Matt Greisman, in Elkridge, writes: "In Monday's paper, there are three days in a row that show: chance of storms, isolated storms, and scattered storms. Is there any real difference?" Not much. The National Weather Service glossary defines "isolated" as connoting at least a 10 percent chance of measurable precipitation in any one spot. "Scattered" generally suggests a stronger chance than "isolated." Some may use it for storms scattered over time, not area. "Chance" has no clear meaning beyond "more than zero" likelihood.