Summit Lake

Problemi valanghivi

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

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

  Probabilità

  Likely

  Dimensione

  2–3

  Winds quieted down and precipitation slowed overnight as yesterday's storm moved out. Although a few inches of snow may fall today with southerly winds 10-20mph, it will be the rapid loading of snow and windblown snow during the past 30 hours that is creating our most concerning avalanche conditions. Since Saturday afternoon, the Girdwood and Turnagain Pass mountains saw 2 to 3+' of new snow above 1,500' while Summit Lake had closer to 1.5 to 2' (this is on top of the 2' that fell Friday night/Saturday morning). The rain/snow line was actually lower than forecast (yay!), fluctuating between 300 and 1,500'. Ridgetop winds were easterly averaging an impressive 60-90 mph with what I believe ties Sunburst's all-time record gust of 132 mph. 

  Weekend storm totals, since Friday evening:

  • Girdwood: 4.7" Snow Water Equivalent (SWE), equaling 4-5' snow above 2000'.
  • Turnagain Pass: 5.6" SWE equaling 4-5' snow above 2000'.
  • Summit Lake: 2.3" SWE equalling 2-2.5' snow above 2000'.
  • Lost Lake: 6.1" SWE equalling 5-6+' snow above 2,000'.

  Recent Avalanches:  We can assume there were countless natural avalanches yesterday in the forms of storm slabs, wind slabs, cornice falls, and loose snow avalanches. How large these were are yet to be seen. Hopefully we'll get some eyes on the slopes today if skies clear enough.

  Storm Slabs:  If there are any slopes that didn't see wind effect, then they could still be harboring unstable storm slabs. These are slabs composed of the newest layer of storm snow and could be anywhere from 1-2' deep depending on location. Snowfall rates yesterday were up to 2" per hour at times at Summit Lake. The good news is this type of avalanche issue typically heals in a couple days, but today we are well within the danger zone. 

  Wind Slabs:  With such extreme winds, we can expect to find wind slabs on most slopes above treeline and any exposed areas in the trees. Wind slabs could be many feet deep and extend across slopes. Strong winds also have a way to create wind slabs in mid elevations, on rollovers, in gullies, and lower on slopes. 

  Cornices:  Along ridgelines, cornices should be larger and could be close to failure. Give these an extra wide berth as they are notorious for breaking farther back than expected. They also could trigger a slab avalanche below if one does fall.

  Travel Advice:  Today is one of those days to seek out sheltered lower angle terrain while the steeper slopes adjust to the new load. Keep a lookout for signs of recent avalanches and where winds have loaded slopes. If you start to see any cracking in the snow under you or collapsing/whumpfing in the snowpack, then you will likely trigger an avalanche if the slope is steep enough.

  

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

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

  Probabilità

  Likely

  Dimensione

  2.5–3.5

  There are several weak layers in the Summit Lake area that are now buried under 3 to 4' of new snow from the past week. These are various layers of facets and buried surface hoar, along with weak snow near the ground. Any one of these layers is suspect currently. They were the cause of several large avalanches when they were first buried on January 6th.  They have now been overloaded by 2 more feet of snow and until skies clear, we won't know if they produced more big avalanches or not. I'm betting they did. 

  Not only is it possible a person could trigger a large avalanche breaking in these layers, but it's also possible that a wind slab or some other form of storm snow avalanche or cornice fall could cause these weak layers to fail. In this case, an avalanche up to 5' deep could result that spans an entire face. This is just another reason to let the mountains rest after the storm.