Northern San Juan
SnowpackChris Bilbrey · Apr 10, 2023 · Northern San Juan
Weather
Hot, sunny day with a light breeze near and above treeline. Today's breeze did not prevent the inevitable surface warming and wetting.
Snowpack
Despite last night's marginal freeze, we found good supportive surfaces this morning. Boot penetration (BP) started out 15 to 20 cm across many aspects below treeline, decreasing in depth the higher we climbed. By the time we reached the alpine around 10 AM, BP was about 10 cm. A snowpit on an east-facing slope at 11,300 feet revealed two concerning layers of poly grains within the top 2 to 3 feet below the surface. Snowpack test yielded ECTP 21 and CT RP 12/15 breaking in wet grains around 45 cm down. This layer was refrozen today, but the individual bonds between grains was difficult to identify. This is probably the Wet Slab avalanche layer of concern that could more easily be impacted by a rider, or has higher odds to fail naturally. We identified another moist, poly grain layer down around 75 cm, but the individual bonds were still visible and this layer seemed less reluctant to fail in test. We did observe failure with harder force in the deeper layer from additional loading taps after the failure closer to the surface. Height of snow at this location was about 240 cm, and the slab below the wet, moist layers ranged K- to P hard below about 140 cm (we did not dig much deeper than about 100 cm). The upper slab around the layers of concern that failed in test ranged P- to 1F. We observed several surface cracks walking across flatter terrain and some cracks traveled around 30 feet in front of our skis. Cracking did not make a loud whump as we often experience during the winter, but the surface made the "snap, crackle, pop" sound when the crack occurred. Northerly-facing slopes near and above treeline still harbored cold, dry snow, and "hot pow" existed on the same slopes below treeline. We found hard, wind-stiffened snow near ridgelines that did not extend very far down the slope. We exited the mountains around 2 PM and it was almost a bit too late. Sunny slopes below treeline were quickly becoming trap door. Our ski tails easily sunk into wet, rotten snow while descending below about 11,000 feet back to the highway.