Pro Field Report

Basic Information

Observation Details

Observation Date:
January 31, 2023
Submitted:
January 31, 2023
Observer:
SAC - Davis
Zone or Region:
Sawtooth and Western Smoky Mtns
Location:
Upper Vienna (All aspects, 7,300-9,600')

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
Isolated
Collapsing? 
Isolated
Very small wind slab in the Boulder Mtn foothills (see photo). Fresh-looking debris in a gully off of Abe's (see photo). I didn't observe any other additional natural avalanches. I had milky light but should have been able to see good-sized debris piles. The cracking I experienced was isolated to wind-loaded ridge caps.

Snow Stability

Stability Rating: 
Good
Confidence in Rating: 
Moderate
Stability Trend: 
Improving

Bottom Line

I did not observe any large obvious natural wind slab avalanches in this area. The weekend's storm snow formed soft 1-1.5' thick drifts that tapered quickly away from ridges. This storm snow is already very weak, a mix of facets and some surface hoar. The early January weak layers buried about 2' down were generally unremarkable where I looked. The snowpack below that is very strong and deep.

Media/Attachments

This small avalanche released on Abe's Armchair at the mouth of Smiley Ck. Poor light and recent wind-loading obscured the start zone, but it appeared to be a thin wind slab. E aspect at 8,800'.
Very small wind slab lee to N wind. Boulder Mtn Foothills.

Advanced Information

Weather Summary

Cloud Cover:
Mostly Cloudy
Temperature:
5-10F
Wind:
Light , W
New/Recent Snowfall:
HST since (1/27) = 15 cm @ Hwy, 25-30 cm near weather stations.

Broken skies. A few hours of passing snow showers midday. Very light snowfall in the White Clouds, near Galena Pass, and in Smiley Ck. No local accumulations. The wind was intermittently sifting snow at upper elevations but not actively loading.

Snowpack Observations

NE @ 8,200'; HS = 175 cm; Sheltered, open, planar slope: (1/5) down 50 cm presented as 1-2 mm FC. The overlying slab was F to 1F at the base. ECTX (x3), CTH 29 (RP). The mid-pack here was meaty showing P- to P+ hardness down to 11/27. Basal facets were rounding. The weakest interval I could find in this 40 cm thick layer was 1F hardness.

N @ 8,900'; HS = 183 cm; Sheltered opening, possible previous wind-affect: (1/5) down 53 cm presented as 1-2 mm FC. The overlying slab was F to 1F at the base. ECTP27 and 33, ECTN24. Mid-pack below this was again very strong showing P to P+ hardness.

(1/27) "new/old": This interface is all kinds of messed up looking. The recent snow was roughly split in half with the upper half looking like fairly normal DFs and the lower half as well developed FCsf. This sat atop a variety of 3-4 mm SH, crust + FC combos and simple FC in others. I'd assume any recently formed slabs are sensitive. I looked for them, and only found them on and very near ridge caps.

Alpine funk: I found hard, sometimes hollow sounding slabs of varying thickness sitting atop a pile of rotten facets along shallow, rocky, wind affected ridges. These likely formed during high wind last week.

Early January weak layer of small facets. I did not find surface hoar in the two sheltered, shaded locations I dug. N aspect @ 8,900'.

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: 50 cm
Weak Layer(s): Jan 5, 2023 (SH)
Comments: I did not find SH in this area. This layer presented at 1-2 mm FC. ECTP 27 and 33. Several ECTXs. Shaded where observed.
Persistent Slab
Isolated
Specific
Widespread
 Unknown
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
 Layer Depth/Date: 30 cm, 1/27
Comments: This may be a real persistent slab problem where wind has built a stiffer slab. I did not find it here but I was certainly looking for it.

Terrain Use

Solo travel. I avoided avalanche terrain.