Turnagain Pass

New snow and wind have combined to create very unstable slabs 1-3’ range.  Ridgetop winds from the East (SE to NE) have picked up into the 40’s and 50’s mph overnight with serval gusts in the 90’s at Sunburst weather station last night. An additional 10-12” of snow is forecasted for the higher elevations today and will increase the size of these slabs. These slabs will release naturally in steep terrain and could step down into older layers in some locations. Natural avalanches could run the full length of a slope, thus it will be extra important to avoid being near any runout zones today. Avoid places like Johnson Pass where an avalanche could cross the trail. Rapid loading due to heavy snow and strong winds will continue through late morning. Gusty winds are expected through early evening as precipitation dimishes by early afternoon – these winds will make natural avalanche activity likely throughout the day. 

This is not a complicated situation.  Avoidance of avalanche terrain is the only way to “manage” this problem today. 

Photo of W facing slopes of Eddies following a wind event on Monday into Tuesday that loaded SW aspects. SW aspects will be more loaded today and it will be important to keep your distance from the runout of slopes steeper than 30 degrees.  Photo by Mike Ausman 

A variety of weak snow (facets and buried surface hoar) that sit near the ground or mid-pack remain the most concerning layers today. Avalanches occurring in the upper layers have the potential to step down and release the entire snowpack in some places. Girdwood Valley and Johnson Pass area have more potential for this to occur where a generally thinner and weaker snowpack exist. In cases where this happens, the volume will be large, could run long distances and potential for burial, if caught, is high.  Avalanches occurring at this layer have a high propagation potential, which means that fractures can and will travel across slopes. 

Because of this travel in avalanche terrain is not recommended today including being in the run-out of a steep slope.  Since this problem exists at all elevations, it will be important to avoid the runout of terrain from above when traveling in the flats like in the flats below Seattle Ridge. 

An Eastern facing bowl on Raddedtop that released to the ground sometime on Monday during a period with strong winds and snowfall. This is a good example of a thin snowpack in parts of the Girdwood Valley. The debris from this avalanche was is estimated to have run about 1000′.

Rain falling on snow to 1,000’ will weaken the surface snow and possibly an older layer beneath. Wet loose avalanches are likely and wet slab avalanches are possible due to a layer of buried surface hoar 1-2’ below the surface. In channeled terrain an avalanche from above will likely entrain weak snow in the lower elevations increasing overall volume. Don’t under estimate small terrain features with high consequences. Triggering a wet slab in the lower elevations of Twenty mile or Placer could have high consequences if pushed into or over terrain traps such as cliffs, gullies, or trees. Again it will be important to avoid steep terrain and maintain a conservative distance from all run-out zones.