Weak Snowpack Structure - Mammoth Crest

SNOWPACK OBSERVATION
Red Cone Shoulder
Submission Info
Member
Wednesday, December 30, 2020 - 2:00pm
Red Cone Shoulder 37° 35' 48.3792" N, 119° 1' 26.58" W
Snowpit Observations
More detailed information about the snowpack: 

Toured up to Red Cone today with mild temperatures and ocassional Light winds blowing out of the Northwest.

At the shoulder of Red Cone we stopped to look at the Facets at the bottom of our snowpack.  The snow depth at 10200 feet on a NW Aspect was thinner than expected.  And we certainly found the weak structure we've been seeing everywhere.  The interesting thing was the varying thickness of the facet layer in the hasty pits we dug.  Thickness of the Facet Layer ranged from 3cm to 16cm and the overlying slab ranged from 36 to 60cm.  All the facets were in the Fist to 4f hardness range and all the slab hardness was 1 finger closest to the Facets adn gradually moved to Fist hardness near the surface.  This was similar structure to what we have been seeing in a certain elevation range and aspect in the Mammoth Lakes Basin.

Photos 1 through 5 show the differences in thickness of the Snowpack, the Slab and Facet Layer.

Here is a breakdown of what each of these profiles looked like.

Photo 1: HS 47cm Slab 44cm Facet Layer 3cm Facet Hardness 4f

Photo 2: HS 70cm Slab 60cm Facet Layer 10cm Facet Hardness 4f

Photo 3: HS 63cm Slab 47cm Facet Layer 16cm Facet Hardness F

Photo 4: HS 52cm Slab 36cm Facet Layer 16 Facet Hardnes F+

Photo 5: HS 60cm Slab 48cm Facet Layer 12cm Facet Hardness F

This is certainly a lot of data about distribution, but it doesn't tell us a lot about likelyhood of triggering.  For example; on this slope which was in the mid 20 degree range we didn't see any signs of instability like collapses or shooting cracks.  Column tests on other slopes nearby are showing mixed results.  This tells me the Persisten Slab problem isn't really gone it is just rare to find a place where the slab is stiff enough(or heavy enough) and the weak layer is weak enough to get an avalanche. We'll see what happens when 2 to 4 inches of water load our current snowpack. Fingers crossed for that!

Snowpit or crown profile photo or graph: 
Snowpack photos: 
HS 47cm Slab 44cm Facet Layer 3cm Facet Hardness 4f
HS 70cm Slab 60cm Facet Layer 10cm Facet Hardness 4f
HS 63cm Slab 47cm Facet Layer 16cm Facet Hardness F
HS 52cm Slab 36cm Facet Layer 16 Facet Hardnes F+
HS 60cm Slab 48cm Facet Layer 12cm Facet Hardness F
Any other comments about the observation or links to outside pages that have more info on the observation: 

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Weather Observations
Blowing Snow: 
No
Cloud Cover: 
25% of the sky covered by clouds
Air temperature: 
Above Freezing
Wind Speed: 
Light
Precipitation: 
None
Air temperature trend: 
Warming
Wind Direction: 
Northwest
Accumulation rate: 
None
More detailed information about the weather: 

As I said above it was mild.  The wind blew from the NW when we stopped on ridgelines and bordered on Moderate at its max gust.

Lake George Ridge:

1200 hrs 9220ft NW Aspect

Tair 3.5 degrees C Tsurface -1.0 degrees C T20 -3.5 degrees C

HS 73cm HST 25cm

Ski Pen 10cm Boot Pen 25cm

Winds L from the NW maybe with a Moderate gust No Blowing Snow

Overcast Skies with thin cloud. 

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