29 Dec - Inversion
I saw this cool raicho today (ptarmigan in English). They hang out under the snow quite well hidden, then suddenly burst out of seemingly gentle powder and give you a hell of a fright. Anyway, the striking inversion, see picture below, across what appeared to be all of Nagano probably kept temperatures at valley bottom much lower than was forecast . I was measuring +4C at 1700m, +1.5 at 2400m, yet the high at 800m was only +2.5. My highest point was 2400m, winds were light to moderate, sun was strong, snow quality was ok. Solar aspects have been baked and were setting up a nice new breakable surface crust by afternoon.
With clear skies there was a lot of radiation cooling taking place with the snow surface remaining a lot cooler than the air temperatures on shaded slopes in the alpine.
I saw one Size 2 natural slab avalanche that started about mid-slope on a steep convex bowl at 2400m. Plus I was able to very easily trigger Size 1.5 loose snow avalanches on steep sunny terrain in the early afternoon. Had the slope been bigger, the resulting avalanche would have been equally bigger.
Did anyone see any avalanche activity at lower altitudes today? Edit: plenty reported from Happo. One detail below.