Professional Observation

Basic Information

Observation Date:

January 12, 2023 - January 12, 2023

Submitted:

January 12, 2023

Observer:

Clancy Nelson and Steve Mace | ESAC Forecaster

Zone or Region:

Bishop Creek

Location:

Aspendell Avalanche - Preliminary Report

Recent Avalanches?

None Observed

Cracking?

Isolated

Collapsing?

None Experienced

Isolated cracking in soft (4F) wind slabs that developed in the past 48 hrs (1/10-1/11). These averaged 4-24 inches thick on leeward slopes near treeline. We did not get above treeline.

Rollerballs we common below treeline on all aspects in the afternoon. Warm temps and high-hazy clouds warmed the cold, unconsolidated snow at the surface thanks to the greenhouse effect.

We went to Aspendell to investigate an avalanche that failed midday on January 9th. This is preliminary information. A thorough report is forthcoming.

Advanced Information

Cloud Cover:

Mostly Cloudy

Temperature:

38 F at 12:45pm at 9700 ft

Wind:

Light , SW

According to a witness, the avalanche occured midday on January 9th (20230109).
The avalanche ran on a NW aspect of Table Mountain, just north of Jawbone Canyon.
The start zone slope angle averaged 42 degrees. The overall slope angle of the avalanche path averages 38 degrees.
The crown elevation was 9700 feet. The vertical fall was 1250 feet.
The debris averaged 1.75 meters deep and filled an area 586 feet wide by 637 feet long.
It was a very large hard slab (slab density at least 1F hard) avalanche. A 110cm thick 1F-P wind slab avalanche stepped down to a deeper, 70cm thick P wind layer. The weight of the two wind slabs was enough to trigger a 30cm thick facet layer at the ground. HS-N-D3-R4-O.
We dug a snow pit 110 feet above the crown. This was the safest area to dig that had a similar snow profile. We confirmed that the same basal facets existed near the ground at the crown.
The debris and slab indicate that this was a dry slab avalanche. The weak layer near the ground was dry to moist.