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SIMPLE OBSERVATION FORM
 Date: 01.12.18
 Location:  West facing slope into creek basin feeding Bull Trout Lake Zone/Region:  Banner Summit
 Activity:   Avalanche
AVALANCHES TRIGGERED
 Was it intentional?  no
 What type of avalanches?   Hard Slab
 What size?
 Size 2: Could bury, injure, or kill a person
 What Elevation?  7800 to 7900
 What Aspect?   W
 Comments: West facing slope. Trigger was on approx 25 to 28 deg slope, propagated to slightly steeper slope angle where slide initiated. Crown was approx 150ft wide, 1.5 to 2.0 feet deep. Slide path was straight down from crown (150 feet wide), running approx 300 feet, stopping on shallower angle terrain (25 deg). No portion of the crown was safely accessible to evaluate what layer the slide ran on. We assume the slab was windpack, but cannot be sure. Crown height was large enough that it may have stepped down to persistent weak layer we observed in a pit on this same slope 5 days ago, but seems more likely bed surface was above that layer.
MESSAGE
 Comments: Working down west slope on approx 25 degree slope looking for spot to assess slope. Noted wind layer, but thought it was due to exposed terrain at very top of slope. Wind slab noted continuing lower. Should have ended approach to lower parts of slope returning upslope from there knowing wind slab was our primary concern today, but did not give proper gravity to windslab on this slope. Approaching rollover in slightly more open terrain, first skier to attempt to drop a bit lower near rollover to dig pit triggered failure. Two ski partners felt "drop" as failure initiated. Rollover to steeper angle terrain approx 15 to 20 feet below group fractured, with crown following steeper slope angle contour. Propagated approx 75 feet to each side of initiation for 150ft wide crown. No people entrained. Group returned to top of slope, skinning through large trees in lower angle terrain on side of slope. Approach snow was all med water content new snow, no wind slab encountered prior to this event, no other avalanche activity observed.