Close
PROFESSIONAL OBSERVATION FORM
 Start Date: 03.04.19 End Date: 03.04.19 Name: Savage - OFF DUTY Operation: SAC
 Drainage/Route:  Williams Yurt: Profile, Marshall, Skier's Summit area - OFF DUTY Observed Terrain:  6500-10000', all but west Zone/Region:  Sawtooth Mountains
WEATHER OBSERVATIONS
 HN24: 20cm HST: 25cm Sky: Precip: Temps:
 Ridgeline Wind:
 Blowing Snow: Snow Available for Transport:
 Comments: Mostly clear to PC Monday and Tuesday AM, OVC Tues PM, 5cm snow Tues night, warm (above 32F at 8500') Wednesday, snowing Wed night (25-28F) and Thurs AM. Warm Thursday with obscured skies but trying to clear a bit by 1 PM. Not much wind-loading at middle elevations throughout the 4 days. Minor wind loading upper elevations prior to Wednesday night, unknown wind effects Wed night and Thursday.
AVALANCHE OBSERVATIONS
None Reported
 Comments: Slide on S-SE side of Williams Peak was very big: D3 or D3.5, running full track to the little lake (Yurt Lake) in the Profile drainage of Fishhook Creek. Ben noted persistent slab on SE face of Merrit Peak and cornice triggered slides up-drainage from Merrit in Goat Creek.
SNOWPACK OBSERVATIONS
 HS: 200-270cm 8000-9200' (prior to 20cm new snow last night) 
 Upper Pack: SW-S-SE=new crusts and FC above and below (3/5 and 3/6), sandwich of crusts and FC on some aspects and elevations. Widespread 3/6 crust due to both temperature and limited solar input was buried last night - this crust froze above about 7800' and was still "gooey" below that. On Wed 3/6, snow was wet down 10cm on S-SE aspects near 8000'. Below the crusts, well-graded DF from last week's big storm. 
 Middle Pack: 2/2 or 2/23? razor crust 100-130cm down, was sporadic in distribution but most prominent on SE. I probed for several hours searching for it on Tues 3/5 in the Marshall drainage.  
 Lower Pack: Not observed except in thin, alpine areas. Some basal FC but mostly rounds.  
AVALANCHE PROBLEM ASSESSMENT
Avalanche Characteristics
Character/Avalanche Problem:
Wind Slab

Layer/Depth:
15-100cm

Likelihood of Triggering
Sensitivity:
Stubborn

Spatial Distribution:
Specific
Terrain
  Primary Concern Comments: Fresh wind slabs that formed this week were touchy on >40* slopes. Older, thick wind slabs from last week weren't cracking. Probably unreactive or stubborn, but we didn't push it and avoided them.
 
Avalanche Characteristics
Character/Avalanche Problem:
Persistent Slab

Layer/Depth:
100-130cm

Likelihood of Triggering
Sensitivity:
Not Observed

Spatial Distribution:
Isolated
Terrain
  Problem 2 Comments: We avoided wind-loaded, SE facing slopes over 35 degrees except for traveling in tracks/paths that had already run.
 Comments: I expect the recently buried crusts and facets will be touchy where/when loaded. Even subtly wind-loaded, steep SW-S-SE-E aspects should be considered guilty until proven innocent.
STABILITY TESTS
 Stability Test Results: Many hand pits and quick non-standard tests revealed no clean shears in the upper 2 feet of the snowpack.
SNOW STABILITY
 Snow Stability Rating for your observed area: Good Confidence: HIGH Trend:
 Comments (aspects and elevations of instability, etc): We avoided traveling on or under most steep, SE-facing paths. Stability was good everywhere we traveled, no signs of instability.
BOTTOM LINE
 Comments: My general feeling is the snowpack in this area is turning the corner towards a "what you see is what you get" scenario. The caveats are 1) the persistent issue involving a February weak layer on SE aspects that produced large and very large slides on the SE face of Williams, in Meadow Creek Bowl, and on Merrit Peak and 2) the recently buried crusts and facets on SW-S-SE-E aspects. Because we were on a recreational trip, we avoided terrain with the deeper persistent issue and didn't carefully evaluate it. We also stayed away from very steep, consequential sub-alpine slopes peppered with rocks and trees (trigger points) - an example is the path above Lower Marshall Lake. We skied steep (38 to over 50 degrees), shady terrain that had obviously seen avalanches run during last week's storm.
FILE ATTACHMENTS

190305_YurtLake_runout.jpg
Carnage in the avalanche path below the SE face of Williams Peak, just above the little lake that drains into Fishhook Creek near 7700' in elevation. This slide ran full track, taking out some of the few remaining mature trees in it's way.