Northern San Juan
AvalancheLuke Ochs Chris Bilbrey · Nov 25, 2018 · Northern San Juan
Weather
Clear skies, cool temps and light northerly winds. Newly wind-drifted snow observed from Saturday night's storm. Up to 12 inches of snow fell in the North San Juan zone over the past 72 hours with strong westerly and northerly winds.
Snowpack
Snow surface was a mixture of newly fallen snow, stiff wind-drifts, and surfaces scoured by recent winds. Wind-drifts were more widespread and deeper on slopes near and above treeline facing northeast through east to south. Observed isolated audible collapses in wind-loaded spots below ridgelines and in cross-loaded terrain features near and above treeline. Below treeline we observed soft storm slabs with no cracking or collapsing. Stability test on a wind-loaded slope produced propagating test results.
Avalanche
Skier 2 triggered the avalanche while skiing an adjacent, lower angled slope. Slope angle at site of initiation was approx. 30 degrees and failure propagated uphill and to the skiers left into steeper terrain (approx. 35 degrees). Slope to the right of the trigger location did not avalanche. Avalanche crown depth was thinnest where skier initiated failure (approx. 6 inches) with the remainder of crown depth averaging 10 to 25 inches deep. Terrain feature producing the avalanche was a cross-loaded convex roll.