Quick report
Altitudes of 4500-7000' had a thick layer of ice (up to several inches thick) with softer snow below. On the ridges, snow on top of the ice layer varied from a fraction of an inch to 16" depending on aspect and aerodynamics. As noted in the "avalanche summary" there was sometimes another wind slab on top of the snow layer that was sitting on the ice. Uphill travel in crampons this morning sometimes produced loud hollow noises from beneath the ice layer, especually when it had a few inches of snow on top. Several times the thick ice layer cracked producing loud (and disturbing)noises. Exposed rocks and the seismograph in this altitude range had 6-8" of clear hard ice. It was probably caused by freezing rain. Above 7000' the frozen rain layer ended and rime ice began. I saw two glide cracks. One was at 7400' on a convex slope above a 30+ degree easy aspect that dropped 100' into a canyon. It was more than 20 feet long and several inches wide. The other was associated with a cornice at 5000'. Off the ridges, there was deep soft snow from treeline to the rim. Up on Monitor ridge, 7600-8250', the wind scour and rime ice was really impressive (see pics). There is no new snow at the Marble Mountain SnoPark (2600') and ski trails in the first mile uphill are often snow free. There is 4-6 feet of snow by 3500. With the ice, scouring, and drifts, the depth of the new snow was hard to determine, but a lot of geography has been buried in the last week. There is several feet of new snow. Weather today: High clouds blocked much of the sunlight. Winds were <10 mph in the morning building to 25 mph at 8250'. The rim temp mid-day was 16 F. Temperatures were below freezing above the treeline all day.
Avalanche
Two small (D1) slab avalanches on east aspects. One at 5800 and one at 6500. They were quite fresh but occurred sometime prior to 07:00 on 12/31. While most snow seemed stable today. There were isolated pacthes with shallow wind slabs 1-3" deep that were very poorly adhered to softer snow below. Four skiers descending from the rim at 13:00 did not trigger any avalanches or signs of instability.