Observations from Carson Pass

Location Name: 
Frog Lake Ridge
Region: 
Carson Pass Area
Date and time of observation: 
Tue, 04/20/2010 - 18:30
Location Map: 
United States
38° 40' 50.3148" N, 119° 58' 57.5112" W
US


Red Flags: 
Whumphing noises, shooting cracks, or collapsing
Recent loading by new snow, wind, or rain
Obvious avalanche path

Observation made by: Professional Observer
Snowpit Observations
More detailed information about the snowpack: 

I waited until very late in the day to take advantage of an 8pm sunset, hoping for additional accumulation - the 6:30pm time is correct.

Pics #1 and 2: Very consistent test slope failures along Frog Lake Ridge on wind loaded slopes above 35 degrees. Weak layer was lower density layer within the storm snow, observed between 5 to 10 cm above old snow interface, buried by 5 to 25cm of additional storm snow.

Pic #3: Graupel layer observed consistently just above old snow. However, graupel was suspended in warm PPs, bonding well to old snow layer. Old snow layer consisted mostly of melt forms, with an occasional crust observed. No informal tests showed this to be a weak interface.

I fully expected slab conditions to exist on Elephant's Back - but oddly there was both less deposition and no evidence of slab formation. While new snow deposition measured 35cm in wind loaded pockets along my approach, Elephant's Back held only 20cm of new snow.

By the time of my departure around 7:30pm, 2-5cm of very low density PPs had accumulated. New snow stratigraphy consisted of the warm layer of PPs and Graupel bonding well to old snow, the lighter snow that acted as a weak layer on test slopes and mitt pits, a denser layer above this, and a fresh low density layer at the surface that produced loose snow results on those test slopes that didn't fracture on the deeper weak layer.

Snowpack photos: 
Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
100% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Light
Precipitation: 
Snow
Air temperature trend: 
Cooling
Wind Direction: 
Southwest
Accumulation rate: 
Less than 1 in. per hour
More detailed information about the weather: 

Calm to Light winds, though flagging on trees provided evidence of previous wind transport: