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PROFESSIONAL OBSERVATION FORM
 Start Date: 01.19.18 Name: Wieland, VandenBos Operation: SAC
 Drainage/Route:  McDonald Observed Terrain:  7300-9300 Zone/Region:  Sawtooth Mountains
WEATHER OBSERVATIONS
 HN24: 12-20cm HST: 12-20cm Sky: X Precip: S1 Temps:
 Ridgeline Wind:
 Blowing Snow: Snow Available for Transport:
 Comments: Calm wind in AM increasing some in afternoon with squall and S1 around 1430. Clouds dissipating near Galena at end of day.
AVALANCHE OBSERVATIONS
 No. Location Date Size Type Trigger Aspect Elevation Comments
 2 or 3 McDonald Today AC N 9100 Were D2.5 or pushing D3.
 Comments: Dropped two large cornices and get several large avalanches failing mostly 1.5-2.5' deep with max crown approaching 3' near ridge. Went further down ridge and saw that another slope had pulled out at some point during these other slides all the way back up to ridgetop.
SNOWPACK OBSERVATIONS
 HS: 170cm @ 8900' ENE, 115 cm @ 8200' E 
 Upper Pack: 12-20cm low density PP. 8900': 12/19 down 95cm, ECTX. 8500': 12/19 down 65 and weaker than found in upper pit. ECTP 13. 
 Middle Pack: Thanksgiving crusts down 80-120cm. 
 Lower Pack: Very weak moist, facets near ground @ 7300'. Stronger when found under thanksgiving crusts. 
AVALANCHE PROBLEM ASSESSMENT
Avalanche Characteristics
Character/Avalanche Problem:
Persistent Slab

Layer/Depth:
12/19

Likelihood of Triggering
Sensitivity:


Spatial Distribution:
Widespread
Terrain
  Primary Concern Comments: Did not step into avy terrain, but persistent was reactive with large triggers.
 
Avalanche Characteristics
Character/Avalanche Problem:
Wind Slab

Layer/Depth:


Likelihood of Triggering
Sensitivity:
Not Observed

Spatial Distribution:

Terrain
  Problem 2 Comments: Didn't get into alpine terrain but evidence of wind affected snow was visible.
STABILITY TESTS
 Stability Test Results: ECTX in upper pit and ECTP13 in lower pit.
OBVIOUS SIGNS OF INSTABILITY
 Marked with checkmark if observed:
 Cracking (widespread)    
 Collapsing (widespread) Depth: 30-40cm  
 Comments: Widespread collapsing and cracking 7300-7800 but ended after that. Seemed to be associated with rain line from several weeks ago.
SNOW STABILITY
 Snow Stability Rating for your observed area: Confidence: Trend:
BOTTOM LINE
 Comments: Initial collapsing down low on every slope we touched was surprising but quickly ended with some elevation gain. Crown heights, especially where they tapered near rocks/edges still in the realm of human triggering. Impressed on how far over and upslope the last crown we saw down the ridge pulled out. First slide we triggered had an impressive cloud and force when it hit the moraine/runout.
FILE ATTACHMENTS

DSC_1161.JPG
Collapse triggered at ~7,500'.

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Sympathetic persistent slab release. Most likely occurred when we dropped cornices on the slope 300-500' away. North aspect @ 9,100'.

DSC_1224.JPG
Extensive debris from large sympathetic release described in previous photo and above in avalanche observations section.

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