Turnagain Pass

It is now been over 10 days since the November 16th surface hoar layer was buried and it remains reactive and our primary layer of concern. Yesterday skiers reported triggering small slides in Main Bowl (Seattle Ridge) on the buried surface hoar layer in steeper terrain (40 degrees). One skied off of the slab and the other was carried but stayed on top. It is important to remember that this widespread layer of buried surface hoar is sitting below 1-2 feet of snow and that observers keep finding this layer on all aspects and elevations throughout Turnagain Pass. Stability tests also continue to show that is slab/weak layer combination has the potential to avalanche. Up until a few days ago human triggered (including remote triggered) avalanches were happening daily with a couple dozen avalanches reported over a 7-day period. These avalanches have been small to medium in size; just large enough to bury a person or seriously injure you in a ride. Larger and/or steeper, more wind-loaded slopes that haven’t been ridden still have the potential to avalanche and could fracture once onto the slope. Be aware of the consequences below you and keep an eye out for recent wind loading, shooting cracks and whumphing sounds (RED FLAGS).  Practice safe travel techniques like regrouping in safe zones and only expose one person at a time in avalanche terrain. This can be challenging to practice in crowded areas, thus be extra aware of other groups who may be traveling above or below you. Don’t forget buried surface hoar is a persistent weak layer and human triggered avalanche are still possible. This layer has not gone away and should be a major factor in slope choice today.

Skier triggered slides in Main Bowl, Photo: Eric Dahl

Shovel Tilt Test showing the slab over the buried surface hoar from pit near Hippy Bowl. 

The snow that fell Saturday night was light and fluffy and will easily be transported with moderate winds. Early this morning there was a few hours where the winds picked up on Seattle Ridge gusting to 30 mph. The Sunburst weather station is down so it’s hard to determine if this was the same across the Pass. There was some increase in wind speeds at road level as well. It will be important to watch for signs of recent wind loading and if the snow feels stiffer underfoot. Look for shooting cracks. Triggering a small wind slab is possible in steep leeward terrain near ridgetops. This wind loading may add stress onto the buried surface hoar layer. Pay attention to changing conditions and choose terrain carefully. 

Several glide avalanches have released this week including one observed Saturday morning on the West face of Pyramid. Several glide cracks have been noted in popular terrain like Tincan’s Common bowl and the SW face of Sunburst. If you see glide cracks give these a wide berth, minimize time spent underneath, and remember these are totally unpredictable. They are not triggered by humans and are the entire snowpack releasing. In places like Tincan Common this could be over 4′ of snow.