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

  Likely

  Dimensione

  2–3

  Recent avalanches: We got reports of a snowmachine-triggered avalanche lower down in Warm-Up Bowl on Seattle Ridge last Thursday (1/22) that looks like it released on the December Facet layer. There was also a notable, large remote-triggered avalanche on Sunburst last Wednesday (1/21) on this weak layer, which wiped out several sets of recent ski tracks. 

  The intensity of the current storm system is expected to ratchet up today, with 4 to 6" of new snow expected in Turnagain Pass and Summit Lake and 6 to 12" in Girdwood, Portage, and Seward. Stronger southeast winds will accompany the heavier snowfall, averaging 20 to 30 mph with gusts up to 45 mph. This gradual accumulation of new snow and wind is likely to be enough to make our weak layer, which is buried 2 to 4' deep, more sensitive to human-triggered avalanches and could cause some natural avalanches in specific areas that receive higher snowfall totals or heavier wind loading. 

  While the likelihood of triggering an avalanche today is on the rise, the advice for how to deal with the problem stays the same. You can use conservative terrain selection to control your risk exposure by sticking to simple, low-angle terrain and avoiding the runout zones of overhead avalanche paths. Remotely triggered avalanches have been especially common on this weak layer, which means you could trigger an avalanche from low-angle terrain onto connected steeper terrain. 

  

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

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

  Probabilità

  Likely

  Dimensione

  1–2

  With yesterday's 2" of new snow (0.2" water), combined with another 4-12"  of new snow today (0.25 to 1" of water), there will be plenty of soft snow on the surface to be transported into fresh wind slabs. When the winds pick up this afternoon, wind slabs up to 1' deep will be forming on leeward slopes. You can test for wind slabs by using small test slopes to look for shooting cracks or small avalanches in wind-loaded pockets of terrain. These typically form near ridgelines, gullies, and convex rolls where wind-transported snow tends to accumulate. 

  Storm Slabs: In areas like Girdwood, Portage, and Seward, where snow totals are expected to be on the higher side today, there is a chance of triggering an avalanche at the interface of the new snow and the old snow surface, even in sheltered terrain. Using small test slopes or hand pits can be a good way to check how well the new snow is sticking to the old snow surface. This type of avalanche is much smaller than our main concern in problem 1, but it can still get you in trouble if there is a terrain trap involved.