Northern San Juan
AvalancheKrista Beyer · Feb 5, 2024 · Northern San Juan
Weather
Mild weather with winds out of the south and minor flagging indicating there is still snow available for transport. Clouds were building throughout the day in front of the Pacific storm expected to make landfall in California tomorrow.
Snowpack
We traveled on south, east, and north-facing slopes near and above treeline. On below treeline slopes the snowpack under the new snow felt weak and beat up with thin weak slabs sitting above weaker snow. Near treeline slopes had a thicker slab. The thickness of the slab and the weakness of buried facets depended on the depth of the snowpack. Generally, a deeper height of snow corresponds with a thicker slab and basal facets that are gaining strength whereas a more shallow snowpack corresponds with a thin slab and weaker basal facets. We dug on a southeast slope at about 11,800 ft. Height of snow was around 120cm. About 15 cm of new snow sat above a 4cm crust. Surprisingly this buried crust seemed to be breaking down, perhaps due to how warm the start of the recent storm was. Weak fist hard facets have developed above and below this crust allowing for two weak layers in the top 20cm of the snowpack. Test scores in the attached media indicate that these layers have little current propagation potential, but will easily fail under the anticipated new load. We also dug on a north-facing slope near treeline also at about 11,700 ft. Here the snowpack measured around 170cm deep. Something to note is near and above treeline slopes have significant spatial variability in the depth of snow depending on wind-sheltered or loaded features. Our pit location shows a deeper area of the snowpack. In our pit about 35cm of new drifted snow sat above a finger to pencil hard slab of snow about 50 cm thick. The basal facets that have remained a topic of conversation throughout the season sit about 90cm below the surface and are 4F+. Test indicate no evidence for current propagation potential at any of the weak layers (basal facets in the lower pack or minor wind skim or density changes in the upper pack). The anticipated load from the incoming atmospheric river could easily fail above the slab in the upper pack. Given that our slab is 50cm thick in some of our deepest snowpack areas, the step-down potential is very possible and would create the largest slides we've seen this season.
Avalanche
Small D1 natural off east ridge of Red 1.