Northern San Juan
AvalancheColin Mitchell · Feb 10, 2019 · Northern San Juan
Weather
Clear, cold and blustery. Winds increased through the day, and were strong by the time I got to the trailhead. Wind loading was most prevalent near and below treeline, alpine fetchs have largely been stripped.
Snowpack
Recent and ongoing winds have had a significant effect on the snowpack above treeline. The snow surface varied between knife-hard chalky wind slabs, wind crusts, and facets. Lots of drifting and slab formation across the terrain. Cornices have grown this week, and were sensitive, with several small failures visible in this area. The mid-pack continues to consolidate and gain strength. The recent snow/old snow interface was at a melt-freeze crust. No faceting or weak snow was noted here. Lower down, the Jan 18th interface was easy to spot, and consisted of 4f-hard facets sandwiched between 3 thin melt-freeze or ice crusts. This interface was not reactive to snowpack tests, but is the likely failure layer for recent very large avalanches on southerly and westerly aspects. The basal facets are still easily visible at the ground, but are rounding, and becoming less reactive to tests. See profile for details. A little minor cracking in thin wind slabs, otherwise no collapsing, whumpfing or other signs of instability observed.
Avalanche
No new activity observed other than a few cornice chunks