A north to south gradient in snow totals exists across the San Juan Mountains. The north side of Red Mountain Pass picked up over a foot of new snow while areas south of Red Mountain Pass and in the South San Juan zone received two to six inches. The Sangre de Cristo Range received only trace amounts of snow.
New snow and wind is adding additional stress to buried weak layers. With each loading event in December, numerous human-triggered avalanches were reported in the North San Juan zone on north through northeast to east-facing slopes. Almost all of the avalanches were failing on weak facets found mid-pack or near the ground and formed during dry weather periods in November.
Strong southwest winds prior to the storm shifted to north-northwest with the onset of snowfall, moving snow efficiently near and above treeline. These winds formed fresh, deeper drifts on southwest through southeast to northeast-facing slopes overnight. North and northwest-facing slopes that were loaded prior to snowfall were generally stripped back to the old snow surface.
In wind-loaded terrain, an avalanche you trigger near the surface could step down and break on facets buried deeper and entrain the entire season’s snowpack. Newly formed wind-drifts are overlapping our Persistent Slab avalanche problem on north to east-facing slopes above treeline. Identify wind-loaded terrain features of concern to reduce your risk to avalanches. Wind-drifts on southerly-facing slopes above a firm old snow surface will be easy to trigger from the weight of a rider and move fast.
Stick to slopes angles less than 35 degrees if stability is in question. The snow surface below treeline was very weak prior to the storm. Don’t let your guard down on steeper, treed terrain where new Storm Slabs up to six inches thick could fail on weak snow directly below. You may want to avoid steep slopes that end in terrain traps like gullies or large stands of trees.