Professional Observation

Observation Details

Signs of Unstable Snow

Snow Stability

Key Points

Wind speeds picked up in the town of Mammoth after writing the forecast this morning and continued to climb at Mammoth Mountain as well. By 7:15 a.m. there were gusts up to 152 mph at the top of Ch. 1!

I went for an afternoon tour into the Mammoth Lakes Basin to assess wind transported snow above tree-line. Skies were mostly clear all afternoon.

• At 1:15 p.m. leaving the TH winds were strong out of the SW with a temp of 39f.
• Approaching Red Cone any E thru S aspects had moist and sticky surface snow, or had already begun to refreeze into varying degrees of breakable crust by 3:15.
• Sheltered N aspects are holding cold, dry surface facets up to mid-boot depth in some locations.
• At 3:15 p.m. at 10,400′ ATL, winds were strong, gusting to extreme speeds coming from the S with an air temperature of 28f.
• Looking up and down the Mammoth Crest there was very little (if any) snow transport at the ridgetop, but plenty of blowing snow on mid-slope terrain features. At a distance most of this appeared to be in a state of turbulent suspension, but I wouldn’t be surprised if there are some isolated pillows building where the wind is eddying in small, confined terrain features.
• On the ridge approaching Red Cone there was minimal blowing snow. Any fresh looking deposits I observed were well below the ridgetop on NW thru NE aspects.
• Most of Red Cone Bowl is stripped down to old, firm snow with the crown from a small slide a couple of weeks ago still obvious.
• I dropped into Red Cone Bowl on firm surfaces and found a smooth, somewhat punchy wind deposit under a rock band on a due N aspect at 10200′ and chose to dig a quick pit to see what this fresh wind loaded panel was resting on. HS was 155 cm.  The fresh wind deposit was about 5 cm thick and 1F- hard, resting on a 20 cm layer of 4F hard storm snow from our last snowfall. Both of these layers overlaid F hard facets. Test results: CT2Q1SP down 5cm at interface of new wind skin and old storm snow, and CT16Q2RP within the old storm snow. Even a shovel shear test did not produce clean results between the 4F soft slab overlying the F hard old faceted snow. Good news for now, but this interface will be on my radar.
• I did find several cross loaded areas low in the Red Cone Bowl that were unreactive to ski testing. Many wind deposits that I found even well below ridgetops were quite supportable and showing no obvious signs of instability. However, I also avoided traversing low beneath the aprons of rock bands and small chutes where I observed active wind transport fearing that I could find a shallow spot that would produce a small slide in the terrain above me.
• Skiing in sheltered and confined N facing terrain below tree-line I was able to initiate some small, but fast running surface sloughs consisting of dry surface facets.