Pro Field Report

Basic Information

Observation Details

Observation Date:
December 3, 2019 - December 3, 2019
Submitted:
December 5, 2019
Observer:
SAC - Chago
Zone or Region:
Mores Creek
Location:
Pilot Peak (8050 feet, NNW)

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
Isolated
Collapsing? 
Widespread
Uncharacteristically shallow snowpack, 30-40 cm independent of elevation or aspect. Snow from the last two storms rests above a relatively cold (4 Deg-C) 5 cm thick layer of large melt-freeze crystals. Sandwiched between new snow and basal crust layer there is a 0.5-1 cm layer of reactive ~2 mm rounded facets.

Snow Stability

Stability Rating: 
Poor
Confidence in Rating: 
Low
Stability Trend: 
Steady

Bottom Line

Shallow snowpack with a reactive persistent slab problem raises the stakes if caught even in a small slide (fairly common at Pilot Peak bowl).

Media/Attachments

Snowpit at Pilot Peak, ~8000 feet, NNE, 22 deg slope, HS 35-40 cm
Rounded basal facets, ~ 2mm, 35 cm from the snow surface
Interface between MF layer above ground and new snow.

Advanced Information

Weather Summary

Cloud Cover:
Obscured
Temperature:
-2 to +2 Deg-C
Wind:
Light , NW

Warming trend. Temps exceeding 0 Deg-C.

Avalanche Observations

No slab avalanche releases observed. Wet loose releases at I-21 road cuts at 5600-6100 feet elevation range.

Snowpack Observations

I was surprised about the 5 cm crust layer above the ground. The persistent weak layer (35 cm) rests above this crust. The slab consists of two rapidly rounding/sintering layers (15, 23 cm from the surface) of the most recent snow. Stability test results: CT1SC, ECTP11, CPST22/100(END), PST35/120(END). All fracture planes at 35 cm depth from the snow surface.

Snowpit at Pilot Peak, ~8000 feet, NNE, 22 deg slope, HS 35-40 cm
Interface between MF layer above ground and new snow.

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
Persistent Slab
Isolated
Specific
Widespread
Unreactive
Stubborn
Reactive
Touchy
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
 Layer Depth/Date: 35 cm /20191203
Comments: Persistent slab problem not present below 7400 feet, irrespective of aspect.

Warm temps assisting in the development of a more cohesive slab. Even though the basal facets have undergone rounding, whumping and reactive test results suggest that the combination of a shallow slab, persistent crystals, and the melt-freeze layer below the slab/weak layer structure might become even more reactive with additional loadings, such as next weekend storm.

Terrain Use

Stayed on Pilot Peak Road. Shallow snowpack and snow-covered rocks/underbrush/dead-fall impede safe skiing. Avoided avi starting zones at Pilot Peak bowl due to numerous whumps. Was traveling solo thus did not approach > 30 Deg terrain to perform ski test.