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Winston-Salem is located in the western piedmont of North Carolina. Because of a weather process know as cold air damming, the city is one of the most freezing rain and sleet prone parts of the United States. Cold air damming occurs most frequently when a high pressure system centered in the Northeast or Middle Atlantic states tries to rotate cold air into the Appalachian Mountains. The mountain barrier inhibits the dense cold air from moving west so it moves south and southwest along the piedmont to the east. Often the cold air spills into the mountain valleys including cities like Asheville. If warm air moves over the cold air and rain falls from the warmer air into the cold air, freezing rain and sleet occur. Sometimes the vertical temperature structure of the air can be cold enough for snow except in the lowest several hundred to several thousand feet. Cold air damming can supply the cold air near the surface necessary to allow the snow to reach the ground without melting.
Having grown up in Winston-Salem, this author has seen numerous ice storms where this town was one of the last locations in North Carolina to loose it's cold air. Charlotte, Raleigh, Statesville, and even Greensboro not far to the east change to rain as a warm front approaches from the south or southeast. Winston-Salem hangs on to the freezing rain just one more hour or two then surrenders to the warm air. This author calls the section of the western piedmont and adjacent foothills where cold air gets locked in particularly tight, the "Piedmont Ice Storm Zone". This zone includes cities like Greenville, SC, Charlotte, NC, Hickory and Statesville, NC, Winston-Salem and Greensboro, NC, and Danville, VA.