Southern San Juan
SnowpackChris Bilbrey · Apr 8, 2020 · Southern San Juan
Weather
Warm and sunny. Got down right hot in wind-sheltered areas and at lower elevations. Alpine winds were just enough to keep your gloves close and need an extra layer.
Snowpack
Last night's weak freeze had varying impacts on below treeline slopes. Stronger radiational cooling contributing to a harder snow surface observed in wider, more open areas with direct view of the sky. Snow surfaces on heavily treed slopes were weaker and hollow. As we climbed higher in elevation, we found more supportable snow surfaces near and above treeline. In the alpine, southerly-facing slopes are developing corn conditions on the surface with a stiff and generally stronger snowpack underneath. Extensive wetting observed at lower elevations does not appear to be a widespread concern at present in the alpine, but that could change with continued warm weather in the forecast. However, we found evidence of vertical water percolation between 10 and 20 cm's deep depending on aspect and location. Wet snow issues are not out of the question in the alpine with numerous loose wet slides running out of steep, rocky terrain. Buried persistent weak layers on east and west-facing slopes in the alpine are rounding and were non-reactive in multiple ECTs. Two near-surface facet layers within the top meter seem like they need a very large trigger like a cornice fall to fail. There is more and more evidence of this behavior throughout the San Juan Mountains during our current warm period with a few cornice falls producing wide propagating avalanches. By our exit late afternoon, southerly-facing slopes below treeline were down right sloppy and full depth rotten. Extra caution should be exerted if you have to travel on lower elevation slopes that face east through south to west.