Pro Field Report

Basic Information

Observation Details

Observation Date:
February 18, 2021
Submitted:
February 18, 2021
Observer:
SAC - Davis, Savage
Zone or Region:
Galena Summit and Eastern Mtns
Location:
Avalanche Peak (WRV and Smiley Ck Sides) (All aspects, 7,700-9,400')

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
None Experienced
Collapsing? 
Isolated
We experienced a couple of small collapses in an area with a generally thin (< 1 m) snowpack on a S-facing slope at 9,100'.

Snow Stability

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

Bottom Line

Poor snowpack structure exists in thinner, rockier, and more wind-exposed areas around Avalanche Peak. Despite today's unremarkable snowpack test scores, these areas would not respond well to a rapid load.

Media/Attachments

Slab avalanche that failed near the mouth of Smiley Ck on a ENE-facing slope near 9,000'. The crisp looking crown indicates that this slide occurred near the end of our recent storms.
Snow pit on the Smiley Ck side of Avalanche Peak near Galena Summit on a SE facing slope at 9,050'.
Snow pit on Avalanche Peak near Galena Summit on a SE facing slope at 8,500'. The fracture occurred on a layer if facets at the 1/27 interface following non-standard loading.
Pit profile on Avalanche Peak near Galena Summit on a SE facing slope at 8,500'.

Advanced Information

Weather Summary

Cloud Cover:
Overcast
Temperature:
Low 20s
Wind:
Calm
New/Recent Snowfall:
30 cm settled storm snow since 2/11

High clouds moved in mid-morning and clouds thickened to proper overcast by about 1130 AM. The wind was calm where we were and no sign of wind moving snow on nearby peaks. No new snow had fallen as of 430 PM.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Photos Details
3 Feb 15, 2021
(+/- 3 days) 		Smiley Ck
N 9800ft 		D2 N-Natural Report
1 Feb 16, 2021
(+/- 1 day) 		Abe's Armchair - Smiley Ck
E 9000ft 		D1.5 SS-Soft Slab N-Natural
Slab avalanche that failed near the mouth of Smiley Ck on a ENE-facing slope near 9,000'. The crisp looking crown indicates that this slide occurred near the end of our recent storms.
Report
Smiley Ck
Abe's Armchair - Smiley Ck

We had good visibility into the southern Sawtooths from about Mattingly Pk to Decker Pk and did not observe much more than a handful of smaller sluffs and slabs.

Snowpack Observations

Total snow depths in sheltered areas were between 100-130 cm.

Avalanche Peak WRV, SE, 8,500':
The new/old (2/11) interface was down ~30 cm, presenting as a 1 cm melt-freeze crust on sunnier slopes. This layer doesn't strike me as one that will last long. ECTN26. The (1/27) interface was down ~70 cm and presented as a layer of facets. We did get an ECT to propagate after applying non-standard force. ECTP>30. (See profile).

Avalanche Peak Smiley Ck, SE, 9,050':
We sought to find these same PWLs in thinner, rockier terrain. The snow depths and stratigraphy changed quickly in the thinner, more heavily wind-affected areas so a "representative" slope isn't realistic. Generally speaking, we found a snowpack where snow since 2/11 makes up about a third to half of the snowpack. Beneath it was a stack of facets, similar to what I found on Galena Peak yesterday. I'd expect areas like these to react poorly to rapid loading. Test results were ECTNs. This is where our small collapses occurred.

Snow pit on Avalanche Peak near Galena Summit on a SE facing slope at 8,500'. The fracture occurred on a layer if facets at the 1/27 interface following non-standard loading.
Snow pit on the Smiley Ck side of Avalanche Peak near Galena Summit on a SE facing slope at 9,050'.

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
Persistent Slab
Isolated
Specific
Widespread
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
 Weak Layer(s): Dec 11, 2020 (FCsf)
Comments: This layer remains the most obvious, widespread weak layer to keep an eye on with additional loading. 1/27 looked worse in our shallow pit where the interface was more heavily faceted.

Terrain Use

We avoided skiing in or directly beneath consequential avalanche terrain.