Turnagain Pass and Girdwood

Problemi valanghivi

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

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

  Probabilità

  Possible

  Dimensione

  1–2

  Recent avalanches: There was a small human-triggered avalanche on the northwest side of Tenderfoot in Summit Lake on Sunday. It occurred on a steep wind loaded slope and failed on a layer of small facets. Fresh debris was observed in one of the chutes off of Goat Mountain in Girdwood, and there were reports of touchy slabs in the alpine terrain on Seattle Ridge.

  We have been discussing the potential for triggering wind slabs over the past few days. This type of avalanche problem often heals within a couple of days. However, due to a weak layer under the wind slabs, we are transitioning from Wind Slab to a Persistent Slab. Like a bad habit that can't be kicked with a New Year's resolution, faceted snow is a weak layer that tends to stick around (persist) and cause problems. Unfortunately, there is a layer of facets (weak, sugary snow) that developed during the December extended cold dry spell. These facets are now buried under the recent snow and in some places, older wind slabs and/or the November raincrust.  Slabs that fail today could be 1 to 2' deep and are most likely found at treeline and above in wind-exposed terrain where the new snow is wind-affected.

  There have been several recent observations of cracking and collapsing, both of which indicate weak snow lurking. Today, be on the lookout for these signs of instability: cracks shooting out from your skis or machine, snow that feels stiffer than the snow below, and collapsing (i.e., whumpfing). Pay attention to wind loading patterns and be suspicious of loaded slopes just below wind-exposed ridgelines, in gully features, and anywhere the snow feels "slabby". Sticking to lower angle terrain with soft snow will be the best way to manage this avalanche problem. 

  Northwest winds today may move additional snow around and continue to build the slabs in the alpine. Watch for blowing snow and changing surface conditions. 

  Dry Loose Avalanches:  In steep terrain protected from the wind, dry loose avalanches could also be a concern today. These could be large enough to bury a person or could carry you over a cliff or into another terrain trap.