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Professional Observation

       

Basic Information

Observation Details

Observation Date:
December 5, 2022 - December 5, 2022
Submitted:
December 5, 2022
Observer:
Clancy Nelson | ESAC Forecaster
Zone or Region:
Mammoth Lakes
Location:
Mammoth Lakes Basin - Whumpfing in the Deep

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
Isolated
Collapsing? 
Isolated
  • At 9725 feet, I got a deep, booming collapse that shook the snow out of trees 50 feet away on the west-facing side of a gully in an open forest. Complete with shooting cracks.
  • I dug and found that the cracks shot down to a layer about 45cm deep, where I got an ECTN12, and also on a layer of 2mm facets about 15cm above the ground. On the deeper layer, I got ECTP26. HS = 150. The slab was soft (4F over F over 4F). The deep facets were F hard.
  • I jumped on some previously wind-drifted slopes across the gully (NE facing) and got cracking and small slabs that broke out from under me.
  • I got some localized whumpfing on east-facing slopes at the same elevation.

Key Points

I took a quick day-off tour into the Lakes Basin and saw several signs of instability.

  • Whumpfing and cracking, mentioned above.
  • Propagating snow pit tests, mentioned above.

Media

Shooting crack from a booming whumpf that shook snow out of the trees 50 feet away. 9725', W aspect, Mammoth Lakes Basin
ECT results near a large whumpf. Propagation on 2mm facets near the ground. 9725', W aspect, Mammoth Lakes Basin
Small, soft wind slabs breaking on test slopes BTL. NE aspect, Mammoth Lakes Basin
Intense blowing snow NTL/ATL across the range between Mammoth and Bishop

Advanced Information

Weather Summary

Cloud Cover:
Mostly Cloudy
Temperature:
Below Freezing
Wind:
Light , SW

I expected it to clear up more than it did along the Mammoth Crest.

Light graupel showers off and on.

Winds were still blowing near- and above-treeline where I saw intense blowing snow, both in the Mammoth Area and along the whole range on my drive back down to Bishop.

Snowpack Observations

The surface and top inch of recent snow were graupel.

Ridges had supportable, 1F hard, wind drifts from the past 4 days. Drifts were between 10 and 50cm thick, even below treeline. Ski pen in more sheltered areas was 10-30cm. Boot pen was about a meter.

Terrain Use

I did not expose myself to any avalanche terrain today.

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