poor structure, shallow coverage and variable surface conditions on the Mammoth crest

Red Cone
Submission Info
Wednesday, December 23, 2020 - 12:15pm
Red Flags: 
Recent avalanche activity
Whumphing noises, shooting cracks, or collapsing
Recent loading by new snow, wind, or rain
37° 35' 45.0276" N, 119° 1' 20.1864" W
Snowpit Observations
More detailed information about the snowpack: 

Clear skies and cool temperatures made for a pleasant day as I made my way to the Mammoth Crest this morning. Moderate to strong winds were blowing out of the East South East and were moving quite a bit of snow around on the ridge top. Not quite enough wind to produce obvious flagging but certainly enough to deposit some fresh wind slab.  I found a few small terrain features with sensitive wind pockets (2”-6” in depth and 1F/4F) on a Northwest aspect near tree line.  And I was also able to sniff out a few small sensitive areas below tree line on a North aspect that cracked under my weight. These areas further down are likely deposits from the strong winds on the night of the 21st.  The alpine is largely scoured, and coverage is very sporadic above tree line. I did not one area near the feature named Jaws that appeared to have a recent avalanche. Recent wind loading appeared to have largely filled in the path and I suspect no larger than size d 1.5 (See photo below) it Was hard to judge from where I stood but I would suspect this failed during the wind event on the night of the 21st.

I dug in on an East aspect a bit above 10000’ very close to where I dug a pit about a week ago. My goal was to get a feeling for how much settlement has occurred during the last week of clear skies and warm temperatures and to monitor the lower snowpack for any change that may have occurred.  I found that quite a bit of settlement has occurred within the December snow. What was fist hard and largely unconsolidated a weak ago is now right-side up transitioning from 4finger to 1Finger.  The November snow on the ground is still weak as ever consisting of fist hard, loose sugary facets averaging around 2 mm in size. The facets on the ground at this location are bisected by a melt freeze crust about a cm thick. My inspections of the facets near the ground suggest that this base is continuing to weaken, I noted facets have grown in size and I identified some cup shaped grains within the basal layer. At the same time the slab resting on top of the facets has condensed and stiffened. Stability tests supported these findings. I conducted 3 Extended column tests, all three of which propagated on the facet layer above the crust. The first, when I isolated the column, and the other two under moderate force on the 11th tap. See pit profile for more details, I’ve also included the profile from Dec 18th for comparison.

Periodic probing along both my ascent and decent identified large variability in the coverage as well as the distribution of this poor structure. I noted an average snowpack depth between 30 and 60 cm (1-2 feet) between lake Mary at around 9000’ and the top of the crest at around 10400’, on Northwest- North-East aspects. while I found this structure to be prevalent throughout the shaded aspects. I suspect the shallow nature of the snowpack in general limits the areas where a sizable avalanche could occur on the lower facets.

Surface conditions were also quite variable with some solar aspects presenting a melt freeze crust up to about 1 cm thick. In more exposed areas near and above tree line I found a variety of wind stiffened snow ranging from soft and textured, supportable and hard, to breakable and unpredictable.  

They say variety is the spice of life and I must say the variable surface conditions along with the shallow obstacle ridden coverage certainly kept me on my toes as I made my decent today.

Snowpit or crown profile photo or graph: 
Snowpack photos: 
Snowpit videos (tests, etc): 
Weather Observations
Blowing Snow: 
Cloud Cover: 
Air temperature: 
Below Freezing
Wind Speed: 
Air temperature trend: 
Wind Direction: 
Accumulation rate: 
More detailed information about the weather: 

Clear skies and cool temperatures made for a pleasant day in the mountains today while moderate to strong winds kept me from an extended rest on the ridge top. Some wind transport was noted near tree line today.

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