Gunnison
SnowpackJohn MacKinnon · Feb 4, 2013 · Gunnison
Weather
Broken skies with thin clouds, mild temperatures and light westerly winds
Snowpack
We observed several shooting cracks and rumbling collapses on SE aspects below treeline. Cracks propagated up to 10 meters but nothing moved. Sunny aspects had a thin crust on top of old storm snow. Shady slopes had a mix of surface facets and isolated areas of surface hoar. We remote triggered a sizeable soft slab avalanche while skinning up a ridge at 11,000 feet on an East aspect. The initial slide was triggered from about 5 meters away and broke on a steep >40 degree convex roll. The crown was 40 cm of 4F- snow and the slide broke on the 1/23 facet layer. A quick fracture line profile revealed 40 cm of recent storm snow and 60 cm of facets. This slide broke 25 meters across the slope and slid 150 meters downhill. Another slide released just after this slide. On further inspection we noticed a crack that traveled along the ridge-top; it looked like the crack connected the two slides from over 100 meters. This slide also broke on a steep E aspect at 11,000 feet. This slide was over 100 meters wide and ran 200 meters down slope and slid on facets. We estimated that this was one single event--SS-ASr-R2-D2.5-O--as we skied down the crowns looked to be connected. Overall size of the slide looked to be 125m wide and 200 meters vertical. Impressive propagation as it initially traveled around a corner and out of our sight. This slide did knock over a few small trees with debris almost up to a meter on the road cut and behind trees. While skiing down we remote triggered another slide on a steep east facing convex roll at 10,800 ft. This was triggered from a bench just above the roll just after we heard a loud collapse. The slide ran 150 meters down hill and was 15 meters wide. It broke on facets as well. Crown heights were ~40 cm. SS-ASr-R1-D1.5-0. After our descent much of the basin we skied in was covered in debris. All triggered slides were in areas that had not seen much prior wind-loading. We were all surprised by the propagation potential of soft (4F- to F+) persistent slabs