Mammoth Area - Sherwins -Reactive wind slab

Mammoth Rock- Sherwins
Submission Info
Sunday, March 1, 2020 - 11:30am
Sherwins 37° 36' 34.5996" N, 118° 59' 32.1936" W
Snowpit Observations
More detailed information about the snowpack: 

Looking as the Mammoth area received the most snow from the early morning storm, we headed to the Sherwin ridge above Mammoth Rock to primarily check on new snow instabilities. It was nice to be out with snow falling and cold temperatures. New snow depths steadily increased with the ascent from 15cm at the trailhead to upwards of 30cm above 9400ft and in the deepest wind loaded areas just adjacent to ridgeline there was upwards of 40cm of new snow. The new snow was very light and low density, but had enough water content that it was already bonding fairly well to the old hard snow surfaces and staying put where not sheltered and non-wind affected. The more wind affected snow adjacent to ridge top transitioned from soft Fist hardness snow on the top 20cm to almost 4F hardness snow on the lower half of the new deposition, it was reactive and slid easily on old slick surfaces.

My first stomp on the ridgeline cornice produced a sensitive soft slab that ranged from 30-40cm crown depth, propagated 35ft in width and slid 100ft or so down slope, piling a decent amount of debris up against some small trees. The volume was enough that it could have drug a skier down and partially buried them. Bigger terrain and starting zones today could have certainly produced enough volume that a rider could have been buried. There was also some evidence of small natural activity that had released on the leeward side of ridgeline on the northerly aspects.  Crowns looked to be 20-30cm deep with short running distances of 50ft or so.

We topped out at 1130 under light falling snow, 16degF temperatures and relatively light WSW winds. As we grabbed some food and traversed the ridgeline winds lulled, the light WSW wind pattern abated by the time we were ready to ski, and a 15mph N wind had started blowing. When we came back up to the top later around 1230, the north wind was blowing steadily at a moderate 25mph velocity and was already starting to strip the wind loaded areas of the northerly aspects.  The NE aspects up high were wind loaded the most and were reactive to ski cuts producing small D1 soft slabs. The due north aspects were less wind affected and stayed put upon ski cuts and stomping. The new snow was quite light and you felt the hard bottom with every ski turn. We did not experience any significant sloughing, even on higher 30deg slope angles. The .5” Snow Water Equivalent in the storm snow seemingly gave it just enough body to begin sticking even to the hardest of surfaces.

We did not observe any collapsing or significant cracking during our travels.  Likely not enough weight in the new snow to affect underlying poor structure, but I imagine a larger slide in bigger terrain would tear out some of the underlying faceted weak snow that abounds throughout the range.  Storm slab did not seem to be an issue in the area we skied today. Wind loading and stiffening wind slab at ridge line was the main hazard in the area we visited today.

Snowpack photos: 
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