Close
PROFESSIONAL OBSERVATION FORM
 Start Date: 04.12.19 Name: Lundy Operation: SAC
 Drainage/Route:  Iron/Goat Divide Observed Terrain:  6500-9100', primarily N-E-SE Zone/Region:  Sawtooth Mountains
WEATHER OBSERVATIONS
 HN24: Tr HST: Sky: BKN Precip: Temps:
 Ridgeline Wind: Light and Gusty from the W
 Blowing Snow: M Snow Available for Transport: Small amounts
 Comments: Morning was FEW to SCT skies. Weather became more squally after 1230 with brief periods of S1 and clouds, then back to BKN skies. Accumulation was minimal. Ridgetop winds were gusting to MOD with some wind transport taking place - see photo below.
AVALANCHE OBSERVATIONS
None Reported
 Comments: Evidence of a number of midstorm avalanches, some storm or wind slabs (~D2) up high and wet loose in steep areas. Nothing too dramatic or different than what's already been reported.
SNOWPACK OBSERVATIONS
 HS: Dug at 8100' on a NNW aspect. HS was 245cm. The entire snowpack was moist to wet in this location - no dry snow. 
 Upper Pack: Full mixed bag of surface conditions - very dependent on aspect and elevation. Below about 8000', surfaces on all aspects were MFcr with a good freeze about 10cm thick. Snow below the crust was wet. HST gradually increased on the MFcr above 8000' up to 25cm at 9000'. 4/6 MFcr became softer and thinner as it became more insulated by the HST. Above 8500', HST on shady slopes seemed dry and relatively unaffected by rain. On solars, there was a breakable crust at the surface and moist or wet snow below that down to the 4/6 MFcr.  
 Middle Pack: In the pit at 8100', NNW the midpack was 1F but moist to wet. I didn't observe any flow channels while digging. 
 Lower Pack: Bottom 30cm of old basal FC were wet with some evidence of pooling moisture. They seemed fairly weak - F to 4F. I honestly wasn't that excited to be where I was once I saw them. 
AVALANCHE PROBLEM ASSESSMENT
Avalanche Characteristics
Character/Avalanche Problem:
Wind Slab

Layer/Depth:
Forming today: 15-20cm?

Likelihood of Triggering
Sensitivity:
Not Observed

Spatial Distribution:
Isolated
Terrain
  Primary Concern Comments: Old wind slabs were very stiff and seemed unreactive. Concern was new wind slabs forming today. There's not much SAFT but it was still moving. I couldn't get anywhere where I felt comfortable ski cutting or stomping.
 
Avalanche Characteristics
Character/Avalanche Problem:
Wet Loose

Layer/Depth:


Likelihood of Triggering
Sensitivity:
Stubborn

Spatial Distribution:
Specific
Terrain
  Problem 2 Comments: Low and mid elevation solars softened enough to be a concern on some steeper slopes. Upper elevations did not seem to be an issue.
 
Avalanche Characteristics
Character/Avalanche Problem:
Dry Loose

Layer/Depth:
15-25cm

Likelihood of Triggering
Sensitivity:
Reactive

Spatial Distribution:
Isolated
Terrain
  Problem 3 Comments: At least from 8500-9000', the HST was sluffing easily on the 4/6 MFcr on shady slopes where it was still dry
STABILITY TESTS
 Stability Test Results:
SNOW STABILITY
 Snow Stability Rating for your observed area: Confidence: Trend:
 Comments (aspects and elevations of instability, etc): Main concerns were wet loose at mid and low elevations, and small wind slabs up high. Problems are easily recognized and avoided.
BOTTOM LINE
 Comments: Still curious what's happening between 9000-10000' in the Sawtooths. I could see things being a bit different up higher. A solid day of warming and sunshine will unglue a fair bit of snow on upper elevation solars.
FILE ATTACHMENTS

190412_iron_cr_wind_loading.jpg
Wind transporting snow onto a NE aspect at 9000 feet.