Quick report
- Collapsing
- isolated
Thoughts based on direct observations over the past few days: There was a piecemeal cycle of increasingly large avalanche activity during the early February Atmospheric River. Pockets of smaller, more isolated activity were observed and reported in the first few days of the storms, while the the largest and most concentrated activity appeared to occur overnight 2/4 into 2/5. (I'm ignoring the early low/middle elevation WRV cycle here, which was a different beast). Prior to 2/4, the slab of storm snow had remained quite soft and poorly internally connected in areas sheltered from the wind. All observed avalanches required a fairly steep slope (35+ish degrees). I saw many large avalanches, and I saw many more starting zones that did not produce avalanches. I observed a few D3s, but most avalanches were smaller than that. Most avalanches were R2-3. I did not observe any R4s. Many starting zones only partially avalached, particularly early in the cycle. Earlier crowns were very ragged and discontinuous, but slides showed more of a persistent slab character as the slab piled up. It was much more difficult to initiate a collapse today than in the previous few days, likely thanks to the thickness and density of the overlying slab. I didn't interpret this as a sign of stability, but it did seem that the likelihood of human triggering had decreased from the previous few day's. I had no interest in entering avalanche terrain that had not produced avalanches. I broke trail through lots of both winded and sheltered terrain, and triggered about 4 relatively small collapses. The largest sounded like it traveled 20-30 feet. I did not see associated cracking in the snowpack. I didn't interpret any of this as a sign of stability, but it does seem that the likelihood of triggering a slide had decreased from the previous few day's. I had no interest in entering avalanche terrain that had not already produced avalanches.
Weather
Windy all day, with extended periods of sun by mid-morning. Nowhere near warm/sunny enough for any significant wet problems in the terrain I traveled through, though the sun may have put a bit of a crust on steep, sheltered slopes directly facing the sun.
Snowpack
Rain crust near the surface exists up to 7,000' or a touch higher, this significantly decreased ski quality down lower. Settled 70-80cm storm snow up higher. New snow still feels a touch inverted thanks to the warmer temps and warmer precip. Lots of wind effect in exposed terrain.
Avalanche
- Size
- D2.5
- Count
- 11
- Aspect
- NW
- Trigger
- N
- Elevation
- 8000 ft
Avalanches in the Pioneers and Boulders grew in size and width over the course of this loading event and ensuing avalanche cycle. The peak of natural avalanche activity seemed to occur overnight 2/4 into 2/5. Prior to this, the slab of storm snow had remained quite soft and poorly internally connected in areas sheltered from the wind. All observed avalanches required a fairly steep slope (35+ish degrees). I saw many large avalanches, and I saw many more starting zones that did not produce avalanches. I observed a few D3s, but most avalanches were smaller than that. Most avalanches were R2-3. I did not observe any R4s. Many starting zones only partially avalached, particularly early in the cycle. Earlier crowns were very ragged and discontinuous, but slides showed more of a persistent slab character as the slab stacked up and then was tied together by the much wetter, denser snow from late in the storm.