Observation: Cottonwood Canyons

Observation Date
12/20/2021
Observer Name
Hardesty
Region
Salt Lake » Cottonwood Canyons
Location Name or Route
Cottonwood ridgeline
Weather
Sky
Clear
Wind Speed
Calm
Weather Comments
Clear and calm. Warm.
Snow Characteristics
Snow Surface Conditions
Faceted Loose
Melt-Freeze Crust
Damp
Snow Characteristics Comments
Snow surfaces on the shady aspects are weakening with the clear and cold. Off aspects are crusted but softening with the midday thaw.
Red Flags
Red Flags
Poor Snowpack Structure
Red Flags Comments
Even though there have been recent avalanches, cracking, collapsing, wind loading etc, etc; I did not personally observe any red flags today.
Comments
I did remotely trigger a cornice overhanging the Silver Fork headwall on the ridgewalk today, but the dining room table cornice did not trigger an avalanche below. Photo below.

I was able to view a bit of the range today with clear skies and a good monocular. I was surprised to see how much snow remained on the hillsides. In other words, it didn't appear we went through a significant natural avalanche cycle last week; rather it was enough to make the snowpack conditionally unstable....just waiting for a trigger. And we have a lot of triggers in the Wasatch. While the current poor structure remains dangerous, it is clearly not as hair-trigger as it was late last week into Saturday. Perhaps - as Greg wrote on Friday - this may lure people into thinking things are safer than they are. They are not.

My concerns then, heading into the holdays with a series of storms on tap are - well - that we may have the perfect storm for more close calls and accidents or worse. Some conjecture below -
  • Repeater avalanches may be possible with the heavy snowfall and wind. Many of the avalanches either did not take out all of the PWL at the bed surface....and/or the decomposing thin/friable crust with facets above/below will not hold much of a load.
  • On slopes that didn't avalanche, the slab hardness is trending One Finger>Pencil and I fear that with enough loading (heavy snowfall and wind), we may see much larger avalanches propagating over wide distances. By then the slab depth may average 3-5' deep.
  • We'll be keeping an eye on the weakening surface snow in the coming day(s). It may be that the new snow bonds poorly on the shady slopes.
We'll see. Big picture - we expect the danger to ramp up again in the coming days.
Today's Observed Danger Rating
Considerable
Tomorrows Estimated Danger Rating
None
Coordinates