Snow Impacts on Society

Discussion

The rate at which snow falls can be just as important for travel as the total amount that falls in a storm. On the evening of Saturday, January 1, 2005, Duluth, Minnesota rang in the New Year with a fireworks display nature style. Thundersnow dumped 6 inches of dense moisture-laden snow in two hours at the National Weather Service Office. Snowfall rates of 3 inches or more an hour are not unprecedented for strong convective snow bursts but are rare for any specific location. For about 20 minutes the snow was so intense and the visibility so low that the city government ordered snow removal vehicles off the road because of the weather conditions. The heavy snow fell from roughly 6:30 PM to 8:30 PM. If the snow had fallen Friday Evening New Year's Eve or between 6 AM and 6 PM on a weekday the impact would have been even more significant. Lighter snow that accumulates to high totals over a several day period can still cause problems especially if strong winds produce a lot of drifting.

The National Weather Service uses certain criteria to indicate how much snowfall is typically needed to cause major travel problems or economic disruption. The snowfall amounts and the length of time over which the snowfall occurs are both incorporated into the thresholds. In most of the Middle and Upper Mississippi Valley, snowfall of 6 inches or more in 12 hours or 8 inches or more in 24 hours triggers a warning for heavy snow. Slightly lighter snow totals are covered by an advisory. The lighter totals may still trigger a warning if combined with other elements like very strong winds, heavy sleet, or enough freezing rain to damage tree limbs and power lines.

Warning criteria vary depending upon how much experience a region has in dealing with snow. Note the following list of thresholds used by the National Weather Service in different parts of the country.

Marquette, Michigan
   8 inches in 12 hours
   10 inches in 24 hours

Duluth, Minnesota
   6 inches for an event rather that in a specified period of time
   Previous criteria was 6 inches in 12 hours and 8 inches in 24 hours
   New criteria effective in October 2023 (notification)

Memphis, Tennessee
   4 inches in 12 hours
   6 inches in 24 hours

Huntsville, Alabama
   2 inches in 12 hours...That's just flurries!
   4 inches in 24 hours

Literature

Call, D. A., 2005: Rethinking snowstorms as snow events: A regional case study from Upstate New York. Bull. Amer. Meteor. Soc., 83, 37-51.

Kocin, P. J., and L. W. Uccellini, 2004b: A snowfall impact scale derived from Northeast storm snowfall distributions. Bull. Amer. meteor. Soc., 85, 177-194.