Salt Lake

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  2

  Wind loading from a new direction will present the backcountry traveler with scattered drifts on nearly all aspects at the mid and particularly upper elevations. The new drifts - like yesterday's - will still be sensitive and based upon weak layer crystal type - may be triggered from a distance. These are soft slabs up to 12-18" deep and tend to respond well to ski cuts and cornice drops when they are predictable and obvious. If they can still be triggered remotely (at a distance), all bets are off. Approach steep wind drifted terrain with caution.

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  3

  There are two persistent weak layers of concern.

  1. Weak surface snow and patches of surface hoar buried Saturday night. This layering has likely been the culprit in at least four avalanches from Murdock Peak east to 10,420' along upper Mill Creek to BCC. These have been 1-3' deep on wind drifted north to northeast facing slopes with elevations from 8800' to 10,200'. Some of these have run naturally, some of been triggered at a distance. Cracking/collapsing are key indicators here; snow pit tests should also be reliable indicators for intended terrain - look for the 'thin grey line' a couple feet down in the snowpack (pic below). Caution should be observed as these may be triggered on approach or from below.

  2. Enough snow and wind have tipped the balance in some areas to produce avalanches down near the ground 3-6' deep. These will be much more prominent in terrain that has avalanched previously this winter and may require more of a significant trigger to snap the rubber band. The large slides along the Park City ridgeline on Tuesday, and the Little Water Peak slide on Monday (observation) highlight this problem. These slides were triggered from cornice falls and were on steep, wind-loaded slopes facing northeast. Tuesday's natural from South Monitor highlights how large these avalanches can be. (pc: Mark White). In contrast to the more shallowly buried weak layers, cracking and collapsing are unlikely to be present and snow tests may be highly variable. These are lower-probability high consequence. Photo from control work yesterday. One large large collapse was noted on an east facing aspect at 8400'. Not a good sign.

  It's a touch outdated, but looking at the Avalanche Problem Toolbox will also provide good details and travel advice on these two types of avalanches (previously Persistent Slab and Deep Slab) .

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1

  Point of Fact: I expect both dry and wet sluffing today in the most recent low density snow. Each are predictable and more easily managed but complacency leads to accidents.

  Loose Dry: Lower density cold smoke will sluff with provocation and perhaps naturally on the steepest terrain of all aspects. Loose dry snow avalanches can pack quite the punch and entrain lots of snow in steep, sustained and enclosed terrain (couloirs and gullies). Ski cuts are effective but it's key to continue from area of safety to area of safety, moving across the slope.

  Loose Wet: despite sub-freezing temperatures, the warming temperatures and direct sun will dampen and destabilize the recent low density snow on the steepest sunlit slopes. Keep an eye out for rollerballs and dampening snow and avoid steep southerly terrain by midday/afternoon.

  It's a touch outdated, but looking at the Avalanche Problem Toolbox will also provide good details and travel advice on these two types of avalanches (previously Loose Wet and Loose Dry) .