DATE OF OBSERVATION: 01/31/2015
NAME: Zach Guy
ASPECT: NE, E, SE, S, SW, W
ELEVATION: 9,500 – 13,000 ft.
AVALANCHES: On a SE aspect above treeline, we remotely triggered one soft slab from 20 feet away, 3-4″ deep, 30 feet wide. Harmless in size, ran on the the meltfreeze crust. SS-ASr-R1-D1-I. Otherwise, the new snow seemed fairly well bonded to the storm interface, with a few minor sluffs. One south facing basin near Twin Lakes had a significant wet slab cycle, looked to be from the early January warmup, with about 5 wet (ish?) slabs that ran naturally, D2’s in size.
WEATHER: Calm winds in the morning increased by late afternoon to moderate gusts, with snow transport beginning and some plumes off peaks. Overcast and very light snowfall (S-1) in the morning cleared to few clouds by sunset. Warm temps, cooling trend through the day. Felt like the Cascades in the morning.
SNOWPACK: 2-4″ of relatively dense new snow, no wind affect, sitting on the structures described below. Below treeline, the snowpack is entirely fist-hard facets, less than 36″ deep, boot pen to the ground. On southerly tilts, there is a surface melt-freeze crust and a few dacaying crusts in the upper snowpack with facet layers between. On B/N/ATL slopes, the thickest crust we observed was about 6″ thick on a steep, south facing incline, supportive to boot pen. Most crusts were supportive on skis but boots penetrated through.. On near and below treeline aspects where the crust is thin (<2″ thick, on lower angle terrain or more E, SE aspects), we observed widespread localized collapsing and cracking in this surface crust overlying facets, with about 5 rolling collapses that traveled across entire slopes. Wasn’t a concern with only a couple inches of snow above the crust at this point, but a big warning sign for things to come if we get a slab on top. Near and above treeline it was hard to find lingering persistent slab structure. All southerly slopes that we observed were just a stack of decaying crusts with facet layers between. East and northeast aspects N/ATL generally held thin snowpack that was all faceted, F to 4F or so, but specific windloaded features held very hard, relatively small slabs (pencil hard, 6-12″ thick) over facets, and we got 2 collapses on these types of slopes but no avalanches. We avoided a large bowl feature that appeared to have more significant loading through the winter season. It seems the PS here is isolated in location but still possible to trigger if you can find the slab, generally small in size, but could be large on some features.