Pro Field Report

Basic Information

Observation Details

Observation Date:
December 14, 2019
Submitted:
December 15, 2019
Observer:
SAC - VandenBos
Zone or Region:
Sawtooth and Western Smoky Mtns
Location:
Headwaters to Smoky

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
Widespread
Collapsing? 
Widespread
Widespread cracking and collapsing as I traveled, slightly touchier on shaded aspects but present from northeast to southeast on the west half of the compass. Did not travel on east, but assume the same is true.

Snow Stability

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

Bottom Line

Continued cracking, collapsing, and remote triggering are clear indicators that avalanche hazard will not be decreasing quickly. Snowpack is complex, with several different surface hoar layers, crusts with facets, and depth hoar near the ground. Additional loading will reactivate this problem easily.

Media/Attachments

These avalanches were remotely triggered from the ridgeline above, approximately 400' along slope. S-SE aspect at 10,000' in the Smoky Mountains south of Bromaghin Peak. They failed on a layer of faceted snow grains on top of a stiff, icy melt-freeze crust.
These avalanches were remotely triggered from the ridgeline above, approximately 400' along slope. S-SE aspect at 10,000' in the Smoky Mountains south of Bromaghin Peak. They failed on a layer of faceted snow grains on top of a stiff, icy melt-freeze crust.
These avalanches were remotely triggered from the ridgeline above, approximately 400' along slope. S-SE aspect at 10,000' in the Smoky Mountains south of Bromaghin Peak. They failed on a layer of faceted snow grains on top of a stiff, icy melt-freeze crust.
This natural avalanche released in the Sawtooth Mountains north of Williams peak on a SE aspect at 8,700' at the tail end of the most recent storms. Older debris from avalanches that failed during the storm is also visible.
The large natural avalanche on the right side of this photo released at the end of the recent storm cycle in the Sawtooth mountains north of Williams peak on a NE aspect. Another natural avalanche is visible on the left side of the photo on a SE aspect.
This large natural avalanche released at the end of the recent storm cycle in the Sawtooth mountains north of Williams peak. Crowns are visible spanning the width of this photo.
This large natural avalanche released at the end of the recent storm cycle in the Sawtooth mountains north of Williams peak. Crowns are visible spanning the width of this photo.

Advanced Information

Weather Summary

Cloud Cover:
Mostly Sunny
Wind:
Moderate , N

Occasional S-1 flurries through the day with no significant accumulation. 2cm overnight based on sled tracks from yesterday. Wet north wind blowing steady moderate in upper elevations, transporting small amounts of snow.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Comments Photo
Several X, Meadow Bowl
8,500-9,200' 		D2.5 SS O-Old Snow N-Natural NE-SE aspects, several different crowns visible, based on depth most seemed to be activating 12/7 interface, but some deeper portions may have been picking off weak snow at 11/26. These layers are pretty close together in the Sawtooths, so it may just be heavy wind loading that was causing differing crown depths. Low certainty. None
1 N face Williams apron
N 		Deeper crown in heavily spindrift loaded location below N face of Williams. Could not see much glassing. None
1
NE 9,500 		D2 SS O-Old Snow 40-60cm AS-Skier
r-Remote 		Triggered from ridgeline above, 100-150m away along slope None
cluster of 3 Blind canyon
S 		D2 SS O-Old Snow AS-Skier
r-Remote 		S-SE aspect. Triggered from ridgeline above, 100-150m away along slope. Failed on top of MFcr with facets. I was able to find some SH grains here as well, but not enough to convince myself that it was a primary culprit. Slab was wind stiffened, approaching 1F+ hardness in places None

Surprising lack of natural activity in the Smokys, particularly given how touchy the snowpack appears to be. I could find a few smaller piles of mid-storm debris below obvious paths (D2 estimated based on debris) but less than I expected. Sawtooths look like they put on a show, based on brief glassing from highway. Would be interested in looking at crowns and seeing what the culprit in the upper pack was. I found plenty of SH buried at 12/7 interface when I was there 12/10, and plenty of (then) unburried

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: 12/7 down 40-60cm
Comments: SH and FCsf buried on 12/7. With our without a crust, depending on aspect.

Terrain Use

Avoided avalanche terrain that had not already avalanched. Avoided runouts below avalanche paths that could be triggered remotely.