Ralston Peak

I triggerred a small wind slab avalanche at about 8500 feet on a NE aspect on Ralston Peak in the bowl above Ralston Lake.  I would like to say it was intentionally triggered, but it was not.  I would classify it as AS-HS-D1-R2.  It ran about 50 vertical feet and was probably 150ft wide. The crown was 4-6" max.  It broke above me at a classic convexity in the slope and quickly shattered about 100 ft in both directions.  I was caught up for just a second but quickly realized that it would be small and harmlesss.  The snow fanned out onto a gradual bench, and deposition was about 1-2ft deep.   Due to the super flat light, the position of the rest of my group on the slope, and the possibilty of remaining hazard in this somewhat complex zone, I did not get any goood pictures, and was not able to investigate much more.

If you did see the pictures, you would probablly think it was hardly worth reporting, but it was interesting for a couple reasons.  First, I was surprised.  We had no real signs of instabilty throughout the tour except for some small loose wet instabilities. There was some blowing snow, but we skied our fist pitch in off of the ridgline where loading was the most intense and had no results or concerns.  Stability has been good, and the wind has had minimal impact on the hazard as of late. The second point of interest is that if I did have the chance to investigate further, I would bet that this shallow wind slab failed on barely buried surface hoar or NSF.   Being mid slope BTL and a fairly protected N facing convexity, it would have been an ideal place for the surface hoar to form and persist, and then get buried by the inch or two that fell in the last four days or so.  Then the wind blew some snow around and stiffened up the slab.  The fracture character - breaking above me and shatterring out a long ways relative to the path in both directions is also consistent with my experience with buried surface hoar.  

Overall, a relatively harmless incident, but it did change our ski plans for the remainder of the day.  We had a informal debrief amongst the group, and I felt it was interesting and valuable to share.