Observation: Stairs Gulch 3/5/2011

Observer Name: 
Havlick/Primomo
Region: 
Salt Lake
Big Cottonwood Canyon
Stairs Gulch
Observation Date: 
03/05/2011
Location or Route: 
Tanners to Stairs
Weather
Sky: 
Overcast
Wind Direction: 
Southwest
Wind Speed: 
Light
Weather Comments: 

thickening overcast while we were out (0600-1400).  Around 1230 snow showers, and more visible wind transport along high peaks were noted.  Temps were mild, with noticeably intense long/shortwave radiation.  Did not seem to have much effect on snow at mid and high elevations we travelled.

Snow Characteristics

New Snow Density: 
Medium
Snow Surface Conditions: 
Powder
Dense Loose
Wind Crust
Melt-Freeze Crust
Rain-Rime Crust
Damp
Snow Characteristic Comments: 

Interesting  and mostly pleasant snow conditions.  Solar and reflected radiation did not seem to have much effect on snow at mid and high elevations we travelled.  South facing Tanners, even by noon, was still settled pow. 

Ran across some scattered hard windslab on terrain scoops, ridgelines, predicable places.  See video. 

Witnessed a startling natural soft slab/sluff cascade with a large amount of force and mass behind it.  Believe windloading from the light/moderate, steady SW wind was the culprit.  Initiating the slide by cornice fall or just overload on the precarious graupel layer resting neatly above the suncrust and below the most recent 6in++ storm snow.  Our shovel tilt tests had this layer failing with isolation on a 35º slope, S facing, ~10500ft. (below Tanners/Broads notch)

In Broads Fork, below exposed MLK raincrust, huge 10mm (saying 1cm isnt as impressive) latticed scrolls were common.  With the added dense windslab, we were spooked off certain shots due to the poor structure characteristics.

 

Red Flags

Recent Avalanches
Wind Loading
Cracking
Red Flag Comments: 

witnessed a recent avalanche likely from windloading.  Had cracking wind slabs underfoot on test slopes

Primary Concern

Primary Concern: 
Wind Slabs
Probability: 
Moderate
Aspect: 
North
Northeast
East
Southeast
Elevation: 
High
Mid
Trend: 
More Dangerous
Primary Concern Comments: 

danger and consequences increasing with more wind.

Secondary Concern

Secondary Concern: 
Deep Slabs
Probability: 
Low
Aspect: 
North
Northeast
East
Elevation: 
High
Mid
Trend: 
More Dangerous
Secondary Concern Comments: 

danger increasing w/ new load possibly reactivating facets below MLK rain crust.

snow_profile_location: 
Comments - Photos - Videos (group 1)

attempt to backlight cross section of sample of exposed rain crust, with hue faceted lattice structure below it.

IMG_0628.JPG
Video 1: 
Printer-friendly version
Observed Danger Rating: 
Moderate
Forecast Danger Rating: 
Moderate

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