Pro Field Report

Basic Information

Observation Details

Observation Date:
February 20, 2022
Submitted:
February 21, 2022
Observer:
SAC - VandenBos (off duty), Gall
Zone or Region:
Sawtooth and Western Smoky Mtns
Location:
Fishhook (6,500-9,200, primarily NW-N-NE up high, all aspects down low)

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
Isolated
Collapsing? 
None Experienced
Avalanches observed refers to small, intentionally triggered slabs and sluffs. Cracking in thin, freshly deposited wind drifts. In places, cracks extended 20-30' feet from my ski tips. I selected "none experienced" in collapsing because we could not feel the collapsing that must have been accompanying the small slabs we were triggering.

Snow Stability

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

Bottom Line

The 3-4" of new snow that fell created small wind drifts and slabs that were reactive to my weight. Most of these slabs were less than 6" thick, but were reactive on steep slopes.

Media/Attachments

Ben found thin but sensitive wind drifts in upper elevation terrain in the Sawtooths on Sunday, 2/20. The slab pictured was only a few inches thick but was still able to propagate fractures 20-30' away from the trigger point. In steeper terrain, similar slabs were picking up speed and material rapidly as they traveled downslope.

Advanced Information

Weather Summary

Cloud Cover:
Obscured
Wind:
Moderate , W
New/Recent Snowfall:
1cm at Ranger Station, 3-5cm along the moraine, 6-10cm higher in the mountains.

Mild temperatures to start the day, with light snowfall beginning around 10:30. Temperatures slowly decreased through the day. Winds blowing at light to moderate speeds with periodic short gusts in the strong range, first out of the W/SW, then switching around to NW as the day ticked by.

Avalanche Observations

We triggered some D1 sluffs and thin wind slabs involving the new snow. No other avalanche activity observed.

Snowpack Observations

The combination of 6-10cm of new snow and variable winds were enough to build some very small, sensitive wind slabs. The thickest slabs we encountered were in the 15-20cm range, though only the upper portion of these were reactive. It appeared that the very small slabs we were able to trigger were failing on a density change/crystal change within the new snow. Dry loose sluffs and small slabs that we triggered were able to pick up speed quickly as they traveled downslope, thanks to the dense, older snow surface underneath, though it seemed like you needed to be on a slope approaching about 40 degrees to make this happen.
We also encountered quite a few older, stiffer slabs that were unreactive. These were variably distributed and P hard. We avoided them for the most part, to limit hazard and for ease of travel.

Avalanche Problems

The new snow didn't create a single, well-defined avalanche problem, but we were mindful of small wind slabs and dry loose sluffing..

Terrain Use

We exercised caution around wind-loaded areas and in steeper, rockier terrain where the consequences of being caught in a small slide were high. We avoided one very steep slope that had a recent wind slab.