Southern San Juan
AvalancheChris Bilbrey · Feb 14, 2023 · Southern San Juan
Weather
Snowing and blowing all day. Snowfall rates ranged from S1 to S2 with moments of S3 to S5. Generally, light winds at lower elevations once we got out of the main valley but became more noticeable around 11,000 feet. Shortly after 3 pm, wind speeds increased, mixing to lower elevations and drifting the new snow below the treeline.
Snowpack
New snow totals ranged from 30 cm around 10,000 feet up to 50 cm near the treeline at 11,400 feet. The storm snow fell right side up with a denser layer (1F-) of snow at the new/ old interface and the snow got progressively lower in density toward the surface. We observed generally good bonding to a firm melt-freeze crust on south, southwest, and west-facing slopes below the treeline but this is likely to change with additional snow volume. We found a more reactive storm slab on northerly, east, and southeast-facing slopes below and near the treeline. The storm snow consistently failed and propagated with 11 to 13 taps in either a layer of near-surface facets (4F-) or below a faceted crust. Fractures we're planar and snappy. By the afternoon, the top 8 to 12 inches of new snow easily sluffed on slopes and terrain features approaching 35 degrees. Additionally, snowpit tests produced easy-force progressive collapse failures in CTs or ECTNs in the lower-density surface snow. This suggests that triggering a long-running surface sluff could provoke a deeper, larger failure. As we approached the treeline, we started observing cracks in the snow next to our skin track and the snow had a more slabby feel. While approaching the edge of a wind-drifted area on an east-facing slope, we triggered a slide from about 50 feet away. The slide broke into weak faceted grains (4F-) below a thin crust. We were surprised this slide did not trigger the bigger, steeper slope below which ran naturally around the New Year.
Avalanche
No new avalanches were observed but obscured skies prevented views into bigger terrain. Loose Dry avalanches were easy to provoke on slopes and terrain features approaching 35 degrees - these are likely to increase in volume and sensitivity from additional snow volume.