Avalanche: Ogden

Observer Name
Powder Mtn Snow Safety (Everett & Hamlin)
Observation Date
Sunday, March 31, 2019
Avalanche Date
Saturday, March 30, 2019
Region
Ogden
Location Name or Route
Scrapies, North End of James Peak Ridgeline Outside of the Powder Mtn Area Boundary.
Elevation
9,200'
Aspect
East
Slope Angle
45°
Trigger
Snowboarder
Trigger: additional info
Unintentionally Triggered
Avalanche Type
Hard Slab
Avalanche Problem
New Snow
Weak Layer
New Snow/Old Snow Interface
Depth
12"
Width
300'
Vertical
1,250'
Caught
1
Carried
1
Comments
On Saturday the 30th around 1300 a single snowboarder in a group of 4 had a close call, when he exited our terrain via the James Peak ridge line and into uncontrolled backcountry terrain. This slide path is named "Scrapies" for its otherwise flat rocky outcrops and narrow chokes in 2 separate chutes. This slide path is a regular producer and typically runs a natural cycle with even small amounts of new snow and south west winds due to large fetch zones. Avalanche classes of R1-2 and D1-2 are regular and typical December-February, with R2-3 and D2-3 usually occurring late in the season with higher annual snow totals and bridging of rocky anchors. Spring time regularly brings high incidents melt freeze and wet loose activity and incidents like this.
This incident was classified as a SS-ARu-R2-D2-I; 30 cm crown, 250-300’ wide, running 1000-1250 vertical feet; the starting zone is skiers right of center @9200', E aspect, 45-degree slope. The snowboarder was carried approximately 600 vertical feet, over several large rock outcrops before being able to stand up and exit the path skier's right back into the area boundary. Fortunately, we were able to contact the triggering party soon after it was observed and confirmed that there were no injuries or burials.
Based upon our investigation on the right flank adjacent to the starting zone, we found that the avalanche comprised of new snow from storm #33 in the form of a well-connected slab. This slab which likely rode on a slick bed surface comprised of melt freeze forms, and a buried NSF layer. This layer was very small and difficult to identify in grain identification, but was very noticeable with a brush to the pit wall (it is possible that the layer was simply a density interface from the onset of storm #33). An Extended Column Test ECT was performed and initial movement in the slab was noted at tap #7-8 with the column failing on tap #14, it broke with a classic “Pop” & “Drop”. The deposition zone was nearly 1000’ long and ranged from 6” to 3’ deep at the toe, it should be noted that gouging and wet loose type debris were found in the deposition.
***Note*** Powder Mountain and this terrain is located on private property, we limit access to this terrain and many other areas with a Closed Area Boundary Policy. Over the past several seasons we have encountered several incidents in areas adjacent to our area boundary that affect SR 158 (Powder Mountain Hwy) and this terrain accessed via James Peak.
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