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Professional Field Report

Basic Information

Observation Details

Observation Date:
April 7, 2020
Submitted:
April 7, 2020
Observer:
SAC - Savage
Zone or Region:
Soldier and Wood River Valley Mtns
Location:
E Fork Baker Ck-Fox Peak: 6700-9100' (on the border between Soldier&WRV zone and Galena&E Mtns zone

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
None Experienced
Collapsing? 
None Experienced
Avalanches are listed below. I spoke to another party who was skiing in the Baker Ck drainage within a few miles of Baker Lake. They experienced a couple snowpack collapses on E aspects.

Snow Stability

Stability Rating: 
Poor
Confidence in Rating: 
Moderate
Stability Trend: 

Bottom Line

I saw 3 large, fresh, natural slab avalanches (see below), 2 with crowns hundreds of feet wide, on a variety of aspects. I observed many (over 60) small wet loose slides involving the surface snow. Most of these were not big enough to bury people. The snowpack held together enough today to prevent full depth wet loose avalanches where I traveled, but the buried crusts on lower elevation slopes and westerly middle elevation slopes may not hold up with the continued heat+sun in the coming days. Cornice fall may become an issue as well this week.

Advanced Information

Weather Summary

Cloud Cover:
Mostly Sunny
Temperature:
50s F parking lot, near 40F Fox Peak
Wind:
Light , SW

There was enough of a breeze at the middle/upper elevation transition to help cool SW and W aspects in the afternoon. The partial afternoon cloud cover also helped keep NW/W/SW aspects just cool enough to prevent full depth wet loose avalanches where the snowpack was thin.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Comments Photo
5 Lake Ck - Triple Peaks, Sun Mtn
NW 7300-8400 		D1 WL N-Natural Several small wet loose slides and lots of rollerballs on NW and W aspects. None
1 Bear Peak - Thompson Ck/Warm Springs Ck
NE 9200 		D2.5 U N-Natural Crown was 300-400' wide, easily visible with the naked eye from 10 miles away in the shadows, estimated 3 ft thick. It looks like it may have been triggered by a smaller sluff coming from above.
(4-7-20) This slab avalanche is approximately 3 feet thick and 300-400 feet wide. It released on a NE facing slope near 9200' on Bear Peak.
1 Boulder Peak
S 10000 		D3 SS N-Natural Over 1500' wide natural slab avalanche on SE face of Boulder Peak, spanned SE-S-SW aspects in bowl. It's big. May have been triggered by small wet loose on the looker's left side of the crown, or could have released initially as a slab. Note: Ben's photo on media page shows another part of the crown that is out of the frame in this photo.
(4-7-20) This large slab avalanche released on SW-S-SE aspects near 10000' on Boulder Peak sometime Tuesday or Wednesday. The crown is over 1000' wide.
over 60 Smoky and Boulder Mtns
SE alpine 		D1.5 WL N-Natural Dozens of relatively small, natural wet loose avalanches in E-SE-S-SW-W facing terrain in the Boulders Mtns, Silver Ck, Newman Ck, Norton Ck, and Baker Ck drainages. Some were point releases, some were triggered by cornice fall. None
1 Newman Ck - Baker Ck
E 8900 		D2 SS N-Natural
(4-7-20) This slab avalanche released on an E aspect near 8900' in the Newman Ck drainage.

Snowpack Observations

Lower elevations: entire snowpack was moist, percolation columns established on some aspects/slopes and not on others. Rollerballs on 30-35* shady terrain.
Middle elevations (7200 to about 8800') Fox Peak: Small surface hoar from last night (should/will melt in the coming days), upper 10-15cm was mostly a mix of crusts, graupel (especially around 7800'), decomposing fresh snow. No crust on due N, cream cheese powder on W/NW. Very little wind with the last storm.
West=HS100-125cm with a couple crusts staying frozen in the middle of the snowpack; without the crusts, it was all moist/wet and ugly.
W/NW 8800'=HS 130cm, top 5 cm very wet/pooling water; ECTX (I only tested down about 60cm to just below the FC that formed in Feb and March)
NW 8950=HS 145cm, top 3cm was wet; ECTN18@105cm (3/29 interface), ECTN26@87cm (FC buried on either 3/7 or 3/14), no results on older larger FC 70-77cm (1F/P, fairly strong).
I did not see the dirty layer in any pits I dug today. This surprised me as the dirt layer was very obvious near Baker Lake a few weeks ago.

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: estimated 60cm
Comments: Stability tests did not show instability in the FC layers from early March on fairly exposed, NW and W-NW aspects around 8800-9000'.
Wet Loose
Isolated
Specific
Widespread
Unreactive
Stubborn
Reactive
Touchy
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
 Layer Depth/Date: Upper 15cm (6")
Comments: Specific to above about 8000' where significantly more snow fell this week. Sheltered E-S-W facing slopes approaching 40* were the bullseye. I did not spend much time on NE-E-SE aspects.

The Bear Peak and Newman Ck natural slides fit the picture we've been working with (FC layers on NW-N-NE-E facing slopes 8400-10000' have issues). The Boulder Peak slide on a sunny aspect is a new angle to consider; hard to say if it was the"perfect" wind loading on a crust or if there is a more widespread persistent slab problem on sunnier aspects. With all the crusts that have been buried in the past few weeks, it wouldn't surprise me to find one that isn't happy with the snow above it and produces more than just an outlier avalanche.

Terrain Use

I avoided all large and/or consequential starting zones. I spent minimal time in the tracks and runout zones of large paths directly facing the sun.

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