MADISON, Wis. (WMTV) -- On any given year, there is a 66 percent chance of a white Christmas in Madison. Chances go up dramatically as you move into central and northern Wisconsin. A "White Christmas" is defined as having at least an inch of snow on the ground on Christmas Day. The record snow depth in Madison on Christmas was 16 inches back in 1985.
Christmas 2019 is looking at much lower chances than normal of snow on the ground. While the pattern will remain rather active around the area, most of the snow will fall north and south of the region. While not zero, it is going to take some big changes in the current forecast to assure a White Christmas.
A Brown Christmas across Wisconsin may become more likely in the years ahead as the world warms. The overall area of North America covered by snow is decreasing. One reason is because an increasing percentage of winter precipitation is falling as rain instead of snow in many locations. Our partners at Climate Central report found that between sea level and 5,000 feet in elevation across the Western U.S., a smaller percentage of winter precipitation is falling as snow.
However, the relationship is more complex at each local level. Rising temperatures can cause some individual storms to produce more snow, where temperatures are still well enough below freezing. That’s because for every 1°F rise in temperature, the atmosphere can hold 4 percent more water vapor. In turn, more water is available to fall as snow or rain.
This illustrates the probability of 1”+ of snow depth based on analysis of the 1981-2010 NOAA/NCEI climatological normal. Record snow depth comes from the Applied Climate Information System. North American Snow Cover data is from Rutgers University Global Snow Lab. Data improved in 1973, when satellite resolution was upgraded for suitable snow depth mapping accuracy.