* Geographic and topographic maps created from the USGS/ESRI ArcGIS mapping software and database
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 Southeast United States. Cold air damming occurs most frequently when a high pressure system centered in the Northeast or Middle Atlantic states tries to circulate dense low-level cold air into the Appalachian Mountains from the east. The mountain barrier inhibits the cold air from moving west so it moves south and southwest along the Foothills, Piedmont, and Coastal Plain to the east. Often the cold air spills into the mountain valleys including cities like Asheville, NC. If rain falls into the cold air, freezing rain occurs if the temperatures are below freezing. Sometimes the vertical temperature profile of the air is cold enough to support snow except in the lowest several hundred to a few thousand feet. In this case, cold air damming can supply the cold air needed at the surface so the snow can reach the ground.
Winston-Salem is in an optimum spot for cold air to get strongly entrenched during cold air damming events. Having lived in North Carolina for twenty-five years, including eighteen years in Winston-Salem, six years in Raleigh, and one year in Asheville, this author has observed numerous freezing rain events associated with cold air damming. Winston-Salem tends to hang on to the freezing rain for several hours longer than other larger Piedmont, Foothills, and Appalachian Mountain cities like Raleigh, Charlotte, Statesville, Greensboro, and Asheville. Winston-Salem is farther north into the low-level flow of cold air plus it is closer to the mountains (other than the city of Asheville actually in the mountains) where shallow cold air gets more tightly entrenched. Warm air from the east, south, or southwest erodes the cold air and changes the precipitation to rain a little earlier in cities farther east or south. Sometimes the cold air is deep enough to support sleet if the snow that is falling through an elevated layer of air above freezing does not completely melt. In this case, cities farther south and east can get more icing with damage to trees and power lines while sleet piles up on the ground in Winston-Salem.
Winston-Salem is part of what this author calls the "Piedmont Ice Storm Zone" which includes the Western Piedmont and the Foothills. This zone extends northeast into Virginia and southwest into upstate South Carolina. The zone also includes Greensboro, Statesville, and Hickory in North Carolina and Danville in the state of Virginia. To a lesser extent, the zone includes Charlotte in North Carolina and Greenville-Spartanburg in South Carolina.
Officially at the Triad International Airport between Winston-Salem and Greensboro, but much closer to Greensboro, the annual mean snowfall is 7.5 inches based on 30-year climatology ending in 2010. Generally over the long term, longer than 30 years, annual snowfall increases a bit to the northwest and decreases to the southeast.
A major snowstorm occurred in the region from December 8 to December 10, 2018. Heavy snow, with snowfall rates of an inch or more per hour, piled up 12 to 15 inches across the city and surrounding communities. Click here to view a short summary of the storm.