Rain crust and NE wind transport on Andesite Ridge

Location Name: 
Andesite Ridge
Region: 
Donner Summit Area
Date and time of observation: 
Tue, 12/15/2015 - 12:55
Location Map: 
United States
39° 21' 1.1808" N, 120° 21' 48.2328" W
See map: Google Maps
US


Red Flags: 
Recent loading by new snow, wind, or rain
Observation made by: Forecaster
Snowpit Observations
More detailed information about the snowpack: 

NE winds have scoured above treeline slopes in this area on NE-E aspects down to the Dec 13 rain crust. Near treeline and below treeline, snow is resisting scouring fairly well. Small pockets of wind slab were note along the ridgetop on SW-W aspects. A party contacted at the trailhead reported triggering a small (size D1) wind slab avalanche at the top of a gully feature on the SW side of Castle Peak in above treeline terrain.

Snowpit tests were performed below treeline on a NE aspect (noted lat/long) on the edge of an avalanche path with a known history of activity in persistent slab conditions. These tests revealed reactive test results along the bottom of the Dec 13 rain crust. This rain crust was located 22 to 30cm below the snow surface at the base of the recent storm snow. ECTP results were repeatable. 2mECT produced a 2mECTN result. No evidence of faceting was observed around the crust. Directly below the crust where snowpack failure was occurring, snow crystal type was identified as decomposing needles.

Photos: Wind scouring down to the Dec 13 rain crust and areas of deposition along the top of Andesite Ridge.

 

Snowpit or crown profile photo or graph: 
Snowpack photos: 
Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
Clear
Air temperature: 
Below Freezing
Wind Speed: 
Moderate
Air temperature trend: 
Static
Wind Direction: 
Northeast
More detailed information about the weather: 

Overall amounts of blowing snow were minor in this area.