Southern San Juan
AvalancheChris Bilbrey · Apr 2, 2024 · Southern San Juan
Weather
Splitter bluebird day. Light to moderate north wind in the morning. Around Noon, wind speeds decreased dramatically.
Snowpack
We found 6 to 8 inches of new snow near and below treeline. This is sitting above a firm crust on southeast through south to west-facing slopes - we easily broke through the crust with ski boots. The crust was generally an inch thick with re-frozen melt-forms below. This weaker snow was 4F to 1F- (top to bottom), and could come into play with a fresh pulse of meltwater during a big warm-up. On northerly-facing slopes, the new snow sits above a thin layer of near-surface facets (0.5 mm). Digging on a north-facing slope at 11,800 feet, we observed mixed results at this faceted interface, ECTP 10 & ECTN 11. Hardness profile of the new snow was F>4F>1F. Digging deeper, we found a rounding surface hoar layer around 40 to 45 cm deep. This layer was easily identifiable in pit walls. However, we only observed ECTN 22 x 2. This pit location was right at the upper terminus of timberline. Our next pit location was on an east-facing slope at the same elevation (11,800 feet). Below the new snow resides a half-inch, breakable crust with faceting above and below. We observed ECTP 16 & ECTN 18 in near-surface facets (0.5-1.5 mm) above the crust - no results below the crust. Facets below were slightly smaller (0.5-1 mm). Below the Mfc/ FC combo is a 1F to P hard slab. No evidence of buried surface hoar in our east-facing snowpit. Boot penetration range 30 to 50 cm across aspects and elevation. As the morning progressed, the sun was quickly consolidating the new snow on east through south-facing slopes. We noticed subtle cracking in drifted areas where the new snow was getting thicker. Descending more sun-exposed slopes midday, we observed minor sheeting of the new snow above the buried crust (a few small rollerballs), but this seems like a brewing concern with more sun and warmer temperatures. Very little snow transport above treeline onto leeward slopes except on the highest peaks. Shady aspects at all elevations held cold, winter-like snow.
Avalanche
Loose Dry avalanches triggered by morning sun, and one skier-triggered slide (D1) that failed at the new-old interface. The new-old interface produced mixed results (ECTP and ECTN) in snowpack tests higher on the slope.