Hatcher Pass

Avalanche problems

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1–2

  Persistent slabs are back on the menu for a short period but expect this problem to transition into a wet slab problem potentially within the week.

  Triggering a persistent slab will be possible above 2500', on southeast through southwest aspects, on slopes 30deg and steeper.  At low elevation, the lack of snow combined with already isothermal conditions will make triggering a slab avalanche unlikely. 

  On Saturday, a human triggered slab avalanche was human triggered on a south facing aspect at 4000'. Although this problem will be hard to find and stubborn in nature today, it will be possible to trigger a slab large enough to bury, injure or kill a person.  In the case of Saturday's avalanche, numerous people skied the slope prior, and set an uphill skin track prior to triggering the avalanche.  The factor that changed that day and today is the intense solar radiation combined with the sun's high angle of incidence and long Spring days, which have added strength and cohesion to the slab and existing snowpack, which is sitting on weak sugary snow and firm faceted crusts. 

  It will be more likely to trigger an avalanche where the snowpack is shallow, which previously slid in the late January avalanche cycle, is 30 degrees and steeper, and on a southerly aspect. 

  The nuance of this problem is while the cohesive slab and persistent weak layer still exist in specific locations today, repeated days with warm temperatures combined with above freezing temperatures for several nights in a row are rapidly transitioning this problem into a WET SLAB problem.  As snow grains melt, they will percolate water through the snowpack, weakening the bond between the slab and underlying weak layer, initiating a wet avalanche cycle. This timing-however-can be hard to nail down, but we are on the trajectory to see this avalanche problem soon. 

  

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1–2

  The snowpack is rapidly changing, even though we have barely passed the spring equinox.  Don't underestimate the power of the sun and long daylight hours. We observed a few new natural wet loose avalanches yesterday, as well as some older sluffs that have increased in size over the last couple of weeks. 

  Wet loose avalanches will be possible to human trigger on southeast through west aspects at all elevations in terrain 40deg and steeper, with an increased likelihood above 3500' in the afternoon. With temperatures expected to RISE into the upper 40s today, expect the snowpack to become unsupportable, punchy, and saturated faster than you can say, "Wait, what..we didn't even have winter, and barely spring." It's true, April feels more like May.  Fortunately, light winds should help keep snow surfaces cooler at upper elevation and ridgeline, at least for the morning. 

  Start of day temps today are significantly warmer than yesterday. Independence Mine is reporting 35F at 5 am and 29F at the same time yesterday. 

  Although it is corn season, it's not going to last for long. On Wednesday, we observed punchy conditions with moist to wet grains on snow surfaces as early as 12pm at 4000'. Today, we are adding WEST aspects to the compass for this problem because of longer daylight hours affecting more terrain. 

  If the snow becomes unsupportable and unstable, seek lower angle terrain. Rollerballs and pinwheels are obvious precursors to wet loose avalanches. 

   The possibility exists for a larger wet loose avalanche to trigger a slab avalanche in specific terrain that previously avalanched in late January.