Observation: NWAC Observer

All Observations

Basic Information

Observation Date:

December 24, 2022

Submitted:

December 24, 2022

Observer:

NWAC Observer - Willie Webster

Zone or Region:

East North

Location:

Highway 20 near Silver Star gate (North aspects 3000' to 6900' )

Recent Avalanches?

Yes

Cracking?

Widespread

Collapsing?

Isolated

4-10" storm slab release on all rolls and slopes greater than 35 degrees

Roller balls during the warm up at 6800' in the silver star mountain zone. It was 0 degrees C here, and below 6000' it was -11 degrees C (12 degrees F).

A pit wall on the north facing aspect at 4000'. Only about 80 cm deep here. Larger facets on the ground. Smaller facets in the middle snowpack. New snow and faceting decomposing fragments make up the upper snowpack.

Small facets make up the middle snowpack. .3-1 mm

Facets found at the bottom of the snowpack. 1-3 mm

Just some big surface hoar. In this case it's called cavity hoar. It's been cold. 4000'

https://youtu.be/qVnqwfQyOjc

Advanced Information

Cloud Cover:

Overcast

Temperature:

12 to 32°F

Wind:

Light , W

New/Recent Snowfall:

7" new storm snow fell while in the field

Heavy snowfall throughout the day. At elevations below 6000' temps were low at about 12 degrees F. As we travelled above 6000' we entered the warm front and found temps around 32 degrees F.

Avalanche Observation Comments:

Widespread D1 avalanches on small convex rolls observed. Visibility and conservative terrain choices kept us from seeing any larger slopes.

We dug a pit at 4000' and found a very weak and low density snow pack and about 80 cm deep. There are 1-3 mm facets over the ground. The middle snow pack is also well faceted, but smaller grains (.3 - 1mm). New snow was piling up. Temps stayed cold at around 12 degrees F as we gained elevation. Near 5600' temps started to rise, and by 6000' we were in the warm air near 32 degrees. The new snow falling here is wet and cohesive; It's easy to make snowballs. At 6900' we dug another pit in a 140 cm deep snow pack. We found a similarly cold and weak lower and middle snowpack with relatively warm new snow on top. The middle snow pack here also had a little more structure and hardness than at the lower elevation. We performed a propagation saw test on the old 11/22 crust/ facets 100 cm down. See video. at 32 cm into the cut the 150 cm column propagated to the end. It seems the new snow is adding some dangerous cohesion/ slab characteristics above rather weak snow. There are other weak interfaces in the middle of the snowpack we didn't test. We saw many D1 storm slabs 3-10" deep on all manner of small convex rolls. It was a super interesting day to be out on low angle slopes well away from slide paths.

Problem	Location	Distribution	Sensitivity	Size	Comments
Persistent Slab	N E S W	Isolated Specific Widespread	Unreactive Stubborn Reactive Touchy	D1 D1.5 D2 D2.5 D3 D3.5 D4 D4.5 D5	Comments: There is the potential for avalanches to release on weak factes above the ground
Storm Slab	N E S W	Isolated Specific Widespread	Unreactive Stubborn Reactive Touchy	D1 D1.5 D2 D2.5 D3 D3.5 D4 D4.5 D5	Comments: The warmer temps and heavy precip made the top 3-10" of storm snow touchy

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