April 24, 2008
These curious snow "pillows" were observed following a storm on February 22, 2008, that left 5.4" (13.7 cm) of snow on the ground in Somerset County, New Jersey. That day had a maximum temperature of 35 F (2 C) and a minimum of 24 F (- 4 C). The sky was cloudy throughout. The next day the maximum was 35 F (2 C), with a minimum of 24 F (- 4 C). The photos were taken on February 24, between 11:00 a.m. and noon local time. Approximately 3" (8 cm) of snow was on the ground, with a temperature of 33-35 degrees F (1-2 C). You'll notice that the temperature ranges were the same on the 22nd and 23rd. However, by the 24th, the morning low was 16 F (- 9 C), with clear skies. Temperatures were quite warm on the days prior to the storm. On the 22nd, the snow began falling at 24 F (- 4 C). This precipitation ended as sleet and freezing drizzle in late morning, at which time the temperature reached 32 F (0 C). There was little wind throughout the event or in the days thereafter. The pillows began to be obvious by the late afternoon of the 22nd. They were observed over lawns, concrete, a stone path, and even on a diving board. The exact process of the pillow's formation remains rather mysterious.