Heavy Snow in Northern Coos, New Hampshire

Snow began in the late afternoon and quickly became moderate to heavy in the evening. After midnight warmer air aloft changed some of the precipitation to a mix of snow and sleet. Precipitation quickly ended from west to east early on the morning of the 13th. Snowfall accumulations ranged from 7 to 11 inches in the higher terrain of the eastern North Country, with strong downsloping winds leading to 3 to 5 inch amounts near the Connecticut River.

Early on the 12th surface low pressure formed over the southern Plains, lifting north and strengthening into the Great Lakes. By the evening of the 12th low pressure had deepened to around 995 mb. A warm front extended to the east of low pressure, held in place by a 1038 mb high pressure centered over Quebec. The strong low pressure in the Great Lakes and the exit region of a greater than 100 knot jet streak over the Canadian Maritimes was supporting strong and broad warm air advection over the Northeast. With cold and dry air in place precipitation initially began as snow across northern New England. Secondary low pressure developed off the Mid Atlantic coast and strengthened south of Long Island, ensuring that low level cold air remained in place. Aloft warmer air surged northward, eventually changing precipitation to sleet and freezing rain over much of New Hampshire. Early on the morning of the 13th dry air aloft brought a quick end to precipitation from west to east.