Turnagain Pass and Girdwood

Problèmes avalancheux

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Possible

  Taille

  1–2

  Recent Avalanches:  On Saturday there were four snowmachine-triggered avalanches and two cornice falls on the backside of Seattle Ridge. No one caught. These were triggered remotely and were 6 to 12" deep. More info here and here. There was also a cornice fall into PMS Bowl on Magnum Ridge (pictured below). Down south in Seward there was a skier-triggered large wind slab avalanche on Mt Alice. The skier was initially caught then able to escape unharmed. We did not hear of any slab avalanches yesterday. Big thanks to everyone for relaying their respective information. 

  Persistent Slab Avalanches:  Despite another calm and warm weather day, triggering a slab avalanche up to a foot deep is still a concern on any slope above 1,500'. The areas most likely to have these avalanches are on the north end of Turnagain Pass (Seattle Creek drainage and Eddies for example) along with the mountains around Girdwood and Portage where more snow fell last week. The problem is a layer of remarkably large buried surface hoar and facets (weak snow that developed during the February dry spell) that is now buried by last week's storm snow. On the north end of the Pass it is around a foot deep. In places on the south end of the Pass that layer averages 6-8" deep and folks have not been triggering avalanches - yet. The other issue is the weak layer is inconsistent. It has been found on some slopes but not others. All this is making for a high degree of uncertainty. Right now the slabs are not too big but when we get more rounds of snow, that will change. 

  It's time to shift our mindset and get used to putting a hand in the snow and looking for this layer. It should be relatively shallow but on slopes that were wind loaded the layer could be up to 2' deep. Watch for cracking and collapsing/whumpfing in the snow. There was a group on Center Ridge yesterday that triggered a large wumpf and subsequent crack on a low angle slope. These avalanches can be triggered remotely (from the side, top, or adjacent too the slope. It is impossible to say what slopes are safe and what are not so if you are not completely comfortable with your slope assessment then sticking to less steep terrain is always the answer. 

  Sun Effect:  The southerly slopes got quite warm yesterday as the sun broke through the clouds. There was also some 'greenhousing' going on making it feel really warm (one of my grad school advisors does a good job at explaining this effect HERE). Lots of rollerballs, 'gloppy' snow, and some wet loose avalanches were reported (photos below). We can guess these aspects are crusted over this morning but should warm enough again today to soften those sun crusts to some degree. If it gets really warm we could see another round of wet loose avalanches and rollerballs again.

  Cornices: There have been multiple reports of cornices falling. These may occur naturally, or they can be triggered from ridgelines. It's a good reminder to give cornices plenty of space as they can break further back than anticipated.

  Glide Avalanches: We're continuing to see glide cracks open and release every now and then. These avalanches are large and unpredictable, so the only way to manage this problem is to avoid spending time under cracks.