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Observation: Abajos

Observation Date
12/1/2019
Observer Name
Travis Nauman
Region
Abajos
Location Name or Route
Ridge north of old ski area
Weather
Sky
Few
Wind Speed
Calm
Weather Comments
Beautiful day with no wind and clouds slowly increasing into the afternoon.
Snow Characteristics
Snow Surface Conditions
Powder
Dense Loose
Snow Characteristics Comments
The snow was still pretty soft from the storm cycle that ended Saturday morning. Surprisingly the wind did not impact most of the ridge line we worked today. This is probably due to us being on the down wind side of the Abajos. Overall, the snow felt quite supportable while touring and was still quite fun to ski! There was a slight suncrust starting to form on aspects that got some sun yesterday.
Red Flags
Red Flags
Collapsing
Poor Snowpack Structure
Red Flags Comments
We observed one somewhat subtle collapse while gaining the ridge on a north face. However, despite the snow feeling pretty supportable while touring, our snowpit told a different story. An initial CT test failed on isolation on depth hoar ice crystals that ranged from 2-5 mm, but were irregular in shape and size - this layer was 0-15 cm and was under about 70 cm of snow for a total snow depth of 80-90 cm. We continued the test on the same column and had a gradual planar failure at CT4-6 at 67 (bottom of Friday night snow?) cm up from the ground and another CT20 sudden planar failure at 47 cm. We repeated the CT test and had a CT4 sudden planar again at 67 on a small grapple layer and then a CT10 sudden planar/collapse at the depth hoar. There was some serious ice crystal development at the ground - a mix of grass and subshrubs. These results were on a 27 degree slope, aspect of 40 (NE) at about 9000 feet. We stayed in low angle meadows skiing and don't think it wise to go on or under anything 30+ degrees right now until things settle out. I am calling the danger considerable on these areas because I think human triggered avalanches would be very likely on steeper slopes, however, I think naturals would be highly unlikely without a weather change.
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Same
Problem #1 Comments
Unfortunately, the failure at the ground on ice crystals reads like a PWL to me... The crystals were not uniform and might be starting to bond, so it's not a classic depth hoar, hopefully there is enough snow depth for this to settle out and further bond sooner rather than later, but only time will tell. However, a failure on this layer seems more than possible right now and would be devastating.
Avalanche Problem #2
Problem
New Snow
Trend
Decreasing Danger
Problem #2 Comments
The last storm slab is still reactive on grapple layers that probably fell during some of the high intensity cells that came through in this last storm. These are still highly reactive and a failure of this layer might trigger the depth hoar layer.
Forecaster note: This is valuable if not alarming information. In my travels to the Abajos yesterday I found a deep, strong, non-reactive snowpack in my test area on a NW aspect around 10,000'. Wind and elevation have created a snowpack with widely varying depths, and spatial variability will be a key factor as we continue to assess the stability. For now, we have a limited data set, but due to the differences in our stability tests, I lean towards this problem as being more isolated than widespread, and hence indicative of a MODERATE danger. We will have to gather more data before a confident forecast can be delivered.
Today's Observed Danger Rating
Considerable
Tomorrows Estimated Danger Rating
Considerable

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