Southern San Juan
AvalancheChris Bilbrey · Apr 15, 2023 · Southern San Juan
Weather
Cold, sunny day. Strong westerly winds felt at all elevations. Intense blowing snow along ridgelines that ran out of steam in the afternoon.
Snowpack
Last night's freeze effectively locked up the snowpack, for now at least. We found a hard surface crust ranging from 2 to 4 inches in the valley bottom up to our top-out elevation of about 12,300 feet - moist to wet melt forms below. The snow surface softened and became punchy by midday below about 11,000 feet. Boot penetration increased to around 30 cm on east to south-facing slopes. No rollerball or pinwheel activity on sunny slopes that softened. Surface softening was confined to areas sheltered from the wind. The refrozen surface on wind-ward facing sunny slopes, even at lower elevations, struggled to soften. Above about 11,000 feet, the re-frozen surface stayed intact. Below the new snow, we found evidence of surface moistening/ wetting on northerlies above 12,000 feet from last week's warm up. New snow amounts were tough to gauge as strong winds were quickly re-distributing the snow. Our best guess was around 1 to 2 inches below 10,000 feet, 3 to 4 inches as we approached treeline, and around 8 inches above treeline with drifts pushing a foot deep. Deeper areas above treeline were confined to easterly-facing terrain. The top 10 cm of snow was P- hard (wind-packed rounds) and rested above 4F snow. This hard-over-soft layering was reactive to ski pressure and in quick pits. We consistently observed surface cracking in drifted areas below ridgelines and fresh cornice growth was easy to kick off from above. We triggered several dinner table to VW Bus-sized wind slabs with intentional ski cuts near ridgelines that were mostly D0.5-1 in size, but traveled a respectable distance down the slope. Once we descended further away from the ridgeline, we easily initiated loose dry sluffs on slopes around 35 degrees and steeper. These ran quick and traveled far above the hard, old snow surface. However, none gained enough steam to trench through the re-frozen/ wind layer below. At lower elevations in non-drifted places, the new snow was bonding well to the old snow surface.
Avalanche
Lots of large Loose Wet avalanches on east to south to west-facing slopes, and one size 2.5-3 Wet Slab avalanche on a southeast-facing slope of Baker Peak in Lightner Creek.