Fog and rime - wind and slab

• Toured up the “Second Slide” rock outcrop between Shed 10 and Grizzly Gulch.
• Observed windloading (crossloading) in the Second Slide starting zone.
• Continued up the rock-outcrop ridge past Second Slide into the upper starting zone area of Shed 10
• Observed evidence of relatively recent (past week?) avalanche activity on easterly aspects above 7000’ in the Shed 10 avalanche path.
• Descended the Shed 10 path back to the Canyon floor.

Objectives were to:

• • Observe signs of recent avalanche activity.
  • Observe windloading and instability associated with recent windslab formation.
  • Observe snowpack structure and how structure has been affected by recent cold air temperatures and additional loading due to wind and new snowfall.
• Evidence of relatively recent (this past week?) moderate sized (Size 2 or greater) slab avalanche activity on steep and poorly anchored easterly/ southeasterly aspects above 7000 feet elevation.
• Isolated cracking and very small slab activity initiated by skiing throughout today’s tour at all elevations, but particularly above 5500 feet elevation.
• No audible failures and/or collapses observed.

• Wind transport and loading was ACTIVELY occurring on easterly aspects.  This was particularly evident above 5500 feet elevation.
• Approximately 2” to 4” (5cm to 10cm) new snow (HNS) in the past ~24 hours at all elevations in JFS Canyon (Canyon). 
• Observed approximately 25 cm of accumulated snow from this past week.
• New snow from the past week was interfaced with an approximate 3 cm of buried near surface facets which were resting on older snow and/or crust interface.
• New slab formation was cracking in isolated areas during ski cutting and stomping tests (photo). Cracking was not propagating out beyond the localized area where skier weight was being applied. Slab thickness varied between 4” and 10” (10 to 25 cm).

• Cloudy skies and obscured conditions throughout the entire field day.
• Light to moderate snowfall occurred throughout the day with perhaps ~5 cm of new snow (HNS) at Canyon floor elevations in the past 24 hours.
• Moderate wind with strong gusts occurring at elevations above 5500 feet elevation.
• Air temperatures were in the upper-20s to mid-30s (0F) at lower elevations (Below ~5000’) throughout the day and mid 20s (0F) at upper elevations (Above ~6000’). By late afternoon, air temperatures had climbed above freezing at Canyon floor elevations (~4400’).