Northern San Juan

Avalanche

Aaron Ball · Mar 8, 2014 · Northern San Juan

View on map

Weather

Skies were mostly sunny all day with calm winds. Air temps was -7 C in the morning, -6 C at 4 PM, and -9 at 6:45 PM.

Snowpack

Three pits were dug today during a Level 2 class: two on N aspects and one on a SE aspect. All were around 11,500 ft in Mineral Basin. Pit #1: North aspect. HS 280cm. Incline 30 deg. Approx 20 cm of storm snow. Snowpack was right side up until approx 85 cm down where resistance changed from pencil above to 4 fingers below. This lower layer was composed of large depth hoar grains. CT17 SP down 27 cm, CT22 SC at 120 cm. Pit #2: North aspect. HS 154cm. Incline 32 deg. Approx 20 cm of new snow starting to decompose with signs of faceting already beginning. Below, facets were mostly observed with progressively harder snow down to approximately 70 cm down where one finger turned to fist+. Below this, depth hoar grains were average of 3 mm with chains stretching as long as 10mm. CT11 RP down 15cm (within recent storm snow), CT12 SP down 25cm (February 27 storm interface), and CT18 SC down 85 cm (large depth hoar grains). Pit #3: SE aspect. HS 111cm. Incline 31 deg. Upper pack was hard layers (1F to K) overlying a 10cm thick fist layer. CT20 RP down 24 cm in this layer. Mid pack was mostly hard layers overlying approx 15 cm of fist hard depth hoar in the lower pack. Depth hoar appeared to be rounding. Temperature gradients supported a rounding regime except within the top 10cm where temp gradient was 4 C per 10 cm. Additional notes: Two rumbling collapses. One was at the bottom of the Front Yard and the other was within the lower portion of Mineral Basin. Both were in locations were surface crusts were present. Radiation Recrystallization was prevalent on solar aspects and north shaded aspects held very cold, loose snow.

Avalanche

3 Loose Wet avalanches were observed on SE aspects, D1-D2. Porphyry Gulch slab avalanche was still visible, as well as another older large D3 avalanche in Mineral Basin on a similar aspect and elevation. Crown in Mineral Basin appeared to be approximately 4-5 feet deep at its deepest.