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Professional Observation

       

Basic Information

Observation Details

Observation Date:
November 29, 2022
Submitted:
November 29, 2022
Observer:
Everett Phillips | ESAC Forecaster
Zone or Region:
Mammoth Lakes
Location:
Mammoth Lakes area - Near Surface Facets

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
None Experienced
Collapsing? 
None Experienced

Key Points

Today’s tour in the Mammoth area was targeted towards surveying surface conditions ahead of Thursday’s storm.

  • Above Treeline multiple wind events left hard surfaces from bare rock to sastrugi. Snow cover is mostly limited to cross loaded terrain features such as couloirs and bowls.
  • NTL and BTL the snow surface consists mostly of crust-facet combinations. Crusts vary greatly in strength and thickness depending on wind and sun exposure.
  • Soft snow can still be found in forested N facing terrain.
  • SW and S aspects are mostly bare at all elevations.
  • The Mammoth Lakes area, and Mammoth Mountain and Lakes Basin in particular have a deeper snowpack than elsewhere in the forecast zone.

Media

9700', NNW, Mammoth Zone
Near Surface Facets found on the snow surface over a thin MF crust. 9700' NNW in a clearing between stands of trees.
Melt-Freeze crust part of a facet-crust combo forming at the snow surface from radiation recrystallization during the late November dry spell.
Minarets conditions
Ritter conditions
Ritter and Banner conditions

Advanced Information

Weather Summary

Cloud Cover:
Clear
Temperature:
28 F
Wind:
Calm

It was warm and sunny in the Mammoth area today.

Clear skies and a high temp. of 28 F at 10000′.

Calm winds at the observation site below treeline.

Light winds on ridges.

No precip.

Snowpack Observations

I dug a pit on a NNW aspect at 9700′ where the height of snow was 75cm and the slope angle was 10 degrees.

I found my layer of concern at the snow surface, where a thin Melt-Freeze crust was supporting a thin layer of .5mm to 1.5mm Near Surface Facets (FCsf).

It seems likely that this crust was formed by above-freezing air temperatures. I was able to find a similar crust in steep north-facing trees nearby. The combination of a temperature crust and a clear view of the sky at the observation site makes me think these FCsf were formed by radiation recrystallization.

In terms of spatial distribution this surface layer seems most likely to be found on sheltered NW, N, and NE slopes NTL and BTL where there is a clear view of the sky.

 

Terrain Use

Good riding can be found in isolated locations in the Eastern Sierra. The problem is getting to and from those areas safely. The approach and exit part of the day usually involve very thin snow cover and difficult surface conditions.

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