Professional Observation
Basic Information
Observation Details
Observation Date:
December 24, 2021Submitted:
December 24, 2021Observer:
Steve Mace | ESAC ForecasterZone or Region:
Mammoth LakesLocation:
Mammoth rock areaSigns of Unstable Snow
Recent Avalanches?
None ObservedCracking?
IsolatedCollapsing?
None ExperiencedPeriods of heavy snow made it difficult to see the ridgeline today however significant wind transport was occurring even below treeline. We avoided avalanche terrain today but on several leeward test slopes, we observed Fresh wind deposits ~6-16″~ thick. hand pits and kick turn tests showed these areas to range in sensitivity.
We dug in at about 8,800′ on a NE Aspect. Total hight of snow= 190cm, hight of new snow =83 cm. Stability tests highlighted our layer of concern on a density change 57cm from the surface. Compression tests broke with sudden planar results and we saw propagation on this layer in our ECT. (CT14 SP @57cm from the surface, ECTP23@57cm from the surface.)
While requiring more force to initiate failure, an avalanche on this weak layer could be quite sizable.
Snow Stability
Stability Rating:
PoorConfidence in Rating:
HighStability Trend:
SteadyAdvanced Information
Weather Summary
Cloud Cover:
OvercastTemperature:
25Wind:
Strong , SW
Snow showers seemed to lull mid-day and we even saw a brief period of clearing skies before skies turned overcast again and snowfall rates increased around 2 pm. total snowfall during the day was about 5-7″
Winds were strong out of the SW even at lower elevations leading to significant snow transport and stiffening of surface snow in more open areas.
Snowpack Observations
What a difference a day makes! After the very wet and upside-down snow yesterday it was pleasant to find colder temperatures and lower-density snow falling from the sky. Overall Snow totals, today seemed to underperform the forecast with 5-7″ recorded on the porch here in Mammoth. I have no doubt that totals were higher at upper elevations and closer to the crest.
Surface conditions today were starting to stiffen up quite a bit from the strong winds even in more protected areas at lower elevations. winds were consistently blowing at strong speeds today and recorded values at the summit of Mammoth Mtn hovered around 100 mph this morning before the gauge stopped working. Our field observations suggest the risk of sizable storm slab avalanches remains although hard force was needed to initiate failure in our stability tests. More concerning was the potential for wind slabs today. significant amounts of snow was being transported throughout the day, and we found areas with significant deposits even below treeline.