Red Cone: New Snow and Snowpack Tests

Submission Info
Monday, February 26, 2018 - 12:00pm
Red Flags: 
Recent loading by new snow, wind, or rain
37° 35' 44.52" N, 119° 1' 33.6" W
Snowpit Observations
More detailed information about the snowpack: 

Toured up Red Cone to test northerly aspect facet layers prior to new loading and look for new wind slab formation. Hand shears between 9400' and 10400' on NE-N-NW aspects in wind deposits from the past few day failed on isolation or with easy force, though often under very thin wind slabs (see photo). The structure of the upper snowpack in these shears was generally wind deposited rounds, on top of wind brokend fragments that were faceting, on top of a thin layer of near surface facets, on top of an old melt-freeze crust. Several kick tests on previously wind loaded features had some localized cracking or small cornice failures but no triggered slides (see photo). Some localized cracking around our skis as more new snow fell by around noon, but no shooting cracks or collapsing.

Two sets of snowpack tests near treeline at ~10,150'. 1st site on a NE aspect on a 12 degree slope where snow depth was 140cm: CTE PC down 9cm in the F hard decomposing recent storm snow on top of 4F wind broken snow, CTM RP down 43cm in F hard facets under 1F hard wind deposited rounds, CTM SP in the same layer, ECTN 11 in the 43cm deep facets. 2nd site on a NW aspect on a 24 degree slope where snow depth was 93cm: CTM SC down 17cm in F hard facets under 4F hard wind deposited rounds, ECTN 9 in both F+ hard decomposing fragments over 4F hard wind deposited round and in the 17cm deep facets, PST 30/100 SF in the 17cm facet layer. Snow temperatures taken at the 2nd site because previous wind deposits were sitting right on top of near surface facets and I wanted to see if the temp gradient would be weakening the facet layer: Tsurf = -5.5, T-10 = -8, T-20 = -8, T-30 = -7, T-40 = -6.

There was evidence of some recent (2/23 or 24?) D1 wind slab releases at the top of Red Cone Bowl. Visibility was poor, but from what I could see the crowns (2 slides) were 15cm deep, the weak layer was facets, and the bed surface was an old melt-freeze crust that was solid ice is several places.

Snow began to fall today at 945am down at 8600' (S-1). By 1015am at 8950' snow was coming down a little harder (S1). By 1045am at 9370' snowfall was moderate (S2) which was the rate that was maintained for the rest of the time we were there. Light winds on the Tamarack ski trails before heading up the skin track, but then the first notable wind was at 10,100' at 1110am when it was light from the SW. Wind at the top was light from the E-NE with moderate gusts. Visiblity was poor from moderate snowfall, but not a lot of visible wind transport. Skinning across Horseshoe Lake on the way back, winds funneling out of Mammoth Pass were strong and blowing snow was moderate. Plenty of wind slab building, and slabs cracking, around Horseshoe. Winds also seemed to be picking up as we continued down with plenty of drifting. Wind directions were varriable. Temps were very cold all day.

Snowpack photos: 
Hand Shears in thin wind slabs failing on isolation
Most exciting kick test of the day: small cornice failure, S facing
Weather Observations
Blowing Snow: 
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