Northern San Juan
AvalancheAnonymous · Jan 28, 2017 · Northern San Juan
Weather
Sunny, cold, gentle N. winds
Snowpack
Skinned up and skied down southeast aspect above treeline. In general the new snow was firm and well bonded with little wind effect. However, lots of major cross loading from the south, and pockets of windslab and shallow snow.
Avalanche
Remote triggered a small wind slab avalanche on an east aspect, above treeline, in cross loaded terrain from winds out of the south. Before dropping into SE aspect, skier took one step down, jumped on 32 degree slope, and huge rumbling whoompf and collapse sent cracks shooting across slope, where they released on a more easterly feature around 35 degrees. Hard wind slab, roughly 2.5 ft deep crown, about 50 feet across, ran 200-300 feet down the slope until coming to a stop, as terrain below was only about 30 degrees. Seemed to run on an old wind surface. Skier was not entrained. Did not encounter or observe drifted snow from the more recent north winds. More disconcerting was the visuals of large and very large wind slab avalanches observed across the valley on N and NW aspects above treeline. In Corkscrew gulch, the N and NW slopes on the ridge between Red 1 and 2 observed a Wind Slab avalanche that propagated all the way around the basin, starting below the ridge crest, with huge crowns estimated from miles away at 10+ feet. Guessing R3-D3. Probably in excess of 1500 feet across and over 1000 foot runout into the basin. Propagated across many start zones and terrain features. Also observed wind slab avalanche on a NW aspect on Brown Mountain above Albany Gulch in cross loaded terrain. Looked to have run days ago, but cleaned out the entire above treeline slope. Guessing 300 feet across and 800+ feet runout into a gully.