Variable Signs of Instability Between Carson Pass and Luther Pass

Location Name: 
Steven's Peak
Region: 
Carson Pass Area
Date and time of observation: 
Fri, 02/17/2012 - 12:00
Location Map: 
United States
38° 43' 40.8" N, 119° 58' 26.4" W
See map: Google Maps
US


Red Flags: 
Rapid warming
Obvious avalanche path
Terrain Trap
Observation made by: Professional Observer
Snowpit Observations
More detailed information about the snowpack: 

Variable conditions encountered between Carson Pass and Luther Pass.

Red Lake Peak NE aspect typical start zones were wind scoured, with unconsolidated non-slab conditions below ridgelines. Pic 1 shows cross loaded area that we avoided today. E aspect above Crater Lake had several loose, wet, natural avalanches that were small and inconsequential. S aspect showed signs of wet instability (pic 2) with fair bonding between old crust and recent snow.

Steven's Peak 1st pitch was windloaded on top of crust/facet/crust combo, but no signs of instability beyond Extended Column Tests (videos, from provided lat/long) observed. 1st Extended Column Test (not filmed) propogated on 3rd tap, resulting in Sudden Collapse below melt freeze crust. Ski cuts of steep test slopes at similar aspect/elevation produced no results. 2nd pitch at 38.739N 19.974W showed much less developed facets, and failed to propogate with 2xECTN results.

Wet snow at surface en route from Stevens to Scott's Lake, and 3-5cm crust on top of cold DFs encountered while climbing E aspect from Hope Valley to Waterhouse summit. Waterhouse to Luther Pass provided excellent travel surface with no crust or slab development observed.

Snowpack photos: 
Any other comments about the observation or links to outside pages that have more info on the observation: 

A 10" thick slab avalanche was observed from a distance along Frog Lake Ridge. This crown line was not seen yesterday close to sunset, and was likely triggered early in the morning today. R3 D1 - unknown trigger, though likely an intentional cornice drop. Appeared to slide above crust layer.

Weather Observations
Blowing Snow: 
No
Cloud Cover: 
25% of the sky covered by clouds
Air temperature: 
Above Freezing
Wind Speed: 
Light
Precipitation: 
None
Air temperature trend: 
Wind Direction: 
East
Accumulation rate: 
None
More detailed information about the weather: 

Winds increased to strong and shifted to W shortly before sunset.