avalanches. Some of these avalanches may be small, but as the snow and wind continues these are getting large enough to have serious consequences. Combined with the two other avalanche problems discussed above, the safest bet today will be to avoid traveling on or below steep terrain.