Madison Mysteries: A snow calculator
Somewhat-investigative reports on the oddities of local life
William Thomas Cain
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The mystery: Just how much snow will the average Madisonian shovel in a given winter?
The solution: In some respects, all of this snow shoveling is good for us. The U.S. Surgeon General's Report on Physical Activity and Health in 1996 determined that snow shoveling is intense exercise—about the equivalent of running at 9.3 miles per hour. Unfortunately, as snow shoveling is deceptively strenuous, it’s also a common cause of heart attacks. Whether you're looking for some driveway workouts or just hoping to not die this season, it might help to have a formula for predicting the exact amount of shoveling ahead of you.
According to the National Climatic Data Center, Madison has averaged 44.1 inches of snowfall (including ice pellets and sleet) per year over the last 54 years. Of course, snowfall comes in a range of weights and densities. Shoveling 16 inches of freshly fallen, powdery snow can be easier than shoveling only 6 inches of icy slush. Making calculations even more difficult, if two snowfalls overlap, the resulting "snowpack" may consist of layers of both light and heavy snow.
Years ago, meteorologists attempting to "weigh" snowfall developed the rule of thumb that 10inches of snow would melt down to 1 inch of water. Since water weighs 62.4 pounds per cubic foot they could guess the weight of a snowfall based on the depth of the snow on the ground. Unfortunately, while the 10:1 ratio was nice and easy to work with, it was a flawed measuring device.
When it snows in temperatures around the freezing point, the ratio of snow to liquid water is indeed about 10:1. However, as temperatures, flake structure and wind velocities fluctuate, that ratio may range anywhere from the fabulously fluffy 100:1 to the sopping wet 3:1. In the U.S., the ratio is typically between 8:1 and 20:1, and the current countrywide value set by the US National Weather Service for converting snowfall into its liquid water equivalent in the absence of actual snow samples is 13:1.
So, assuming a 13:1 snow-to-liquid-water ratio and an average snowfall of 44.1 inches, how many tons of the stuff are you moving every year? Let's do the math: Given the weight of water, one inch of average USDA-approved 13:1 ratio snow spread over one square foot of surface would weigh about .42 pounds. So, if you had a 45-foot by 10-foot driveway, or 450 square feet of surface area, a one-inch snowfall would leave you 189 pounds of snow to shovel. And, given our half-century-long average snowfall of 44.1 inches, your driveway would represent 8,334.9 pounds of shoveling per year—about as much weight as a fully loaded Hummer.
Of course, none of this accounts for whatever snowplows jam into the base of your driveway.
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