Summit Lake

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  1–2

  Overnight winds gusting 60 mph and strong southeast winds (20 to 40 mph) expected today will continue to blow snow into touchy wind slabs around 1’ deep. These will be easy to trigger on wind loaded slopes and have the potential to step down to a weak layer deeper in the snowpack creating an even larger avalanche. The intensity of the wind will create wind slabs in upper elevations and mid elevations. 

  Recent avalanches and blowing snow are the biggest red flags telling you wind slabs are forming or releasing. Stiff snow or shooting cracks underneath you are clues you are traveling on a wind slab. These tend to form below ridges, on convex rollovers and in loaded gullies. The worst case scenario is that triggering a wind slab avalanche may create a much larger avalanche that releases on deeper layers.

• 

  Wet Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  2–3

  Recent Avalanches: There has been an ongoing wet avalanche cycle over the past few days. Glide avalanches and wet slab avalanches have been releasing in Turnagain Pass, Girdwood Valley, Summit Lake, and near Lost Lake. Some have been very large running to valley bottoms. 

  As the storm continues to pummel the peninsula Summit Lake may receive another 2 to 4” of snow on an already dangerous snowpack. Warm temperatures have allowed liquid water to move into the snow where it tends to run like a creek down weak layers resulting in large wet avalanches. This storm will increase the amount of water in the snow also making it heavy. Because of this there is a chance of large wet loose and wet slab avalanches. These could happen on all aspects and will be large enough to run into valley bottoms. Glide avalanche activity is also expected to continue as the storm adds water to the snowpack. 

  All of this means that we need to take a different approach to travelling in the mountains this weekend. This is a challenging situation where many hazards could have severe consequences. We recommend avoiding traveling under runout zones. The safest option would be to avoid traveling in or under avalanche terrain until the storm subsides.  

  Storm totals below are from Thursday morning to Saturday morning:

  • Portage and Whitter: 25 to 30+” snow (5.38” Snow Water Equivalent (SWE)
  • Girdwood: 8 to 12" snow (1.04” SWE)
  • Turnagain Pass: 6 to 10" snow (0.8" SWE)
  • Summit Lake: 1 to 2" snow (0.1" SWE)
  • Seward/Lost Lake: 0.9" SWE from the Exit Glacier SNOTEL site. 1 to 2” snow at Primrose weather station (0.1" SWE)

  

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1–2.5

  This will be the largest storm to add stress to a layer of surface hoar buried 1 to 2’ deep. We are not sure if it will be enough to trigger natural avalanches. Where the layer exists we feel it may be easy for a human to trigger. This layer has been found between 2000’ and 3,500’ in areas sheltered from the wind. Because these layers may be more reactive and potentially release naturally the safest option is to avoid traveling on or below steep slopes and run out zones.