Active wind loading in the Horse Creek Drainage

SNOWPACK OBSERVATION
Horse Creek Drainage, beneath the Matterhorn
Submission Info
Volunteer Observer
Monday, January 20, 2020 - 3:00pm
Red Flags: 
Recent loading by new snow, wind, or rain
38° 6' 4.5684" N, 119° 22' 48.27" W
Snowpit Observations
More detailed information about the snowpack: 

Went for a tour in the Horse Creek Drainage up towards the Matterhorn, spent one night at the lower edge of enjoyable skiing terrain at 8400', skied around yesterday 1/19 and today 1/20. 

Yesterday was warm and overcast all day with a few S gusts.  We were able to skin from the end of the road at Mono Village following an existing skin/snowshoe track.  We would not have been able to do so without this last storm on 1/17.  The trail that switchbacks above the lake and into the main canyon was snow covered and esay to skin up, not as easy to ski down.  4-6" had fallen on 1/17, but there is not yet enough snow to ski all the way down freely- lots of sage, rocks, and downed trees barely visible.  We went as far as the moraine below the Matterhorn at 10,700' with thoughts of Ski Dreams, the wide NE facing couloir off the E ridge of the Matterhorn.  The couloir looked plenty filled in, but with late hour we opted to save it for the next day.  On north aspects we encountered 20cm of denser 4 finger (4F) hard wind deposited snow over 15cm fist (F) hard storm snow above firm pencil (P) hard windboard.  When we broke through the windboard, we often found loose unconsolidated faceted snow.  Hand shears failed with moderate force below the windboard in the softer fist hard storm snow, sometimes resistant planar and sometimes an irregular break.  I stomped on some small convex rolls with no results- no movement or cracking.  Dug in at 10,600' and performed some stability tests- compression test failed in the F snow 20cm down (CT13Q2) and below a crust 45 cm down (CT28 Q1); extended column test identited the same layers with no propogation.  More interestingly, on an E aspect, we found the same upper structure (15cm 4F wind desposited over 10cm F hard) over a series of melt freeze (MF) crusts and facets.  Several hand shears failed on isolation below the first MF crust.  HS ranged from 90-200cm on E aspects around 9800'.  Both N and E aspects skied similarly- dense bouncy turns that were consistently a little grabby and occasionally more grabby.  The sky cleared up by dark.  

We heard a couple gusts of wind in the middle of the night and in the morning started up the same route towards the Matterhorn again greeted by consistent moderate S winds.  We saw snow transport at 9000' and above.  Reaching the same high point below the Matterhorn at 10,700' strong S gusts and transport over the ridges made us suspect some fresh sensitive windslabs forming in the couloir, so we left it for another day.  We skied back down, up the main drainage a bit, and skied a lower angle N facing bowl lower down.  At our high point in the bowl at about 10,400', we found fresh 5cm windslab that failed with light force in hand shears.  On the ski out, we saw significant wind transport filling in our old ski and skin tracks down to below 8,000. The ski out down low was sporty with no skiable terrain but the louge track of a trail.  

 

Snowpit or crown profile photo or graph: 
Snowpack photos: 
-- placeholder --

ESAC receives significant financial support from ...