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PROFESSIONAL OBSERVATION FORM
 Start Date: 02.25.19 Name: Davis Operation: SAC
 Drainage/Route:  Durrance Shoulder Observed Terrain:  6300-8300' Zone/Region:  Smoky & Boulder Mountains
WEATHER OBSERVATIONS
 HN24: 25 cm HST: 40 cm Sky: OVC Precip: S1 Temps:
 Ridgeline Wind: Moderate and Steady from the SW
 Blowing Snow: I Snow Available for Transport: Large amounts
 Comments: Wind speed increased throughout the morning. Wind was transporting small amounts of snow at lower elevation near the SNRA by 1300. Perfect loading wind speeds and intense transport >8,000'. Whiteout conditions with ski track filling in within 10 min. High moisture snow was riming the snow surface.
AVALANCHE OBSERVATIONS
 No. Location Date Size Type Trigger Aspect Elevation Comments
 1 Durrance Today N >8,300' I heard a sizeable natural avalanche around 1200. Unclear where it ran (no vis) but based on the loading pattern it was likely either the main bowl of Durrance or the E face above Headquarters.
SNOWPACK OBSERVATIONS
 HS: 130 cm on SE @ 6,600' 
 Upper Pack: 130-90 storm snow 
 Middle Pack: Some wind packed layers. (2/2) at 60 cm 
 Lower Pack: Stout MFcr at 35 cm, below that 1F FC/DH to the ground. 
AVALANCHE PROBLEM ASSESSMENT
Avalanche Characteristics
Character/Avalanche Problem:
Wind Slab

Layer/Depth:
40-60 cm

Likelihood of Triggering
Sensitivity:
Touchy

Spatial Distribution:
Specific
Terrain
  Primary Concern Comments: Intense wind loading along the ridge >8,000'
 
Avalanche Characteristics
Character/Avalanche Problem:
Storm Slab

Layer/Depth:
10-30 cm

Likelihood of Triggering
Sensitivity:
Stubborn

Spatial Distribution:

Terrain
  Problem 2 Comments: In more sheltered terrain <7,000'. Failures occurred in a density change about 30 cm deep just above the new/old interface. Denser snow today was building a 10-20 cm 4F- thin slab at the surface. This problem wasn't a concern yet, but should be on the radar with more precip.
STABILITY TESTS
 Stability Test Results: ECTN in storm slab density change. CPST 37/90 End down 100 in the top end of basal FC and DH.
OBVIOUS SIGNS OF INSTABILITY
 Marked with checkmark if observed:
 Cracking (isolated) Depth: 40-60 cm Length: ski length
 Comments: Cracking in fresh 1F- wind slab along the ridge >7,500'.
SNOW STABILITY
 Snow Stability Rating for your observed area: Confidence: Trend:
 Comments (aspects and elevations of instability, etc): Very poor stability in wind-affected terrain, moving quickly toward poor stability in more sheltered terrain. Poor visibility and avoidance of avalanche terrain make it difficult to assign a danger rating. Gut feelings: HIGH danger seems like an easy call at upper elevation. The exposed middle elevation terrain I observed was headed toward HIGH quickly if not already there. Areas at middle and lower elevations without active wind-loading didn't quite have a thick or dense enough slab to pose much threat.
BOTTOM LINE
 Comments: At low elevation the fledgling storm slab shows indications that it'll be quiet touchy as we thicken the slab. Intense wind loading, cracking and a large sounding natural avalanche was plenty of evidence to point toward very poor stability and dangerous avalanche conditions in wind-loaded terrain.