What determines the total snowfall for a storm?

Dear Tom,
We recently had multiple waves of snow in Chicago. What determines the total snowfall for a storm?
— David A. Chicago
Dear David,
A great question after a period of rapid-fire snow events. There is often a debate on whether multiple-day or, in some cases, same-day snowfalls are part of the same storm, and there are no hard-and-fast rules. Sometimes there is a lull in the snow for a few hours before it resumes, and it is usually considered one storm. In Chicago, there is occasionally a break between the “system” snow and the lake-effect snow, and that is usually considered to be part of the same storm. A few years ago, a group of forecasters did an in-depth review of Chicago’s greatest snowstorms and in some instances added snowfall before or after the main event to storm totals, and in other cases determined that these snows were separate entities.
There is often a debate on whether multiple-day or in some cases, same-day snowfalls are part of the same storm, and there are no hard-and-fast rules.