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PROFESSIONAL OBSERVATION FORM
 Start Date: 12.15.18 Name: Lundy, VandenBos Operation: SAC
 Drainage/Route:  Beaver Creek Observed Terrain:  7200-9400' - most aspects except W Zone/Region:  Smoky & Boulder Mountains
WEATHER OBSERVATIONS
 HN24: 2-4cm HST: Sky: BKN Precip: Temps:
 Ridgeline Wind: Light
 Blowing Snow: None Snow Available for Transport: Small amounts
 Comments: More clouds than forecast with periods of full overcast.
AVALANCHE OBSERVATIONS
None Reported
 Comments: Numerous small slabs that appeared to have released midstorm - most crowns were partially to completely filled in making details hard to make out. Didn't see anything larger than D1-1.5, but most steep terrain had some evidence of an avalanche.
SNOWPACK OBSERVATIONS
 HS: 40-80cm 
 Upper Pack: 15-20cm: DF F (12/12 storm) 
 Middle Pack: 45cm: FC at top (12/12 FC interface) F - going to 1F at the base of the slab 
 Lower Pack: 10cm: DH 3-4mm F but slightly stronger than what I've seen on Galena Summit 
AVALANCHE PROBLEM ASSESSMENT
Avalanche Characteristics
Character/Avalanche Problem:
Persistent Slab

Layer/Depth:
11/22 / 60cm

Likelihood of Triggering
Sensitivity:
Reactive

Spatial Distribution:
Specific
Terrain
  Primary Concern Comments: Most prominent/reactive on upper elevation northerly aspects
 Comments: Didn't get super high, but didn't see much evidence of wind slab problem. Certainly some snow has moved around with recent wind, but seems to be adding to the persistent slab problem vs. being a problem of its own
STABILITY TESTS
 Stability Test Results: 9000', N, 22*: PST 65/100end; ECTN22,23; CT25 SC
OBVIOUS SIGNS OF INSTABILITY
 Marked with checkmark if observed:
 Cracking (isolated) Depth: 50-60  
 Collapsing (widespread) Depth: 50-60  
 Comments: Had one large rumbling collapse that produced cracks radiating out at least 300' - biggest I've felt in a while! Pretty sure we would have triggered a slide if we were connected to 35+ degree terrain. As it was, a 30 degree adjacent slope cracked but didn't move.
SNOW STABILITY
 Snow Stability Rating for your observed area: Confidence: Trend:
BOTTOM LINE
 Comments: This area representative of our deeper snowpack areas. Basal depth hoar seems slightly stronger here with perhaps a little evidence of compaction, but on the other hand it has a meaty slab above it compared to places like Galena Summit. We avoided being on or under steep terrain.

Snowpack remains a bit thin for off trail riding.
FILE ATTACHMENTS

181215_BeaverCollapse.JPG
As we stood on flat ground, this entire slope progressively collapsed, with visible cracks extending out of the image to the looker's left and through the mid-slope trees at the far side of the slope on the right.

181215_BeaverCollapseAndCracks.jpg
Looking down at the cracks in the slope that collapsed as described in the above picture.

181215_BeaverDepthHoar.JPG
DH